Go Kart Gear Ratio Calculator
Enter clutch and axle sprocket teeth, tyre size and engine RPM and get the gear ratio, theoretical top speed and a gear ratio chart, with jackshaft support.
Measure the tyre’s height when inflated. Works the same for mini bikes. The result updates as you type.
Gear ratio 5.00:1 · 3,600 RPM
Top speed ≈ 23.6 mph (37.9 km/h)
- Clutch 12T → axle 60T: 5.000:1
- Wheel speed 720 RPM · tyre circumference 34.56 in
A numerically lower ratio (fewer axle teeth or more clutch teeth) gives a higher top speed and slower acceleration; a higher ratio the opposite.
Gear ratio chart — top speed (mph) at 3,600 RPM
| Clutch \ Axle | 50T | 55T | 60T | 65T | 70T | 72T | 75T | 80T |
|---|---|---|---|---|---|---|---|---|
| 10T | 23.6 | 21.4 | 19.6 | 18.1 | 16.8 | 16.4 | 15.7 | 14.7 |
| 11T | 25.9 | 23.6 | 21.6 | 19.9 | 18.5 | 18.0 | 17.3 | 16.2 |
| 12T | 28.3 | 25.7 | 23.6 | 21.7 | 20.2 | 19.6 | 18.8 | 17.7 |
| 13T | 30.6 | 27.8 | 25.5 | 23.6 | 21.9 | 21.3 | 20.4 | 19.1 |
| 14T | 33.0 | 30.0 | 27.5 | 25.4 | 23.6 | 22.9 | 22.0 | 20.6 |
What this page cannot tell you
Whether the engine can actually pull that speed. The figure is theoretical: it assumes the engine reaches the RPM you entered and ignores wind, rolling resistance, tyre growth, slip and rider weight. A torque converter changes the ratio on the move, so this direct-drive figure does not apply to it.
How to work out a go-kart's gear ratio and top speed
- Count the teeth. On the clutch (engine) sprocket and the axle sprocket.
- Measure the drive tyre. Its height when inflated, in inches or centimetres.
- Enter the engine's top RPM. A governed small engine is often around 3,600 RPM; use your engine's figure.
- Read the result and chart. The ratio, theoretical top speed, and a chart of other sprocket combinations.
10 situations where a gear ratio calculator helps
Choosing an axle sprocket
See the top speed each sprocket size gives before buying one.
Making a kids' kart slower
A bigger axle sprocket raises the ratio and lowers top speed — see by how much.
Swapping to bigger tyres
Larger tyres raise top speed at the same ratio; the calculator shows the change.
Planning a jackshaft
Two stages multiply; enter both to get the overall ratio.
Gearing a mini bike
The same chain-drive arithmetic applies to mini bikes.
After raising engine RPM
Re-run the numbers when the engine's top RPM changes.
Comparing clutch sprockets
The chart lines up 10- to 14-tooth clutches against common axle sizes.
Checking a seller's speed claim
A listing's sprockets, tyres and RPM give a theoretical maximum.
Track days and racing classes
Find a ratio that suits a short, tight track versus a long straight.
Learning how gearing works
The breakdown shows wheel RPM and tyre circumference behind the number.
How the numbers are worked out
The method is the formula chain published with CSG Network's go-kart speed calculator, read on the date shown on the result: the tyre's circumference is π × diameter; the gear ratio is axle teeth ÷ clutch (engine) teeth; wheel RPM is engine RPM ÷ ratio; and speed is circumference × wheel RPM, converted from inches per minute to miles per hour (63,360 inches to a mile, 60 minutes to an hour). CSG's default — a 6-inch tyre, 3,600 RPM and a 60/12 ratio of 5 — gives 'just under 13 miles per hour'; this page gives 12.85 mph for the same inputs.
With a jackshaft, the drive has two stages: clutch to jackshaft, then jackshaft to axle. Their ratios multiply to give the overall ratio. The chart under the result applies your RPM and tyre size to direct-drive combinations of 10–14-tooth clutches and 50–80-tooth axle sprockets.
The arithmetic runs in your browser; nothing is stored or sent.
Limits: the speed is theoretical. It assumes the engine reaches the RPM entered at full speed, which it may not do against wind, rolling resistance and a heavy rider. Tyres also grow or squash at speed. Torque converters vary their ratio, so a fixed-ratio figure does not describe them. Nothing here is a statement about what speed is safe for a rider, a kart or a track.
Sources
- CSG Network — Go Kart Speed Calculator — Formula chain and worked default
Frequently asked questions
How do I calculate a go-kart gear ratio?
Divide the axle sprocket's teeth by the clutch sprocket's teeth. 60 axle teeth and 12 clutch teeth is 5:1.
What gear ratio gives the most top speed?
A numerically lower ratio — fewer axle teeth, or more clutch teeth — gives more top speed and less acceleration, as long as the engine can still reach its RPM.
How fast will a 212cc go-kart go?
It depends on gearing, tyres and RPM. At 3,600 RPM with 11-inch tyres and a 60/12 (5:1) ratio, the theoretical top speed is about 23.6 mph.
How do I calculate gear ratio with a jackshaft?
Work out each stage — jackshaft input ÷ clutch, then axle ÷ jackshaft output — and multiply them.
Why is my real top speed lower than the calculator?
The figure is theoretical: wind, rolling resistance, rider weight and the engine not reaching full RPM all take speed off.
Does this work for mini bikes?
Yes — any single-speed chain drive. Use the rear wheel's tyre diameter.
Does it work with a torque converter?
Not directly. A torque converter changes its ratio as speed rises, so a fixed-ratio calculation only gives an estimate at one ratio.
Related tools
Ski Size Chart
Enter height, and a child's weight, and get the suggested ski length range in cm from Nordica's adult and junior charts, plus which end of the range to lean toward.
Nordica Ski Sizer (adult and child charts)
Ski Boot Size Chart
Convert a Mondopoint ski boot size to US men's, women's, kids', EU and UK sizes, or the other way round, with Nordica's standard and performance fit sizes.
Nordica Ski Boot Sizing Chart (men's, women's and junior)
Snowboard Size Chart
Enter your weight and boot size and get the snowboard length from Jones's adult and kids charts, the middle size when you fall in two ranges, and the minimum waist width if you need a wide board.
Jones Snowboards size guide (weight charts and wide-board chart)
Scuba Weight Calculator
Enter your body weight, suit, water and tank and get a starting dive weight from PADI's and DAN's guidelines, with each adjustment listed.
PADI and DAN weighting guidelines; Scuba Diving magazine buoyancy article
What Year Is My Mercury Outboard?
Type the two-letter year code from your Mercury outboard's serial number decal and get the year it was made, using the table in Mercury's own manual.
Mercury Marine owner's manual 8M0165094, Model Year Production Code
Fishing Reel Line Capacity Calculator
Enter the reel's rated capacity and your line's diameter and get how many yards or metres of that line the spool holds, including braid over mono backing.
Spool capacity ∝ line diameter² × length (cylinder volume)