> ## Documentation Index > Fetch the complete documentation index at: https://docs.iotools.cloud/llms.txt > Use this file to discover all available pages before exploring further. # Fuel Economy Calculator > Convert fuel economy between MPG (US/UK), L/100km and km/L, then estimate trip fuel cost, compare two vehicles side by side, and project annual fuel spend with a CO₂ emissions estimate. [Try Fuel Economy Calculator in your browser →](https://iotools.cloud/tool/fuel-economy-calculator/) ## OpenAPI ````yaml https://api.iotools.cloud/v1/openapi post /v1/tool/fuel-economy-calculator openapi: 3.1.0 info: title: iotools.cloud API version: 1.0.0 description: >- Run any iotools.cloud tool over HTTP. Authenticate with `Authorization: Bearer iot_live_…`. **Only `POST /v1/tool/{slug}` costs credits.** Every GET here — the catalog, a tool's schema, your balance — is free. A tool call is charged its own weight or your plan's per-call minimum, whichever is larger; `x-iotools-credit-cost` on each operation is quoted at the free-tier minimum, and `GET /v1/tools/list` returns the exact figure for your key. `GET /v1/me/credits` reports what you have left, and `GET /v1/me/usage` reports what it went on. Failures are RFC 9457 problem documents — branch on `code`. servers: - url: https://api.iotools.cloud description: Production security: - bearerAuth: [] tags: - name: Catalog description: Find a tool and read its contract. Free. - name: Converters description: >- Convert between formats, encodings, and units — Base64, CSV and JSON, timestamps, and more. Fast, free, and processed right in your browser. - name: Formatters description: >- Format, beautify, minify, and validate code and data — JSON, HTML, CSS, SQL, and regex. Clean up messy input in one click, with nothing to upload. - name: Generators description: >- Generate exactly what you need and on demand — passwords, UUIDs, QR codes, hashes, random numbers, and more. Secure, instant, and free. - name: Calculators description: >- Crunch the numbers fast — from everyday math to specialized conversions and unit work. Free online calculators that run entirely in your browser. - name: Editors description: >- Edit and transform text, code, and images with quick, focused editors that run entirely in your browser — nothing to install, and no sign-up needed. - name: Utilities description: >- Everyday developer and web utilities — DNS and IP lookups, redirect and certificate checkers, and other quick diagnostics. Free and privacy-friendly. - name: Account description: Your key's allowance, limits and usage history. paths: /v1/tool/fuel-economy-calculator: post: tags: - Calculators summary: Fuel Economy Calculator description: >- Convert fuel economy between MPG (US/UK), L/100km and km/L, then estimate trip fuel cost, compare two vehicles side by side, and project annual fuel spend with a CO₂ emissions estimate. [Try Fuel Economy Calculator in your browser →](https://iotools.cloud/tool/fuel-economy-calculator/) operationId: run_fuel_economy_calculator requestBody: required: false content: application/json: schema: type: object properties: fuelEconomy: type: number description: Fuel Economy minimum: 0 fuelEconomyUnit: enum: - mpg_us - mpg_uk - l100km - kml description: Unit currency: type: string description: Currency Symbol tripDistance: type: number description: Distance minimum: 0 tripDistanceUnit: enum: - km - miles description: Distance Unit tripFuelEconomy: type: number description: Fuel Economy minimum: 0 tripFuelEconomyUnit: enum: - mpg_us - mpg_uk - l100km - kml description: Economy Unit tripFuelPrice: type: number description: Fuel Price minimum: 0 tripFuelPriceUnit: enum: - liter - gallon_us - gallon_uk description: Price Unit compareVehicle1: type: number description: Vehicle 1 Economy minimum: 0 compareVehicle1Unit: enum: - mpg_us - mpg_uk - l100km - kml description: Vehicle 1 Unit compareVehicle2: type: number description: Vehicle 2 Economy minimum: 0 compareVehicle2Unit: enum: - mpg_us - mpg_uk - l100km - kml description: Vehicle 2 Unit compareDistance: type: number description: Distance minimum: 0 compareDistanceUnit: enum: - km - miles description: Distance Unit compareFuelPrice: type: number description: Fuel Price (per Liter) minimum: 0 annualMileage: type: number description: Annual Distance minimum: 0 annualMileageUnit: enum: - km - miles description: Distance Unit annualFuelEconomy: type: number description: Fuel Economy minimum: 0 annualFuelEconomyUnit: enum: - mpg_us - mpg_uk - l100km - kml description: Economy Unit annualFuelPrice: type: number description: Fuel Price minimum: 0 annualFuelPriceUnit: enum: - liter - gallon_us - gallon_uk description: Price Unit annualFuelType: enum: - gasoline - diesel description: Fuel Type required: [] examples: 30_mpg_us_car_convert_trip_compare_and_annual: summary: 30 MPG (US) car — convert, trip, compare and annual value: fuelEconomy: '30' fuelEconomyUnit: mpg_us currency: $ tripDistance: '500' tripDistanceUnit: km tripFuelEconomy: '8' tripFuelEconomyUnit: l100km tripFuelPrice: '1.50' tripFuelPriceUnit: liter compareVehicle1: '30' compareVehicle1Unit: mpg_us compareVehicle2: '45' compareVehicle2Unit: mpg_us compareDistance: '10000' compareDistanceUnit: km compareFuelPrice: '1.50' annualMileage: '15000' annualMileageUnit: km annualFuelEconomy: '8' annualFuelEconomyUnit: l100km annualFuelPrice: '1.50' annualFuelPriceUnit: liter annualFuelType: gasoline 45_mpg_us_diesel_miles_per_gallon_price: summary: 45 MPG (US) diesel, miles + per-gallon price, £ value: fuelEconomy: '45' fuelEconomyUnit: mpg_us currency: £ tripDistance: '300' tripDistanceUnit: miles tripFuelEconomy: '45' tripFuelEconomyUnit: mpg_us tripFuelPrice: '6.50' tripFuelPriceUnit: gallon_us compareVehicle1: '25' compareVehicle1Unit: mpg_us compareVehicle2: '6' compareVehicle2Unit: l100km compareDistance: '12000' compareDistanceUnit: miles compareFuelPrice: '1.80' annualMileage: '12000' annualMileageUnit: miles annualFuelEconomy: '45' annualFuelEconomyUnit: mpg_us annualFuelPrice: '6.50' annualFuelPriceUnit: gallon_us annualFuelType: diesel km_l_input_other_sections_empty: summary: km/L input, other sections empty value: fuelEconomy: '15' fuelEconomyUnit: kml currency: $ tripDistance: '' tripFuelEconomy: '' tripFuelPrice: '' compareVehicle1: '' compareVehicle2: '' compareDistance: '' compareFuelPrice: '' annualMileage: '' annualFuelEconomy: '' annualFuelPrice: '' responses: '200': description: Tool output content: application/json: examples: 30_mpg_us_car_convert_trip_compare_and_annual: summary: 30 MPG (US) car — convert, trip, compare and annual value: tool: fuel-economy-calculator tool_version: 1.0.1 outputs: conversionTable: - unit: MPG (US) value: '30' - unit: MPG (UK) value: '36.03' - unit: L/100km value: '7.84' - unit: km/L value: '12.75' tripTable: - metric: Distance value: 500 km (310.69 miles) - metric: Fuel needed value: 40 L (10.57 US gal) - metric: Total cost value: $60 - metric: Cost per km value: $0.12 - metric: Cost per mile value: $0.1931 compareTable: - metric: Distance value: 10,000 km - metric: Vehicle 1 value: 7.84 L/100km - metric: Vehicle 1 fuel value: 784.05 L - metric: Vehicle 1 cost value: $1,176.07 - metric: Vehicle 2 value: 5.23 L/100km - metric: Vehicle 2 fuel value: 522.7 L - metric: Vehicle 2 cost value: $784.05 - metric: Result value: Vehicle 2 saves $392.02 (33.3%) annualTable: - metric: Annual distance value: 15,000 km (9,320.59 miles) - metric: Fuel consumed value: 1,200 L (317.01 US gal) - metric: Annual cost value: $1,800 - metric: Monthly cost value: $150 - metric: Fuel type value: Gasoline/Petrol - metric: CO₂ factor value: 2.31 kg/L - metric: Annual CO₂ value: 2,772 kg (2.77 tonnes) credits_used: 3 credits_remaining: null 45_mpg_us_diesel_miles_per_gallon_price: summary: 45 MPG (US) diesel, miles + per-gallon price, £ value: tool: fuel-economy-calculator tool_version: 1.0.1 outputs: conversionTable: - unit: MPG (US) value: '45' - unit: MPG (UK) value: '54.04' - unit: L/100km value: '5.23' - unit: km/L value: '19.13' tripTable: - metric: Distance value: 482.8 km (300 miles) - metric: Fuel needed value: 25.24 L (6.67 US gal) - metric: Total cost value: £43.33 - metric: Cost per km value: £0.0898 - metric: Cost per mile value: £0.1444 compareTable: - metric: Distance value: 19,312.08 km - metric: Vehicle 1 value: 9.41 L/100km - metric: Vehicle 1 fuel value: 1,816.99 L - metric: Vehicle 1 cost value: £3,270.59 - metric: Vehicle 2 value: 6 L/100km - metric: Vehicle 2 fuel value: 1,158.72 L - metric: Vehicle 2 cost value: £2,085.7 - metric: Result value: Vehicle 2 saves £1,184.88 (36.2%) annualTable: - metric: Annual distance value: 19,312.08 km (12,000 miles) - metric: Fuel consumed value: 1,009.44 L (266.67 US gal) - metric: Annual cost value: £1,733.33 - metric: Monthly cost value: £144.44 - metric: Fuel type value: Diesel - metric: CO₂ factor value: 2.68 kg/L - metric: Annual CO₂ value: 2,705.3 kg (2.71 tonnes) credits_used: 3 credits_remaining: null km_l_input_other_sections_empty: summary: km/L input, other sections empty value: tool: fuel-economy-calculator tool_version: 1.0.1 outputs: conversionTable: - unit: MPG (US) value: '35.28' - unit: MPG (UK) value: '42.37' - unit: L/100km value: '6.67' - unit: km/L value: '15' tripTable: - metric: Distance value: '-' - metric: Fuel needed value: '-' - metric: Total cost value: '-' - metric: Cost per km value: '-' - metric: Cost per mile value: '-' compareTable: - metric: Distance value: '-' - metric: Vehicle 1 value: '-' - metric: Vehicle 1 fuel value: '-' - metric: Vehicle 1 cost value: '-' - metric: Vehicle 2 value: '-' - metric: Vehicle 2 fuel value: '-' - metric: Vehicle 2 cost value: '-' - metric: Result value: '-' annualTable: - metric: Annual distance value: '-' - metric: Fuel consumed value: '-' - metric: Annual cost value: '-' - metric: Monthly cost value: '-' - metric: Fuel type value: '-' - metric: CO₂ factor value: '-' - metric: Annual CO₂ value: '-' credits_used: 3 credits_remaining: null schema: type: object required: - tool - tool_version - outputs - credits_used - credits_remaining properties: outputs: type: object properties: conversionTable: type: array description: Fuel Economy Conversion items: type: object properties: unit: type: string description: Unit value: type: string description: Value x-iotools-columns: - unit - value tripTable: type: array description: Trip Cost items: type: object properties: metric: type: string description: Metric value: type: string description: Value x-iotools-columns: - metric - value compareTable: type: array description: Vehicle Comparison items: type: object properties: metric: type: string description: Metric value: type: string description: Value x-iotools-columns: - metric - value annualTable: type: array description: Annual Cost & CO₂ Estimate items: type: object properties: metric: type: string description: Metric value: type: string description: Value x-iotools-columns: - metric - value tool: type: string description: The tool's slug, echoing the {slug} in the request path. tool_version: type: string description: Output-contract version for this tool. credits_used: type: integer description: >- Credits this call consumed, after any settlement refund. 0 when metering is disabled. credits_remaining: type: - integer - 'null' description: >- Credits left in the current monthly allowance, or null when metering is disabled. request_id: type: string description: Correlation id, also sent as x-request-id. '400': $ref: '#/components/responses/ValidationError' '401': $ref: '#/components/responses/Unauthorized' '402': $ref: '#/components/responses/InsufficientCredits' '403': $ref: '#/components/responses/ToolNotAllowed' '404': $ref: '#/components/responses/ToolNotFound' '413': $ref: '#/components/responses/PayloadTooLarge' '429': $ref: '#/components/responses/RateLimited' '500': $ref: '#/components/responses/ToolFailed' '503': $ref: '#/components/responses/ToolDisabled' security: - bearerAuth: [] components: responses: ValidationError: description: Invalid request. content: application/problem+json: schema: type: object description: >- RFC 9457 problem document, served as application/problem+json. Branch on `code`; `title` is human prose and may be reworded without notice. Some failures add extension members — `fields` on validation errors, `retry_after` on 429s, `credits_used`/`credits_remaining` on billing-adjacent failures — documented on the responses that carry them. required: - type - title - status - code properties: type: type: string format: uri description: Stable documentation URI for this failure. examples: - https://iotools.cloud/docs/errors/validation_error title: type: string description: Short human-readable summary of the failure. examples: - Invalid request status: type: integer description: HTTP status code, matching the response's own status. code: type: string description: >- Stable machine-readable error code — branch on this, not `title`. enum: - validation_error detail: type: string description: Human explanation of this occurrence. request_id: type: string description: Correlation id, also sent as x-request-id. fields: type: - object - string additionalProperties: type: string description: >- What failed: a map of field name → message. Absent when the body itself is malformed; a single string when the failure isn't tied to one field. example: type: https://iotools.cloud/docs/errors/validation_error title: Invalid request status: 400 code: validation_error detail: One or more inputs are invalid — see `fields`. request_id: e4042b29-8f1e-4c7a-9b52-6f0d1a3c7e11 fields: inputString: Required Unauthorized: description: Missing or invalid API key. content: application/problem+json: schema: type: object description: >- RFC 9457 problem document, served as application/problem+json. Branch on `code`; `title` is human prose and may be reworded without notice. Some failures add extension members — `fields` on validation errors, `retry_after` on 429s, `credits_used`/`credits_remaining` on billing-adjacent failures — documented on the responses that carry them. required: - type - title - status - code properties: type: type: string format: uri description: Stable documentation URI for this failure. examples: - https://iotools.cloud/docs/errors/invalid_api_key title: type: string description: Short human-readable summary of the failure. examples: - Invalid API key status: type: integer description: HTTP status code, matching the response's own status. code: type: string description: >- Stable machine-readable error code — branch on this, not `title`. enum: - invalid_api_key detail: type: string description: Human explanation of this occurrence. request_id: type: string description: Correlation id, also sent as x-request-id. example: type: https://iotools.cloud/docs/errors/invalid_api_key title: Invalid API key status: 401 code: invalid_api_key detail: 'Provide ''Authorization: Bearer ''.' request_id: e4042b29-8f1e-4c7a-9b52-6f0d1a3c7e11 InsufficientCredits: description: Monthly credit allowance exhausted. content: application/problem+json: schema: type: object description: >- RFC 9457 problem document, served as application/problem+json. Branch on `code`; `title` is human prose and may be reworded without notice. Some failures add extension members — `fields` on validation errors, `retry_after` on 429s, `credits_used`/`credits_remaining` on billing-adjacent failures — documented on the responses that carry them. required: - type - title - status - code properties: type: type: string format: uri description: Stable documentation URI for this failure. examples: - https://iotools.cloud/docs/errors/insufficient_credits title: type: string description: Short human-readable summary of the failure. examples: - Insufficient credits status: type: integer description: HTTP status code, matching the response's own status. code: type: string description: >- Stable machine-readable error code — branch on this, not `title`. enum: - insufficient_credits detail: type: string description: Human explanation of this occurrence. request_id: type: string description: Correlation id, also sent as x-request-id. credits_used: type: integer description: Always 0 — a refused call charges nothing. credits_remaining: type: integer description: Credits left in the allowance — fewer than this call costs. example: type: https://iotools.cloud/docs/errors/insufficient_credits title: Insufficient credits status: 402 code: insufficient_credits detail: This call costs 1 credit and 0 remain in this month's allowance. request_id: e4042b29-8f1e-4c7a-9b52-6f0d1a3c7e11 credits_used: 0 credits_remaining: 0 ToolNotAllowed: description: Tool exists but has no API surface. content: application/problem+json: schema: type: object description: >- RFC 9457 problem document, served as application/problem+json. Branch on `code`; `title` is human prose and may be reworded without notice. Some failures add extension members — `fields` on validation errors, `retry_after` on 429s, `credits_used`/`credits_remaining` on billing-adjacent failures — documented on the responses that carry them. required: - type - title - status - code properties: type: type: string format: uri description: Stable documentation URI for this failure. examples: - https://iotools.cloud/docs/errors/tool_not_allowed title: type: string description: Short human-readable summary of the failure. examples: - Tool not available over the API status: type: integer description: HTTP status code, matching the response's own status. code: type: string description: >- Stable machine-readable error code — branch on this, not `title`. enum: - tool_not_allowed detail: type: string description: Human explanation of this occurrence. request_id: type: string description: Correlation id, also sent as x-request-id. example: type: https://iotools.cloud/docs/errors/tool_not_allowed title: Tool not available over the API status: 403 code: tool_not_allowed detail: >- "Background Remover" is available on iotools.cloud but has no API endpoint. request_id: e4042b29-8f1e-4c7a-9b52-6f0d1a3c7e11 ToolNotFound: description: No such tool. content: application/problem+json: schema: type: object description: >- RFC 9457 problem document, served as application/problem+json. Branch on `code`; `title` is human prose and may be reworded without notice. Some failures add extension members — `fields` on validation errors, `retry_after` on 429s, `credits_used`/`credits_remaining` on billing-adjacent failures — documented on the responses that carry them. required: - type - title - status - code properties: type: type: string format: uri description: Stable documentation URI for this failure. examples: - https://iotools.cloud/docs/errors/tool_not_found title: type: string description: Short human-readable summary of the failure. examples: - Tool not found status: type: integer description: HTTP status code, matching the response's own status. code: type: string description: >- Stable machine-readable error code — branch on this, not `title`. enum: - tool_not_found detail: type: string description: Human explanation of this occurrence. request_id: type: string description: Correlation id, also sent as x-request-id. example: type: https://iotools.cloud/docs/errors/tool_not_found title: Tool not found status: 404 code: tool_not_found detail: No tool with that slug. See GET /v1/tools/list. request_id: e4042b29-8f1e-4c7a-9b52-6f0d1a3c7e11 PayloadTooLarge: description: Body too large. content: application/problem+json: schema: type: object description: >- RFC 9457 problem document, served as application/problem+json. Branch on `code`; `title` is human prose and may be reworded without notice. Some failures add extension members — `fields` on validation errors, `retry_after` on 429s, `credits_used`/`credits_remaining` on billing-adjacent failures — documented on the responses that carry them. required: - type - title - status - code properties: type: type: string format: uri description: Stable documentation URI for this failure. examples: - https://iotools.cloud/docs/errors/payload_too_large title: type: string description: Short human-readable summary of the failure. examples: - Payload too large status: type: integer description: HTTP status code, matching the response's own status. code: type: string description: >- Stable machine-readable error code — branch on this, not `title`. enum: - payload_too_large detail: type: string description: Human explanation of this occurrence. request_id: type: string description: Correlation id, also sent as x-request-id. example: type: https://iotools.cloud/docs/errors/payload_too_large title: Payload too large status: 413 code: payload_too_large detail: Request body exceeds this tool's size limit. request_id: e4042b29-8f1e-4c7a-9b52-6f0d1a3c7e11 RateLimited: description: Per-minute rate limit exceeded. headers: Retry-After: description: Seconds to wait before retrying (RFC 9110 delta-seconds). schema: type: integer content: application/problem+json: schema: type: object description: >- RFC 9457 problem document, served as application/problem+json. Branch on `code`; `title` is human prose and may be reworded without notice. Some failures add extension members — `fields` on validation errors, `retry_after` on 429s, `credits_used`/`credits_remaining` on billing-adjacent failures — documented on the responses that carry them. required: - type - title - status - code properties: type: type: string format: uri description: Stable documentation URI for this failure. examples: - https://iotools.cloud/docs/errors/rate_limited title: type: string description: Short human-readable summary of the failure. examples: - Rate limit exceeded status: type: integer description: HTTP status code, matching the response's own status. code: type: string description: >- Stable machine-readable error code — branch on this, not `title`. enum: - rate_limited detail: type: string description: Human explanation of this occurrence. request_id: type: string description: Correlation id, also sent as x-request-id. retry_after: type: integer description: >- Seconds until the window resets — the same value as the `Retry-After` header. example: type: https://iotools.cloud/docs/errors/rate_limited title: Rate limit exceeded status: 429 code: rate_limited detail: Too many requests. Retry in 30s. request_id: e4042b29-8f1e-4c7a-9b52-6f0d1a3c7e11 retry_after: 30 ToolFailed: description: Tool failed to run. content: application/problem+json: schema: type: object description: >- RFC 9457 problem document, served as application/problem+json. Branch on `code`; `title` is human prose and may be reworded without notice. Some failures add extension members — `fields` on validation errors, `retry_after` on 429s, `credits_used`/`credits_remaining` on billing-adjacent failures — documented on the responses that carry them. required: - type - title - status - code properties: type: type: string format: uri description: Stable documentation URI for this failure. examples: - https://iotools.cloud/docs/errors/processing_error - https://iotools.cloud/docs/errors/internal_error title: type: string description: Short human-readable summary of the failure. examples: - Tool failed to run - Internal error status: type: integer description: HTTP status code, matching the response's own status. code: type: string description: >- Stable machine-readable error code — branch on this, not `title`. enum: - processing_error - internal_error detail: type: string description: Human explanation of this occurrence. request_id: type: string description: Correlation id, also sent as x-request-id. credits_used: type: integer description: >- Always 0 on `processing_error` — a failed run is refunded, floor included. credits_remaining: type: integer description: >- Credits left after the refund. Absent when metering is disabled. example: type: https://iotools.cloud/docs/errors/processing_error title: Tool failed to run status: 500 code: processing_error detail: The tool failed to run. Please try again. request_id: e4042b29-8f1e-4c7a-9b52-6f0d1a3c7e11 credits_used: 0 ToolDisabled: description: Tool temporarily disabled. content: application/problem+json: schema: type: object description: >- RFC 9457 problem document, served as application/problem+json. Branch on `code`; `title` is human prose and may be reworded without notice. Some failures add extension members — `fields` on validation errors, `retry_after` on 429s, `credits_used`/`credits_remaining` on billing-adjacent failures — documented on the responses that carry them. required: - type - title - status - code properties: type: type: string format: uri description: Stable documentation URI for this failure. examples: - https://iotools.cloud/docs/errors/tool_disabled - https://iotools.cloud/docs/errors/api_unconfigured title: type: string description: Short human-readable summary of the failure. examples: - Tool temporarily disabled - API not configured status: type: integer description: HTTP status code, matching the response's own status. code: type: string description: >- Stable machine-readable error code — branch on this, not `title`. enum: - tool_disabled - api_unconfigured detail: type: string description: Human explanation of this occurrence. request_id: type: string description: Correlation id, also sent as x-request-id. example: type: https://iotools.cloud/docs/errors/tool_disabled title: Tool temporarily disabled status: 503 code: tool_disabled detail: This tool is temporarily unavailable. Try again shortly. request_id: e4042b29-8f1e-4c7a-9b52-6f0d1a3c7e11 securitySchemes: bearerAuth: type: http scheme: bearer bearerFormat: iot_live_… ````