Bicycle gears

What gear am I in ? How can I compare my gears with another bike with a different wheel size, crankset and cassette ? Do I need an extra low gear for getting up steep hills ? My regular bike has 21 gears (3 at the front and 7 at the back) but does it really ? Actually there is a lot of overlapping of gear ratios.

'Gear inches' (Penny Farthing Gear) can be used to define absolute gear ratios on a bicycle. Follow these links for more information. Gear inches (wikipedia)    Bicycle gearing (wikipedia)

The other useful term when talking about gears is Cadence. In simple terms this is how fast your legs are turning the pedals in revolutions per minute (rpm). Follow this link for more information. Cadence (wikipedia)

The input fields below are filled as an example, overwrite with your own data then press one of the buttons below to create the results table.

Tip: keep a copy of the list of your sprocket teeth counts in a simple text file so you can paste them into the input fields.

Bicycle name:
Wheel diameter inches (including tyre):
Front crankset sprockets:
Rear casette sprockets:

The result table shows the gear ratios and speeds for each combination of sprockets and at different cadences. The default table sort is by sprockets, largest at the front and smallest at the rear. But the more interesting result is by gear ratios, so you can see just how much overlap there is in the sprocket combinations.

Show gears:    or