Go-Kart Gear Ratio Calculator

Find the optimal sprocket combination for your go-kart. Calculate gear ratio, top speed at max RPM, and get recommended sprocket teeth for a target speed.

Inputs

Driver Sprocket Teeth

Axle Sprocket Teeth

Tire Circumference

Max Engine RPM

RPM

Target Top Speed

mph

Tab to move between fields

Results

Gear Ratio

6.5

Top Speed at Max RPM31.7 mph

RPM at Target Speed11,269 RPM

Recommended Driver Teeth16

Recommended Axle Teeth60

How to Use This Calculator

Enter Driver Sprocket Teeth, Axle Sprocket Teeth, and Tire Circumference.
Set Max Engine RPM and Target Top Speed.
Review the Gear Ratio result.
Use Top Speed at Max RPM (mph) and RPM at Target Speed to inform your decision.

How the result changes with Driver Sprocket Teeth

Driver Sprocket Teeth	Gear Ratio
7.9	8.23
13	5
18	3.61
23	2.83

What each input means

Driver Sprocket Teeth: Number of teeth on the engine (driver) sprocket. Smaller sprocket = more torque, less top speed.
Axle Sprocket Teeth: Number of teeth on the rear axle sprocket. Larger sprocket = more torque, less top speed.
Tire Circumference: Rear tire circumference in inches. Measure around the tire at the contact patch or calculate from diameter x pi.
Max Engine RPM: Maximum engine RPM (peak power RPM). Check your engine's spec sheet or tachometer.
Target Top Speed: Desired top speed in mph. The calculator will recommend sprocket sizes to achieve this.

What each result means

Gear Ratio: Current gear ratio (axle teeth / driver teeth). Higher = more torque.
Top Speed at Max RPM: Theoretical top speed with current sprocket combo at maximum engine RPM.
RPM at Target Speed: Engine RPM required to reach your target top speed with current gearing.
Recommended Driver Teeth: Suggested driver sprocket size to hit target speed at max RPM (range 8-20).
Recommended Axle Teeth: Suggested axle sprocket size to hit target speed at max RPM (range 50-90).

How this is calculated

Worked example, using the default values

Identify Input Parameters
4 parameters
Driver Sprocket Teeth = 10, Axle Sprocket Teeth = 65, Tire Circumference = 33.5, Max Engine RPM = 6500 = 5 input(s) provided
Calculate Gear Ratio
Gear Ratio
6.5 = 6.5
Calculate Top Speed at Max RPM
Top Speed at Max RPM
31.7 = 31.7
Calculate RPM at Target Speed
RPM at Target Speed
11269 = 11269

Engine last updated July 26, 2026. Checked against 1 independently-derived test — how we verify calculators.

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