> ## 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. # Bolt Torque Calculator > Work out the tightening torque for a bolted joint using T = K·F·d. Pick a thread size (ISO metric coarse/fine or UNC) and a property class (8.8, 10.9, 12.9, A2-70, SAE 5/8) and the preload is derived from proof load automatically, or enter a target clamp load directly. Results in N·m, lbf·ft, lbf·in and kgf·m, with the resulting bolt stress. Runs entirely in your browser. [Try Bolt Torque Calculator in your browser →](https://iotools.cloud/tool/bolt-torque-calculator/) ## OpenAPI ````yaml https://api.iotools.cloud/v1/openapi post /v1/tool/bolt-torque-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/bolt-torque-calculator: post: tags: - Calculators summary: Bolt Torque Calculator description: >- Work out the tightening torque for a bolted joint using T = K·F·d. Pick a thread size (ISO metric coarse/fine or UNC) and a property class (8.8, 10.9, 12.9, A2-70, SAE 5/8) and the preload is derived from proof load automatically, or enter a target clamp load directly. Results in N·m, lbf·ft, lbf·in and kgf·m, with the resulting bolt stress. Runs entirely in your browser. [Try Bolt Torque Calculator in your browser →](https://iotools.cloud/tool/bolt-torque-calculator/) operationId: run_bolt_torque_calculator requestBody: required: false content: application/json: schema: type: object properties: mode: enum: - grade - preload description: Preload source thread: enum: - M3 - M4 - M5 - M6 - M8 - M8x1 - M10 - M10x1.25 - M12 - M12x1.25 - M14 - M16 - M16x1.5 - M18 - M20 - M20x1.5 - M22 - M24 - M27 - M30 - M33 - M36 - 1/4-20 - 5/16-18 - 3/8-16 - 1/2-13 - 5/8-11 - 3/4-10 - custom description: Thread size diameter: type: number description: Nominal diameter (mm) minimum: 0.5 maximum: 200 stressArea: type: number description: Tensile stress area Aₛ (mm²) minimum: 0.1 maximum: 40000 grade: enum: - '4.6' - '4.8' - '5.8' - '8.8' - '9.8' - '10.9' - '12.9' - A2-70 - A2-80 - SAE5 - SAE8 description: Bolt grade / property class preloadPercent: type: number description: Preload target (% of proof load) minimum: 25 maximum: 100 preload: type: number description: Target preload F (N) minimum: 1 maximum: 10000000 condition: enum: - '0.30' - '0.25' - '0.22' - '0.20' - '0.18' - '0.16' - '0.12' - '0.10' - custom description: Joint condition (nut factor K) nutFactor: type: number description: Nut factor K minimum: 0.01 maximum: 1 required: [] examples: m10_grade_8_8_lightly_oiled_65_of_proof_load: summary: M10 grade 8.8, lightly oiled, 65% of proof load value: mode: grade thread: M10 grade: '8.8' preloadPercent: '65' condition: '0.20' m16_grade_10_9_zinc_plated_75_of_proof_load: summary: M16 grade 10.9, zinc plated, 75% of proof load value: mode: grade thread: M16 grade: '10.9' preloadPercent: '75' condition: '0.22' known_preload_20_kn_on_a_12_mm_bolt_k_0_20: summary: 'Known preload: 20 kN on a 12 mm bolt, K = 0.20' value: mode: preload thread: M12 preload: '20000' condition: '0.20' 1_2_13_unc_sae_grade_8_anti_seize_70_of_proof_load: summary: 1/2"-13 UNC SAE Grade 8, anti-seize, 70% of proof load value: mode: grade thread: 1/2-13 grade: SAE8 preloadPercent: '70' condition: '0.10' responses: '200': description: Tool output content: application/json: examples: m10_grade_8_8_lightly_oiled_65_of_proof_load: summary: M10 grade 8.8, lightly oiled, 65% of proof load value: tool: bolt-torque-calculator tool_version: 1.0.1 outputs: torque: 43.73 N·m (32.26 lbf·ft) torqueTable: - unit: N·m value: '43.73' - unit: N·cm value: 4,373.2 - unit: kgf·m value: '4.459' - unit: lbf·ft value: '32.26' - unit: lbf·in value: '387.1' preloadUsed: 21,866 N (21.87 kN) — 65% of proof load boltStress: 377.0 MPa (65% of 580 MPa proof) notes: >- T = K · F · d = 0.20 × 21,866 N × 10 mm. K is an empirical constant that swallows thread and under-head friction — it varies with lubrication, coating, washer surface and reuse, so torque control alone typically scatters preload by ±25–30%. Do not substitute this estimate for torque-tension testing on a critical joint. credits_used: 3 credits_remaining: null m16_grade_10_9_zinc_plated_75_of_proof_load: summary: M16 grade 10.9, zinc plated, 75% of proof load value: tool: bolt-torque-calculator tool_version: 1.0.1 outputs: torque: 344.02 N·m (253.73 lbf·ft) torqueTable: - unit: N·m value: '344.02' - unit: N·cm value: 34,401.8 - unit: kgf·m value: '35.080' - unit: lbf·ft value: '253.73' - unit: lbf·in value: 3,044.8 preloadUsed: 97,733 N (97.73 kN) — 75% of proof load boltStress: 622.5 MPa (75% of 830 MPa proof) notes: >- T = K · F · d = 0.22 × 97,733 N × 16 mm. K is an empirical constant that swallows thread and under-head friction — it varies with lubrication, coating, washer surface and reuse, so torque control alone typically scatters preload by ±25–30%. Do not substitute this estimate for torque-tension testing on a critical joint. credits_used: 3 credits_remaining: null known_preload_20_kn_on_a_12_mm_bolt_k_0_20: summary: 'Known preload: 20 kN on a 12 mm bolt, K = 0.20' value: tool: bolt-torque-calculator tool_version: 1.0.1 outputs: torque: 48.00 N·m (35.40 lbf·ft) torqueTable: - unit: N·m value: '48.00' - unit: N·cm value: 4,800.0 - unit: kgf·m value: '4.895' - unit: lbf·ft value: '35.40' - unit: lbf·in value: '424.8' preloadUsed: 20,000 N (20.00 kN) boltStress: 237.2 MPa notes: >- Bolt stress at this preload is 237.2 MPa — check it against your bolt's proof strength (ISO 8.8 ≈ 580–600 MPa, 10.9 ≈ 830 MPa, 12.9 ≈ 970 MPa). T = K · F · d = 0.20 × 20,000 N × 12 mm. K is an empirical constant that swallows thread and under-head friction — it varies with lubrication, coating, washer surface and reuse, so torque control alone typically scatters preload by ±25–30%. Do not substitute this estimate for torque-tension testing on a critical joint. credits_used: 3 credits_remaining: null 1_2_13_unc_sae_grade_8_anti_seize_70_of_proof_load: summary: 1/2"-13 UNC SAE Grade 8, anti-seize, 70% of proof load value: tool: bolt-torque-calculator tool_version: 1.0.1 outputs: torque: 67.27 N·m (49.62 lbf·ft) torqueTable: - unit: N·m value: '67.27' - unit: N·cm value: 6,727.1 - unit: kgf·m value: '6.860' - unit: lbf·ft value: '49.62' - unit: lbf·in value: '595.4' preloadUsed: 52,969 N (52.97 kN) — 70% of proof load boltStress: 578.9 MPa (70% of 827 MPa proof) notes: >- Nut factors at or below 0.12 assume a genuinely effective coating or lubricant; verify with torque-tension testing before relying on them. T = K · F · d = 0.10 × 52,969 N × 12.7 mm. K is an empirical constant that swallows thread and under-head friction — it varies with lubrication, coating, washer surface and reuse, so torque control alone typically scatters preload by ±25–30%. Do not substitute this estimate for torque-tension testing on a critical joint. credits_used: 3 credits_remaining: null schema: type: object required: - tool - tool_version - outputs - credits_used - credits_remaining properties: outputs: type: object properties: torque: type: string description: Tightening torque torqueTable: type: array description: Torque in other units items: type: object properties: unit: type: string description: Unit value: type: string description: Value x-iotools-columns: - unit - value preloadUsed: type: string description: Preload (clamp load) boltStress: type: string description: Resulting bolt stress notes: type: string description: Notes & warnings 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_… ````