# Gear ratio speed calculator - Human page: https://happytails.ai/en/calculators/gear-ratio-speed-calculator/ - Markdown: https://happytails.ai/en/calculators/gear-ratio-speed-calculator.md - Structured JSON: https://happytails.ai/agents/en/calculators/gear-ratio-speed-calculator/index.json - Visibility: public ## Tool capabilities | Property | Value | | --- | --- | | Tool ID | `gear-ratio-speed-calculator` | | Category | calculators | | Implementation | Registered implementation. Registration alone is not a production-quality guarantee. | | Browser execution | Use the visible action or interactive controls. | | Browser processing | Browser; see tool notes for network behavior. | | HTTP API | Not callable through HTTP. | | Browser-agent interface | run_current_tool | ### Implementation notes Use measured rolling tire circumference from 100 to 10000 mm. Transmission and final-drive ratios are positive reductions, each at most 100. Engine speed accepts 0 to 100000 RPM; road-speed input accepts 0 to 2000 in the selected unit. Results assume a locked drivetrain without clutch, torque-converter or tire slip. They do not predict whether the engine has enough power to reach that speed. Do not use thousands separators. ### Inputs and settings No free-text input is required. Use the file inputs and/or settings below. | Setting | Meaning | Control type | Default | Constraints | | --- | --- | --- | --- | --- | | `direction` | Calculate | select | "rpm-to-speed" | Allowed: rpm-to-speed, speed-to-rpm | | `engineRpm` | Engine speed (RPM) | text | "3000" | | | `speed` | Road speed | text | "45" | | | `speedUnit` | Speed unit | select | "km/h" | Allowed: km/h, mph | | `transmissionRatio` | Transmission reduction ratio | text | "2" | | | `finalDriveRatio` | Final-drive reduction ratio | text | "4" | | | `circumferenceMm` | Rolling tire circumference (mm) | text | "2000" | | ### Browser-agent workflow 1. Open the human page in a browser that supports WebMCP. 2. Discover the interface exposed by that page; use its actual schema. 3. Select files on the page first when the tool requires files. 4. Call `run_current_tool` with valid input and settings. 5. Inspect the returned result or error and the displayed output. Retrieve files from the displayed download links. Calls do not automatically copy or download results. Browser permissions still apply. Interface availability alone is not proof of successful execution. ### Planning specification Use positive transmission and final-drive ratios up to 100, circumference from 100 to 10000 mm, engine-speed input from 0 to 100000 RPM and speed input from 0 to 2000 in the selected unit. Decimal inputs allow up to six places. These are software bounds, not vehicle capability claims. Results use floating-point arithmetic. Processing stays on your device, with a bounded worker and a 10-second timeout. Full JSON and CSV preserve every calculated row and the assumptions. Do not use thousands separators. This describes intended requirements. Use the implementation notes, interface schema and observed output to determine current support. ### Complete machine-readable capability record ```json { "id": "gear-ratio-speed-calculator", "category": "calculators", "built": true, "requirements": "Use positive transmission and final-drive ratios up to 100, circumference from 100 to 10000 mm, engine-speed input from 0 to 100000 RPM and speed input from 0 to 2000 in the selected unit. Decimal inputs allow up to six places. These are software bounds, not vehicle capability claims. Results use floating-point arithmetic. Processing stays on your device, with a bounded worker and a 10-second timeout. Full JSON and CSV preserve every calculated row and the assumptions. Do not use thousands separators.", "implementation": { "fields": [ { "key": "direction", "label": "Calculate", "value": "rpm-to-speed", "type": "select", "values": [ "rpm-to-speed", "speed-to-rpm" ], "labels": { "rpm-to-speed": "Speed from RPM", "speed-to-rpm": "RPM from speed" } }, { "key": "engineRpm", "label": "Engine speed (RPM)", "value": "3000", "type": "text", "inputMode": "decimal", "maxLength": 24, "showWhen": { "direction": [ "rpm-to-speed" ] } }, { "key": "speed", "label": "Road speed", "value": "45", "type": "text", "inputMode": "decimal", "maxLength": 24, "showWhen": { "direction": [ "speed-to-rpm" ] } }, { "key": "speedUnit", "label": "Speed unit", "value": "km/h", "type": "select", "values": [ "km/h", "mph" ], "labels": { "km/h": "Kilometers per hour", "mph": "Miles per hour" }, "showWhen": { "direction": [ "speed-to-rpm" ] } }, { "key": "transmissionRatio", "label": "Transmission reduction ratio", "value": "2", "type": "text", "inputMode": "decimal", "maxLength": 24 }, { "key": "finalDriveRatio", "label": "Final-drive reduction ratio", "value": "4", "type": "text", "inputMode": "decimal", "maxLength": 24 }, { "key": "circumferenceMm", "label": "Rolling tire circumference (mm)", "value": "2000", "type": "text", "inputMode": "decimal", "maxLength": 24 } ], "input": false, "presentation": "metrics", "note": "Use measured rolling tire circumference from 100 to 10000 mm. Transmission and final-drive ratios are positive reductions, each at most 100. Engine speed accepts 0 to 100000 RPM; road-speed input accepts 0 to 2000 in the selected unit. Results assume a locked drivetrain without clutch, torque-converter or tire slip. They do not predict whether the engine has enough power to reach that speed. Do not use thousands separators.", "experience": { "automatic": false, "single": false, "inputMaxLength": 1000000, "inputMode": "text", "label": "Your text", "placeholder": "Type or paste your input…", "help": "Up to 1,000,000 characters. Review the settings before running.", "action": null }, "mode": "explicit", "interactive": false }, "execution": "Browser interface", "api": null, "browser_agent": { "supported": true, "name": "run_current_tool", "discovery": "WebMCP on the human page in a supporting browser", "verification": "See audit/API-AUDIT.md; availability is not verification" } } ``` ## Page guide Calculate road speed from engine RPM and gearing, or engine RPM from road speed. How can we improve this tool? Report a problem or share an idea. Please leave out private information. Your message and the tool name go to our team via PostHog. ### How to use Gear ratio speed calculator 1. Choose whether to calculate road speed or engine RPM. 2. Enter the transmission and final-drive reduction ratios and rolling tire circumference. 3. Enter the selected speed input, calculate and download the full report. ## Useful next steps - [Bicycle gear calculator](https://happytails.ai/en/calculators/bicycle-gear-calculator/) ([Markdown](https://happytails.ai/en/calculators/bicycle-gear-calculator.md)) - [Cycling cadence calculator](https://happytails.ai/en/calculators/cycling-cadence-calculator/) ([Markdown](https://happytails.ai/en/calculators/cycling-cadence-calculator.md)) ## Follow the complete reduction Overall reduction is transmission ratio multiplied by final-drive ratio. Wheel RPM is engine RPM divided by overall reduction. Multiplying wheel RPM by rolling circumference and dividing by 60 gives road speed in meters per second. ### Calculate in either direction For engine RPM from road speed, reverse the same formula. Use reduction ratios as input, rather than their reciprocals. The model assumes a locked drivetrain and does not simulate torque-converter slip, clutch slip, tire slip, engine power or road resistance.