The Gear Ratio Calculator is a free tool that helps you calculate gear ratio using the formula Ratio = driven / driving; output rpm = input x driving / driven. Enter your values above and press Calculate to get gear ratio, output speed instantly, with a full step-by-step breakdown.
What is the Gear Ratio Calculator?
The gear ratio calculator is a free online tool that helps you calculate gear ratio quickly and accurately. It applies the standard formula Ratio = driven / driving; output rpm = input x driving / driven to the values you enter and, when you press Calculate, displays the result together with a clear, step-by-step explanation of how the answer was reached.
How to use the Gear Ratio Calculator
- Enter teeth on the driving and driven gears.
- Optionally enter input rpm.
- See the gear ratio.
Formula used
The gear ratio calculator is based on this formula:
Ratio = driven / driving; output rpm = input x driving / drivenEach term in the formula corresponds to one of the inputs explained below. The calculator performs the arithmetic for you and shows every step so you can check the working by hand if you wish.
Worked example
Suppose you enter 12 and 36 teeth. The calculator works as follows:
| Inputs | 12 and 36 teeth |
|---|---|
| Working | 36/12 |
| Result | 3:1, output 333 rpm |
Step-by-step calculation
- Apply the formula:
Ratio = driven / driving; output rpm = input x driving / driven - Substitute your values: 36/12
- Read the result: 3:1, output 333 rpm
Inputs explained
- Driving gear teeth โ the driving gear teeth used in the calculation.
- Driven gear teeth โ the driven gear teeth used in the calculation.
- Input speed (rpm) โ the input speed used in the calculation.
Understanding your result
- Gear ratio โ the calculated gear ratio.
- Output speed โ the calculated output speed in rpm.
Benefits and practical uses
The gear ratio calculator saves time and removes the risk of manual errors when you need to calculate gear ratio. It is useful for students, professionals and anyone who wants a fast, dependable answer. Results update the moment you press Calculate, work on any device, and can be copied or shared in a single click โ and because the maths runs in your browser, your figures stay completely private.
Tips for an accurate result
- Keep all related inputs in the same units.
- Use the worked example above to confirm you are entering values in the right places.
- Review the assumptions below so the result fits your situation.
- Press Reset to clear everything and try a different scenario.
Common mistakes to avoid
- Entering values in the wrong unit (mismatched units give wrong answers).
- Leaving a required field empty โ the calculator will ask you to fill it in.
- Rounding inputs too early, which can slightly change the result.
Assumptions and limitations
- Ideal gear mesh, no losses.
Frequently asked questions
What does a 3:1 ratio mean?
The driving gear turns three times for each turn of the driven gear, trading speed for torque.
How do I use the Gear Ratio Calculator?
Enter your values in the fields, then press the Calculate button to see the result. Use Reset to clear the form and start again. Nothing is calculated until you click Calculate.
What formula does the Gear Ratio Calculator use?
It uses the standard formula: Ratio = driven / driving; output rpm = input x driving / driven. The full step-by-step working is shown with every result so you can verify it.
What information do I need to use the gear ratio calculator?
You need: driving gear teeth, driven gear teeth, input speed. Sensible example values are pre-filled so you can see how it works.
Is the Gear Ratio Calculator free to use?
Yes. Every DigiToolkit calculator is completely free, with no sign-up, no login and no usage limits.
Does the Gear Ratio Calculator work on mobile phones?
Yes. The calculator is mobile-first and works on phones, tablets and computers in any modern browser.
Do I need to install an app?
No. The gear ratio calculator runs directly in your web browser โ there is nothing to download or install.
Is my data private when I use this calculator?
Yes. All calculations run inside your browser. The numbers you enter are never uploaded to a server or shared with anyone.
How accurate is the Gear Ratio Calculator?
It uses the generally accepted formula for gear ratio and computes to several decimal places. Results are accurate for the assumptions listed on this page.
Can I copy or share my result?
Yes. After calculating, use the Copy button to copy the result, or Share to copy the page link.
Why is nothing showing until I press Calculate?
By design, the calculator only computes when you press Calculate, so you can finish entering all your values first. Press Reset any time to clear everything.
What units does the Gear Ratio Calculator use?
It works with rpm. Keep your inputs in consistent units for an accurate result.