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gear inch charts
 

gear inch calculations

 

Gear Inches are used to give a numberical value to how a particular chainwheel/cog combination will feel. Classic BMX gearing evolved over the years to be 44/16,which has 55 gear inches. The most popular gear ratios are pretty close to a 55 inch, which just seems to feel best for most people. In the charts below, I've bolded the most common combo's. The number is derived from a simple formula: (chainring size divided by cog size) multiplied by wheel size.

If you want to learn more about gear ratios, go read the late, great Sheldon Brown's explanation here.

 

BMX 20 inch Gear Inch Chart

 

cog size
8
9
10
11
12
13
14
15
16
17
18
 
23
57.5
51.1
46.0
41.8
38.3
35.4
32.9
30.7
28.8
27.1
25.6
 
24
60.0
53.3
48.0
43.6
40.0
36.9
34.3
32.0
30.0
28.2
26.7
 
25
62.5
55.6
50.0
45.5
41.7
38.5
35.7
33.3
31.3
29.4
27.8
 
26
65.0
57.8
52.0
47.3
43.3
40.0
37.1
34.7
32.5
30.6
28.9
 
27
67.5
60.0
54.0
49.1
45.0
41.5
38.6
36.0
33.8
31.8
30.0
 
28
70.0
62.2
56.0
50.9
46.7
43.1
40.0
37.3
35.0
32.9
31.1
 
29
72.5
64.4
58.0
52.7
48.3
44.6
41.4
38.7
36.3
34.1
32.2
 
30
75.0
66.7
60.0
54.5
50.0
46.2
42.9
40.0
37.5
35.3
33.3
 
31
77.5
68.9
62.0
56.4
51.7
47.7
44.3
41.3
38.8
36.5
34.4
32
80.0
71.1
64.0
58.2
53.3
49.2
45.7
42.7
40.0
37.6
35.6
33
82.5
73.3
66.0
60.0
55.0
50.8
47.1
44.0
41.3
38.8
36.7
34
85.0
75.6
68.0
61.8
56.7
52.3
48.6
45.3
42.5
40.0
37.8
35
87.5
77.8
70.0
63.6
58.3
53.8
50.0
46.7
43.8
41.2
38.9
36
90.0
80.0
72.0
65.5
60.0
55.4
51.4
48.0
45.0
42.4
40.0
37
92.5
82.2
74.0
67.3
61.7
56.9
52.9
49.3
46.3
43.5
41.1
38
95.0
84.4
76.0
69.1
63.3
58.5
54.3
50.7
47.5
44.7
42.2
 
39
97.5
86.7
78.0
70.9
65.0
60.0
55.7
52.0
48.8
45.9
43.3
 
40
100.0
88.9
80.0
72.7
66.7
61.5
57.1
53.3
50.0
47.1
44.4
 
41
102.5
91.1
82.0
74.5
68.3
63.1
58.6
54.7
51.3
48.2
45.6
 
42
105.0
93.3
84.0
76.4
70.0
64.6
60.0
56.0
52.5
49.4
46.7
 
43
107.5
95.6
86.0
78.2
71.7
66.2
61.4
57.3
53.8
50.6
47.8
 
44
110.0
97.8
88.0
80.0
73.3
67.7
62.9
58.7
55.0
51.8
48.9
 
45
112.5
100.0
90.0
81.8
75.0
69.2
64.3
60.0
56.3
52.9
50.0
 
46
115.0
102.2
92.0
83.6
76.7
70.8
65.7
61.3
57.5
54.1
51.1
 
47
117.5
104.4
94.0
85.5
78.3
72.3
67.1
62.7
58.8
55.3
52.2
 
48
120.0
106.7
96.0
87.3
80.0
73.8
68.6
64.0
60.0
56.5
53.3
 
49
122.5
108.9
98.0
89.1
81.7
75.4
70.0
65.3
61.3
57.6
54.4

 

 

bmx 20 x 1 1/8 and 20 x 1 3/8 gear chart

 

       
cog size
       
8
9
10
11
12
13
14
15
16
17
18
 
23
60.4
53.7
48.3
43.9
40.3
37.2
34.5
32.2
30.2
28.4
26.8
 
24
63.0
56.0
50.4
45.8
42.0
38.8
36.0
33.6
31.5
29.6
28.0
 
25
65.6
58.3
52.5
47.7
43.8
40.4
37.5
35.0
32.8
30.9
29.2
 
26
68.3
60.7
54.6
49.6
45.5
42.0
39.0
36.4
34.1
32.1
30.3
 
27
70.9
63.0
56.7
51.5
47.3
43.6
40.5
37.8
35.4
33.4
31.5
 
28
73.5
65.3
58.8
53.5
49.0
45.2
42.0
39.2
36.8
34.6
32.7
 
29
76.1
67.7
60.9
55.4
50.8
46.8
43.5
40.6
38.1
35.8
33.8
 
30
78.8
70.0
63.0
57.3
52.5
48.5
45.0
42.0
39.4
37.1
35.0
 
31
81.4
72.3
65.1
59.2
54.3
50.1
46.5
43.4
40.7
38.3
36.2
32
84.0
74.7
67.2
61.1
56.0
51.7
48.0
44.8
42.0
39.5
37.3
33
86.6
77.0
69.3
63.0
57.8
53.3
49.5
46.2
43.3
40.8
38.5
34
89.3
79.3
71.4
64.9
59.5
54.9
51.0
47.6
44.6
42.0
39.7
35
91.9
81.7
73.5
66.8
61.3
56.5
52.5
49.0
45.9
43.2
40.8
36
94.5
84.0
75.6
68.7
63.0
58.2
54.0
50.4
47.3
44.5
42.0
37
97.1
86.3
77.7
70.6
64.8
59.8
55.5
51.8
48.6
45.7
43.2
38
99.8
88.7
79.8
72.5
66.5
61.4
57.0
53.2
49.9
46.9
44.3
 
39
102.4
91.0
81.9
74.5
68.3
63.0
58.5
54.6
51.2
48.2
45.5
 
40
105.0
93.3
84.0
76.4
70.0
64.6
60.0
56.0
52.5
49.4
46.7
 
41
107.6
95.7
86.1
78.3
71.8
66.2
61.5
57.4
53.8
50.6
47.8
 
42
110.3
98.0
88.2
80.2
73.5
67.8
63.0
58.8
55.1
51.9
49.0
 
43
112.9
100.3
90.3
82.1
75.3
69.5
64.5
60.2
56.4
53.1
50.2
 
44
115.5
102.7
92.4
84.0
77.0
71.1
66.0
61.6
57.8
54.4
51.3
 
45
118.1
105.0
94.5
85.9
78.8
72.7
67.5
63.0
59.1
55.6
52.5
 
46
120.8
107.3
96.6
87.8
80.5
74.3
69.0
64.4
60.4
56.8
53.7
 
47
123.4
109.7
98.7
89.7
82.3
75.9
70.5
65.8
61.7
58.1
54.8
 
48
126.0
112.0
100.8
91.6
84.0
77.5
72.0
67.2
63.0
59.3
56.0
 
49
128.6
114.3
102.9
93.5
85.8
79.2
73.5
68.6
64.3
60.5
57.2

 

 

 

bmx 24 inch gear chart

 
cog size
 
8
9
10
11
12
13
14
15
16
17
18
 
23
69.0
61.3
55.2
50.2
46.0
42.5
39.4
36.8
34.5
32.5
30.7
 
24
72.0
64.0
57.6
52.4
48.0
44.3
41.1
38.4
36.0
33.9
32.0
 
25
75.0
66.7
60.0
54.5
50.0
46.2
42.9
40.0
37.5
35.3
33.3
 
26
78.0
69.3
62.4
56.7
52.0
48.0
44.6
41.6
39.0
36.7
34.7
 
27
81.0
72.0
64.8
58.9
54.0
49.8
46.3
43.2
40.5
38.1
36.0
 
28
84.0
74.7
67.2
61.1
56.0
51.7
48.0
44.8
42.0
39.5
37.3
 
29
87.0
77.3
69.6
63.3
58.0
53.5
49.7
46.4
43.5
40.9
38.7
 
30
90.0
80.0
72.0
65.5
60.0
55.4
51.4
48.0
45.0
42.4
40.0
 
31
93.0
82.7
74.4
67.6
62.0
57.2
53.1
49.6
46.5
43.8
41.3
32
96.0
85.3
76.8
69.8
64.0
59.1
54.9
51.2
48.0
45.2
42.7
33
99.0
88.0
79.2
72.0
66.0
60.9
56.6
52.8
49.5
46.6
44.0
34
102.0
90.7
81.6
74.2
68.0
62.8
58.3
54.4
51.0
48.0
45.3
35
105.0
93.3
84.0
76.4
70.0
64.6
60.0
56.0
52.5
49.4
46.7
36
108.0
96.0
86.4
78.5
72.0
66.5
61.7
57.6
54.0
50.8
48.0
37
111.0
98.7
88.8
80.7
74.0
68.3
63.4
59.2
55.5
52.2
49.3
38
114.0
101.3
91.2
82.9
76.0
70.2
65.1
60.8
57.0
53.6
50.7
 
39
117.0
104.0
93.6
85.1
78.0
72.0
66.9
62.4
58.5
55.1
52.0
 
40
120.0
106.7
96.0
87.3
80.0
73.8
68.6
64.0
60.0
56.5
53.3
 
41
123.0
109.3
98.4
89.5
82.0
75.7
70.3
65.6
61.5
57.9
54.7
 
42
126.0
112.0
100.8
91.6
84.0
77.5
72.0
67.2
63.0
59.3
56.0
 
43
129.0
114.7
103.2
93.8
86.0
79.4
73.7
68.8
64.5
60.7
57.3
 
44
132.0
117.3
105.6
96.0
88.0
81.2
75.4
70.4
66.0
62.1
58.7
 
45
135.0
120.0
108.0
98.2
90.0
83.1
77.1
72.0
67.5
63.5
60.0
 
46
138.0
122.7
110.4
100.4
92.0
84.9
78.9
73.6
69.0
64.9
61.3
 
47
141.0
125.3
112.8
102.5
94.0
86.8
80.6
75.2
70.5
66.4
62.7
 
48
144.0
128.0
115.2
104.7
96.0
88.6
82.3
76.8
72.0
67.8
64.0
 
49
147.0
130.7
117.6
106.9
98.0
90.5
84.0
78.4
73.5
69.2
65.3

 

 

mtb 26 inch gear chart

 

         
cog size
           
8
9
10
11
12
13
14
15
16
17
18
19
20
21
23
74.8
66.4
59.8
54.4
49.8
46.0
42.7
39.9
37.4
35.2
33.2
31.5
29.9
28.5
24
78.0
69.3
62.4
56.7
52.0
48.0
44.6
41.6
39.0
36.7
34.7
32.8
31.2
29.7
25
81.3
72.2
65.0
59.1
54.2
50.0
46.4
43.3
40.6
38.2
36.1
34.2
32.5
31.0
26
84.5
75.1
67.6
61.5
56.3
52.0
48.3
45.1
42.3
39.8
37.6
35.6
33.8
32.2
27
87.8
78.0
70.2
63.8
58.5
54.0
50.1
46.8
43.9
41.3
39.0
36.9
35.1
33.4
28
91.0
80.9
72.8
66.2
60.7
56.0
52.0
48.5
45.5
42.8
40.4
38.3
36.4
34.7
29
94.3
83.8
75.4
68.5
62.8
58.0
53.9
50.3
47.1
44.4
41.9
39.7
37.7
35.9
30
97.5
86.7
78.0
70.9
65.0
60.0
55.7
52.0
48.8
45.9
43.3
41.1
39.0
37.1
31
100.8
89.6
80.6
73.3
67.2
62.0
57.6
53.7
50.4
47.4
44.8
42.4
40.3
38.4
32
104.0
92.4
83.2
75.6
69.3
64.0
59.4
55.5
52.0
48.9
46.2
43.8
41.6
39.6
33
107.3
95.3
85.8
78.0
71.5
66.0
61.3
57.2
53.6
50.5
47.7
45.2
42.9
40.9
34
110.5
98.2
88.4
80.4
73.7
68.0
63.1
58.9
55.3
52.0
49.1
46.5
44.2
42.1
35
113.8
101.1
91.0
82.7
75.8
70.0
65.0
60.7
56.9
53.5
50.6
47.9
45.5
43.3
36
117.0
104.0
93.6
85.1
78.0
72.0
66.9
62.4
58.5
55.1
52.0
49.3
46.8
44.6
37
120.3
106.9
96.2
87.5
80.2
74.0
68.7
64.1
60.1
56.6
53.4
50.6
48.1
45.8
38
123.5
109.8
98.8
89.8
82.3
76.0
70.6
65.9
61.8
58.1
54.9
52.0
49.4
47.0
39
126.8
112.7
101.4
92.2
84.5
78.0
72.4
67.6
63.4
59.6
56.3
53.4
50.7
48.3
40
130.0
115.6
104.0
94.5
86.7
80.0
74.3
69.3
65.0
61.2
57.8
54.7
52.0
49.5
41
133.3
118.4
106.6
96.9
88.8
82.0
76.1
71.1
66.6
62.7
59.2
56.1
53.3
50.8
42
136.5
121.3
109.2
99.3
91.0
84.0
78.0
72.8
68.3
64.2
60.7
57.5
54.6
52.0
43
139.8
124.2
111.8
101.6
93.2
86.0
79.9
74.5
69.9
65.8
62.1
58.8
55.9
53.2
44
143.0
127.1
114.4
104.0
95.3
88.0
81.7
76.3
71.5
67.3
63.6
60.2
57.2
54.5
45
146.3
130.0
117.0
106.4
97.5
90.0
83.6
78.0
73.1
68.8
65.0
61.6
58.5
55.7
46
149.5
132.9
119.6
108.7
99.7
92.0
85.4
79.7
74.8
70.4
66.4
62.9
59.8
57.0
47
152.8
135.8
122.2
111.1
101.8
94.0
87.3
81.5
76.4
71.9
67.9
64.3
61.1
58.2
48
156.0
138.7
124.8
113.5
104.0
96.0
89.1
83.2
78.0
73.4
69.3
65.7
62.4
59.4
49
159.3
141.6
127.4
115.8
106.2
98.0
91.0
84.9
79.6
74.9
70.8
67.1
63.7
60.7

 

 

fixed gear 27 inch gear chart

 

     
cog size
     
12
13
14
15
16
17
18
19
20
 
23
51.8
47.8
44.4
41.4
38.8
36.5
34.5
32.7
31.1
 
24
54.0
49.8
46.3
43.2
40.5
38.1
36.0
34.1
32.4
 
25
56.3
51.9
48.2
45.0
42.2
39.7
37.5
35.5
33.8
 
26
58.5
54.0
50.1
46.8
43.9
41.3
39.0
36.9
35.1
 
27
60.8
56.1
52.1
48.6
45.6
42.9
40.5
38.4
36.5
 
28
63.0
58.2
54.0
50.4
47.3
44.5
42.0
39.8
37.8
 
29
65.3
60.2
55.9
52.2
48.9
46.1
43.5
41.2
39.2
 
30
67.5
62.3
57.9
54.0
50.6
47.6
45.0
42.6
40.5
 
31
69.8
64.4
59.8
55.8
52.3
49.2
46.5
44.1
41.9
 
32
72.0
66.5
61.7
57.6
54.0
50.8
48.0
45.5
43.2
 
33
74.3
68.5
63.6
59.4
55.7
52.4
49.5
46.9
44.6
 
34
76.5
70.6
65.6
61.2
57.4
54.0
51.0
48.3
45.9
35
78.8
72.7
67.5
63.0
59.1
55.6
52.5
49.7
47.3
36
81.0
74.8
69.4
64.8
60.8
57.2
54.0
51.2
48.6
37
83.3
76.8
71.4
66.6
62.4
58.8
55.5
52.6
50.0
38
85.5
78.9
73.3
68.4
64.1
60.4
57.0
54.0
51.3
39
87.8
81.0
75.2
70.2
65.8
61.9
58.5
55.4
52.7
40
90.0
83.1
77.1
72.0
67.5
63.5
60.0
56.8
54.0
41
92.3
85.2
79.1
73.8
69.2
65.1
61.5
58.3
55.4
 
42
94.5
87.2
81.0
75.6
70.9
66.7
63.0
59.7
56.7
 
43
96.8
89.3
82.9
77.4
72.6
68.3
64.5
61.1
58.1
 
44
99.0
91.4
84.9
79.2
74.3
69.9
66.0
62.5
59.4
 
45
101.3
93.5
86.8
81.0
75.9
71.5
67.5
63.9
60.8
 
46
103.5
95.5
88.7
82.8
77.6
73.1
69.0
65.4
62.1
 
47
105.8
97.6
90.6
84.6
79.3
74.6
70.5
66.8
63.5
 
48
108.0
99.7
92.6
86.4
81.0
76.2
72.0
68.2
64.8
 
49
110.3
101.8
94.5
88.2
82.7
77.8
73.5
69.6
66.2
 
50
112.5
103.8
96.4
90.0
84.4
79.4
75.0
71.1
67.5
 
51
114.8
105.9
98.4
91.8
86.1
81.0
76.5
72.5
68.9
 
52
117.0
108.0
100.3
93.6
87.8
82.6
78.0
73.9
70.2
 
53
119.3
110.1
102.2
95.4
89.4
84.2
79.5
75.3
71.6
 
54
121.5
112.2
104.1
97.2
91.1
85.8
81.0
76.7
72.9

 

 

mtb 29 inch gear chart

 

         
cog size
           
8
9
10
11
12
13
14
15
16
17
18
19
20
21
23
83.4
74.1
66.7
60.6
55.6
51.3
47.6
44.5
41.7
39.2
37.1
35.1
33.4
31.8
24
87.0
77.3
69.6
63.3
58.0
53.5
49.7
46.4
43.5
40.9
38.7
36.6
34.8
29.7
25
90.6
80.6
72.5
65.9
60.4
55.8
51.8
48.3
45.3
42.6
40.3
38.2
36.3
31.0
26
94.3
83.8
75.4
68.5
62.8
58.0
53.9
50.3
47.1
44.4
41.9
39.7
37.7
32.2
27
97.9
87.0
78.3
71.2
65.3
60.2
55.9
52.2
48.9
46.1
43.5
41.2
39.2
33.4
28
101.5
90.2
81.2
73.8
67.7
62.5
58.0
54.1
50.8
47.8
45.1
42.7
40.6
34.7
29
105.1
93.4
84.1
76.5
70.1
64.7
60.1
56.1
52.6
49.5
46.7
44.3
42.1
35.9
30
108.8
96.7
87.0
79.1
72.5
66.9
62.1
58.0
54.4
51.2
48.3
45.8
43.5
37.1
31
112.4
99.9
89.9
81.7
74.9
69.2
64.2
59.9
56.2
52.9
49.9
47.3
45.0
38.4
32
116.0
103.1
92.8
84.4
77.3
71.4
66.3
61.9
58.0
54.6
51.6
48.8
46.4
39.6
33
119.6
106.3
95.7
87.0
79.8
73.6
68.4
63.8
59.8
56.3
53.2
50.4
47.9
40.9
34
123.3
109.6
98.6
89.6
82.2
75.8
70.4
65.7
61.6
58.0
54.8
51.9
49.3
42.1
35
126.9
112.8
101.5
92.3
84.6
78.1
72.5
67.7
63.4
59.7
56.4
53.4
50.8
43.3
36
130.5
116.0
104.4
94.9
87.0
80.3
74.6
69.6
65.3
61.4
58.0
54.9
52.2
44.6
37
134.1
119.2
107.3
97.5
89.4
82.5
76.6
71.5
67.1
63.1
59.6
56.5
53.7
45.8
38
137.8
122.4
110.2
100.2
91.8
84.8
78.7
73.5
68.9
64.8
61.2
58.0
55.1
47.0
39
141.4
125.7
113.1
102.8
94.3
87.0
80.8
75.4
70.7
66.5
62.8
59.5
56.6
48.3
40
145.0
128.9
116.0
105.5
96.7
89.2
82.9
77.3
72.5
68.2
64.4
61.1
58.0
49.5
41
148.6
132.1
118.9
108.1
99.1
91.5
84.9
79.3
74.3
69.9
66.1
62.6
59.5
50.8
42
152.3
135.3
121.8
110.7
101.5
93.7
87.0
81.2
76.1
71.6
67.7
64.1
60.9
52.0
43
155.9
138.6
124.7
113.4
103.9
95.9
89.1
83.1
77.9
73.4
69.3
65.6
62.4
53.2
44
159.5
141.8
127.6
116.0
106.3
98.2
91.1
85.1
79.8
75.1
70.9
67.2
63.8
54.5
45
163.1
145.0
130.5
118.6
108.8
100.4
93.2
87.0
81.6
76.8
72.5
68.7
65.3
55.7
46
166.8
148.2
133.4
121.3
111.2
102.6
95.3
88.9
83.4
78.5
74.1
70.2
66.7
57.0
47
170.4
151.4
136.3
123.9
113.6
104.8
97.4
90.9
85.2
80.2
75.7
71.7
68.2
58.2
48
174.0
154.7
139.2
126.5
116.0
107.1
99.4
92.8
87.0
81.9
77.3
73.3
69.6
59.4
49
177.6
157.9
142.1
129.2
118.4
109.3
101.5
94.7
88.8
83.6
78.9
74.8
71.1
60.7

 

 
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bmx hubs
stems
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