If you have a geared bike count the number of sprockets in your rear cassette this will give you the speed of your chain.
Number of Sprockets.
Count how many full circles (sprockets) you have in your rear cassette. The common sizes are 6, 7, 8, 9, 10, 11, or 12 sprockets
If you have a 7 sprockets you need a 7 speed chain
If you have 11 sprockets you need an 11 speed chain