CHAIN INCHES CHART

Knowing your chain inches is useful for determining if a particular gear ratio is bigger or smaller than another, or if they are redundant. Track riders especially need to know this. For instance, a 47x14 is actually a bigger gear than a 49x15.

Chain inches = front chainring teeth / rear cog teeth x wheel diameter (in inches)

This chart was stolen from bikehighway.com.

 

Chainring
Cog 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53
11 94.0 96.4 98.8 101.2 103.6 106.0 108.4 110.8 115.4 117.8 120.3 122.7 125.2 127.6 130.1
12 86.1 88.3 90.5 92.8 95.0 97.2 99.4 101.6 105.8 108 110.2 112.5 114.8 117 119.3
13 79.5 81.5 83.6 85.6 87.7 89.7 91.7 93.8 97.6 99.7 101.8 103.8 105.9 108 110.1
14 73.8 75.7 77.6 79.5 81.4 83.3 85.2 87.1 90.6 92.6 94.5 96.4 98.4 100.3 102.2
15 68.9 70.7 72.4 74.2 76.0 77.7 79.5 81.3 84.6 86.4 88.2 90 91.8 93.6 95.4
16 64.6 66.3 67.9 69.6 71.2 72.9 74.5 76.2 79.3 81 82.7 84.4 86.1 87.8 89.4
17 60.8 62.4 63.9 65.5 67.0 68.6 70.1 71.7 74.6 76.2 77.8 79.4 81 82.6 84.2
18 57.4 58.9 60.4 61.8 63.3 64.8 66.3 67.7 70.5 72 73.5 75 76.5 78 79.5
19 54.4 55.8 57.2 58.6 60.0 61.4 62.8 64.2 66.8 68.2 69.6 71.1 72.5 73.9 75.3
20 51.7 53.0 54.3 55.7 57.0 58.3 59.6 61.0 63.5 64.8 66.2 67.5 68.8 70.2 71.5
21 49.2 50.5 51.7 53.0 54.3 55.5 56.8 58.0 60.4 61.7 63 64.3 65.6 66.9 68.1
22 47.0 48.2 49.4 50.6 51.8 53.0 54.2 55.4 57.7 58.9 60.1 61.4 62.6 63.8 65
23 44.9 46.1 47.2 48.4 49.5 50.7 51.8 53.0 55.2 56.3 57.5 58.7 59.9 61 62.2
24 43.1 44.2 45.3 46.4 47.5 48.6 49.7 50.8 52.9 54 55.1 56.3 57.4 58.5 59.6
25 41.3 42.4 43.5 44.5 45.6 46.6 47.7 48.8 50.8 51.8 52.9 54 55.1 56.2 57.2
Cog 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53
 

Chainring