Gear Ratio & Speed Calculator
Calculate vehicle speed from gear ratios, RPM, and tire size. Enter values for instant results with step-by-step formulas.
Worked Examples
Example 1: Highway Cruise
Problem:3000 RPM, 4th Gear (1.00), 3.73 Final, 26" Tire.
Solution:(3000 * 26) / (1.0 * 3.73 * 336) = 78000 / 1253.
Result:Speed: 62.2 MPH.
Frequently Asked Questions
How do I find my gear ratios?
Check your car's owner manual or search online for '[Car Model] transmission ratios'. Common codes: T56, 4L60E, ZF8.
How does tire size affect speed?
Larger tires cover more ground per rotation. They increase top speed (theoretically) but decrease acceleration.
What is a 1:1 gear?
Usually 4th or 5th gear. Input shaft speed equals Output shaft speed. Most efficient gear (no reduction loss).
Why do dynos use 1:1 gear?
To get the most accurate horsepower reading by minimizing transmission friction losses.