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What's this?

Our gear/speed ratio calculator tool lets you work out your road speed against engine speed.

This is a useful way of working out how a new gearset will compare to your existing one, as well as being an essential tool for race and rally teams to match a gearset to the terrains they will be tackling and their car's power band.

Shift speeds

Our tool can also work out your shift speeds and the rev drop on each shift if you tell it what RPM you change gear at. This is handy for fine-tuning your gearset, for example to hit 60 at the top of second gear, or to match your peak power band in a certain gear to a speed or range of speeds - invaluable if you are planning a 'box for a certain terrain.

Download instructions

To use this tool, you need an Excel compatible spreadsheet program on your PC.

Choose a version of the tool to download - the normal version is formatted for Microsoft Excel 2000-compatible programs, while the compatibility version is Microsoft Excel '95 and onwards compatible. Please check which version your spreadsheet program supports.

Right click on a link below and select "Save link". Please note that while we take every care to ensure our website content is safe, it's good practise to virus check the file before opening it.

How to use the tool

Once you have downloaded and opened the spreadsheet, fill in the details requested on the form.

Your tyre size: almost all tyres have a number on the wall which reads xxx/yyRzz. The width of the tyre, in mm, is the "xxx" part, e.g. 205.
Your sidewall size ratio: this is how high the tyre's sidewall as a percentage of the total width, and is the "yy" part of the tyre size, e.g. 50 means 50%.
Your rim diameter: this is the "zz" part of the tyre size, and is measured in inches.
Your gearset ratios: these are usually documented in your owner's handbook, or listed on this site for our own gearkits. If the ratio is "0.82:1", you need to type "0.82" into the spreadsheet.
Your shift RPM (optional): if you enter an engine speed to shift at, you can also find out what roadspeed each gearshift corresponds to, and your theoretical maximum speed in top gear.

Having problems?

If you can't get the spreadsheet to behave, or would just like more information about it, please send us an e-mail here.

Copyright and techie stuff

This tool is provided "as is": we have taken every step to ensure it will work on as many systems as possible, but we cannot guarantee it will work on your system. This spreadsheet is provided as-is with no warranty, express or implied. Full copyright remains with the author at all times.


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