Gear Ratio & RPM Calculator
Swapping a final drive, regearing after bigger tires, or just curious what a transmission swap would cruise at? See engine RPM at any speed and your speed in every gear at redline.
Not sure of your tire diameter? Get it from the tire size calculator — it's the “overall diameter” figure.
| Gear | Ratio | Total (×FD) | RPM @ 70 mph | Speed @ redline |
|---|---|---|---|---|
| 1 | 3.27 | 13.41 | 12,318 | 39 mph |
| 2 | 2.13 | 8.73 | 8,023 | 59 mph |
| 3 | 1.52 | 6.23 | 5,726 | 83 mph |
| 4 | 1.15 | 4.71 | 4,332 | 110 mph |
| 5 | 0.92 | 3.77 | 3,466 | 137 mph |
| 6 | 0.74 | 3.03 | 2,787 | 171 mph |
Assumes no torque-converter slip and a 1:1 transfer case. RPM figures above your redline just mean that gear can't reach that speed.
How gear ratios and RPM relate
The classic formula is RPM = (speed × gear ratio × final drive × 336) ÷ tire diameter. The 336 folds the inches-per-mile and minutes-per-hour conversions into one constant. Multiply your gear ratio by the final drive to get the total reduction between crank and wheels.
This is why taller tires drop your cruising RPM (and make your speedometer read slow), and why trucks regear after fitting 35s — the bigger tire effectively raises every gear. It's also the quick way to sanity-check a final-drive swap: a 4.10 in place of a 3.73 raises RPM at every speed by about 10%, trading fuel economy for acceleration.
Planning a regear or transmission swap? Keep the spec sheet, parts list, and progress photos together in your Ryvve garage.
Frequently Asked Questions
Use RPM = (speed in mph × gear ratio × final drive ratio × 336) ÷ tire diameter in inches. The 336 constant folds the miles-to-inches and hours-to-minutes conversions together. This calculator applies that formula for every gear at once and also inverts it to show your top speed per gear at redline.
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