Gear ratio = ring gear teeth divided by pinion gear teeth. Enter tooth counts below for your axle ratio. Add tire diameter and engine RPM to see effective ratio and top speed at that RPM.
Optional: tire size and RPM for effective ratio and speed
Estimates only. Confirm with manufacturer specs.
Gear ratio = ring gear teeth / pinion gear teeth. A ring gear with 41 teeth meshed with an 11-tooth pinion produces a 3.73:1 ratio. The driveshaft turns 3.73 times for every one rotation of the axle shaft and wheel.
| Ratio | Best for | Highway RPM (typical) |
|---|---|---|
| 2.73:1 | Highway fuel economy, light duty | Low |
| 3.08:1 | General use, half-ton trucks | Moderate |
| 3.73:1 | Towing, moderate off-road | Moderate |
| 4.10:1 | Heavy towing, steep grades | Higher |
| 4.56:1 or higher | Competition, extreme off-road | High |
Every 10% increase in tire diameter lowers your effective gear ratio by roughly the same 10%. Going from 28-inch to 33-inch tires (an 18% increase) on a 4.10 axle gives you an effective ratio of about 3.38, which is closer to stock 3.08 territory. Many off-road builders re-gear after a tire lift to restore the original power feel.
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A gear ratio is the number of teeth on the ring gear divided by the number of teeth on the pinion gear. A 3.73:1 ratio means the driveshaft rotates 3.73 times for every one wheel rotation. Higher ratios give more torque; lower ratios give better highway fuel economy.
A ratio between 3.73:1 and 4.10:1 is common for towing because it provides more torque at low speeds. Anything above 4.56:1 is considered a high-performance or competition setup that trades fuel economy for pulling power.
Larger tires increase the effective gear ratio, which lowers your engine RPM at a given speed. If you go from a 28-inch tire to a 33-inch tire without re-gearing, your engine works less efficiently and acceleration suffers. The effective ratio adjusts for your tire diameter.
They are often the same number in practice, but final drive ratio can include additional gear reductions in the differential. In most street vehicles, the axle ratio stamped on the axle or listed in the owner's manual is the ring and pinion ratio.
Check the sticker on the door jamb, the owner's manual, or count the teeth on the ring and pinion gears directly. Many automakers also list the axle ratio in the VIN decoder or on the axle tag. This calculator lets you compute it directly from tooth counts.
A ratio that is too high (numerically large, such as 4.88) gives strong acceleration but high RPM at highway speed, reducing fuel economy. A ratio that is too low (numerically small, such as 2.73) cruises efficiently but feels sluggish off the line. Match the ratio to your primary use: towing, highway commuting, or performance driving.