go kart plans

DIY Go Karts

Simplified Building Plans For Go Karts and Mini Bikes

How Fast is Your Go Kart?

Measuring Your Go Kart Speed and Calculating Gear Ratios

One of the most common questions we are asked is, "How fast will my kart go? What sprocket do I use?"

Go Kart Speed Calculator

To find your top speed, follow these easy steps:

1) Count the number of teeth on your clutch sprocket, and the number on the axle drive sprocket.

2) Find the top RPM your engine is rated for. If you're unsure, most are rated at 3600.

3) Measure the diameter of your rear tire. You can also measure from the ground to the center of the axle and multiply by 2.

Diameter in Inches Engine
on Axle
on Clutch
Diameter in Centimeters Engine
on Axle
on Clutch

How We Calculated Your Go Kart Speed

This is the formula for MPH:

Pi * tire diameter = circumfrence.

Circumfrence / 12 = circumfrence in feet.

Axle teeth / clutch teeth = gear ratio.

Engine RPMs / Gear Ratio = Wheel RPMS (wRPM)

Tire circumfrence in feet * wRPM = feet per minute.

Feet per minute * 60 = feet per hour.

Feet per hour / 5280 = miles per hour.

Go Kart Gear Ratio

The gear ratio on your mini bike or go kart is the ratio between the number of teeth on the clutch, and the number of teeth on the drive axle sprocket.

One of the most common gear ratios for go karts is 11-12 teeth on the clutch sprocket, and 60 teeth on the axle sprocket. A very common mini bike ratio is 11-12 teeth on the clutch, and 72 teeth on the axle sprocket.

To find the gear ratio, simply divide the axle teeth by the clutch teeth.

For example:

60 on the axle divided by 12 on the clutch = 5.


80 on the axle divided by 16 on the clutch also = 5.

Both of these sprocket combinations would result in the same performance on your kart!

As the gear ratio decreases, you can get a better top speed. However, you sacrifice power.

Think about how easy it is to start pedalling a mountain bike in 1st gear. That's a very high ratio, meaning the gear up front is small, and the gear in the back is big. So your feet (your engine!) can easily produce a lot of power for a hill, but you won't be able to go very fast.

How to Clock Your Actual Speed

Our calculator is useful, but it's just theoretical. To really know how fast you're going, we'll show you how to clock your speed using a stopwatch.

First, find a large, flat, open area so you can achieve maximum speed, such as aAn empty parking lot.

Make two marks in chalk as far apart as is safe. A longer distance is good because it ensures accuracy.

Using a stopwatch, start the timer when the driver crosses the first mark. When the cross the second mark, stop the watch.

Measure the distance between the two marks. Here is the formula:

Feet traveled / 5280 = miles traveled.

Seconds elapsed / 3600 = hours elapsed.

Miles / hours = MPH!