How to calculate gear ratios?

[Mapster1989]

I realise that some gear ratios are identical to others using different cogs but how is it calculated?

Reason why I ask is I have two bikes, one with an 8-speed triple and the other with a 10-speed double and I wanted to compare the two in terms of gear ratios.

Is there a simple calculation?

 

[Dave Davenport]

http://cycleseven.org/bicycle-gear-inch-calculator

 

[Mapster1989]

Thanks for that Dave.

 

[Rob500]

http://www.gear-calculator.com/#

I like this one. You can customize the amount of cogs and chainrings etc and show results as ratios, speed or development etc.

 

[Venod]

If you have excel on your computer, download the calculator from here.

http://www.tariksaleh.com/bike/gears.html

 

[Mapster1989]

http://www.gear-calculator.com/#

I like this one. You can customize the amount of cogs and chainrings etc and show results as ratios, speed or development etc.

Such an imaginative website name.