Bike gear ratio calculation method



The bike gear ratio is the number of the chainring teeth number divided by the sprocket teeth number for one turn of crank that will generate a distance.

For example: for a road bike with wheels diameter 700 mm with a 52 theet chainring and a 12 teeth sprocket , the distance generated by one turn of crank will be 9.52 meters. The rotation speed of the cranks is generally between 50 and 100 turns per minute so a bicycle speed with this gear ratio betwwen 28.5 km/h and 57.1 km/h .



Why calculate your gear ratio ?

This parameter is one of the most important criteria when you are looking for performance or when you want to prepare an unusual, such as a race. Choosing the right gear means personalizing your shiffting in order to find the best personol compromize between strength and velocity so it's guaranteed to make the best of your own potential.

 



Here is the theoretical calculation formula for defining this distance:

A/ the perimeter of a 700 mm diameter wheel comes from the formula 2 x ft x radius = 2198 mm

B/ the reduction ratio is 52 / 12 = 4.33

C/ the calculation of the distance traveled for crank turn with 700 mm diameter wheels, a 52 teeth chainring and a 12 teeth sprocket is 2198 x 4.33 = 9525 mm so 9.52 meters.

D/ for a pedal frequency of 70 turns per minute, the bike speed will be ((9,52 x 70) x 60 minutes) = 39,9 km/h

Please note, this formula does not take into account the thickness of the tires, if you want an accurate distance value, take a wheel turn on the ground and measure the distance, you will then have the exact value of the wheel perimeter.

This method works for all chainrings shape: oval or round and all brands: shimano, sram, campagnolo, rotor, TA, Stronglight,...



Bicycle gears progress

The number of sprockets on a cassette has quickly changed in recent years from 5 to 12 speed today. This progess has permited the progressiveness of the gear change in the number of teeth of the largest sprocket. Today the number of teeth of the smallest sprocket from a cassette has decreased, it is now possible to obtain a cassette provided with a small sprocket of 10 teeth and a large sprocket of 50 teeth, this range width allows to generate new gears values and remove one or two chainrings. Indeed the improvement of the flexibility the chains, the increase of the rear derailleur makes it possible to create shiftings provided with a chainring and 12 sprockets on the same cassette, the advantage of this type of configuration is to be able to remove the chainrings shifter, the front derailleur and one or two chainrings, the weight gain is obvious. 

Technical progress now makes it possible with a chainring to obtain the same gear as a shifting fitted with three chainrings.



Gear shifts and cycling competitions

In order to limit the power of the youngest, the gear of the minimes is limited to 7.01 meters corresponding to a chainring of 46 teeth and a sprocket of 14 teeth. For cadets, the distance for a crank turn is limited to 7.62 meters, the equivalent of a 50 teeth chainring and a 14 teeth sprocket. Since 2020, juniors are no longer limited in gear in France and the restriction will be lifted by the UCI in 2021.

Here are some examples of gears ratio used by professionnal cyclists:

  • 36x28 for the ascent of the Mont Ventoux.
  • 55x11 for a time trial

 



 

Gear ratio chart



Based on the theoretical formula for the bike gear ratio calculation, here is a indicative table of bike gear ratio for wheels diameter 700 mm without taking into account the thickness of the tires:

A/ Chainring until 30 teeth, distance in meter traveled for a crank turn:

Chainring teeth number
20 21 22 23 24 25 26 27 28 29 30

Sprocket

teeth number

11 4 4,2 4,4 4,6 4,8 5 5,2 5,4 5,59 5,79 5,99
12 3,66 3,85 4,03 4,21 4,4 4,58 4,76 4,95 5,13 5,31 5,5
13 3,38 3,55 3,72 3,89 4,06 4,23 4,40 4,57 4,73 4,90 5,07
14 3,14 3,30 3,45 3,61 3,77 3,93 4,08 4,24 4,40 4,55 4,71
15 2,93 3,08 3,22 3,37 3,52 3,66 3,81 3,96 4,10 4,25 4,40
16 2,75 2,88 3,02 3,16 3,30 3,43 3,57 3,71 3,85 3,98 4,12
17 2,59 2,72 2,84 2,97 3,10 3,23 3,36 3,49 3,62 3,75 3,88
18 2,44 2,56 2,69 2,81 2,93 3,05 3,17 3,30 3,42 3,54 3,66
19 2,31 2,43 2,55 2,66 2,78 2,89 3,01 3,12 3,24 3,35 3,47
20 2,2 2,31 2,42 2,53 2,64 2,75 2,86 2,97 3,08 3,19 3,30
21 2,09 2,20 2,30 2,41 2,51 2,62 2,72 2,83 2,93 3,04 3,14
22 2 2,10 2,20 2,30 2,40 2,50 2,60 2,70 2,80 2,90 3
23 1,91 2,01 2,10 2,20 2,29 2,39 2,48 2,58 2,68 2,77 2,87
24 1,83 1,92 2,01 2,11 2,20 2,29 2,38 2,47 2,56 2,66 2,75
25 1,76 1,85 1,93 2,02 2,11 2,20 2,29 2,37 2,46 2,55 2,64
26 1,69 1,78 1,86 1,94 2,03 2,11 2,20 2,28 2,37 2,45 2,54
27 1,63 1,71 1,79 1,87 1,95 2,04 2,12 2,20 2,28 2,36 2,44
28 1,57 1,65 1,73 1,81 1,88 1,96 2,04 2,12 2,20 2,28 2,36
29 1,52 1,59 1,67 1,74 1,82 1,89 1,97 2,05 2,12 2,20 2,27
30 1,47 1,54 1,61 1,69 1,76 1,83 1,90 1,98 2,05 2,12 2,20
31 1,42 1,49 1,56 1,63 1,70 1,77 1,84 1,91 1,99 2,06 2,13
32 1,37 1,44 1,51 1,58 1,65 1,72 1,79 1,85 1,92 1,99 2,06
33 1,33 1,40 1,47 1,53 1,60 1,67 1,73 1,80 1,86 1,93 2
34 1,29 1,36 1,42 1,49 1,55 1,62 1,68 1,75 1,81 1,87 1,94
35 1,26 1,32 1,38 1,44 1,51 1,57 1,63 1,70 1,76 1,82 1,88
36 1,22 1,28 1,34 1,40 1,47 1,53 1,59 1,65 1,71 1,77 1,83
37 1,19 1,25 1,31 1,37 1,43 1,49 1,54 1,60 1,66 1,72 1,78
38 1,16 1,21 1,27 1,33 1,39 1,45 1,50 1,56 1,62 1,68 1,74
39 1,13 1,18 1,24 1,30 1,35 1,41 1,47 1,52 1,58 1,63 1,69
40 1,10 1,15 1,21 1,26 1,32 1,37 1,43 1,48 1,54 1,59 1,65

B/ Chainring until 40 teeth, distance in meter traveled for a crank turn: 

Chainring teeth number
31 32 33 34 35 36 37 38 39 40

Sprocket

teeth number

11 6,19 6,39 6,59 6,79 6,99 7,19 7,39 7,59 7,79 7,99
12 5,68 5,86 6,04 6,23 6,41 6,59 6,78 6,96 7,14 7,33
13 5,24 5,41 5,58 5,75 5,92 6,09 6,26 6,42 6,59 6,76
14 4,87 5,02 5,18 5,34 5,50 5,65 5,81 5,97 6,12 6,28
15 4,54 4,69 4,84 4,68 5,13 5,28 5,42 5,57 5,71 5,86
16 4,26 4,40 4,53 4,67 4,81 4,95 5,08 5,22 5,36 5,50
17 4,01 4,14 4,27 4,40 4,53 4,65 4,78 4,91 5,04 5,17
18 3,79 3,91 4,03 4,15 4,27 4,40 4,52 4,64 4,76 4,88
19 3,59 3,70 3,82 3,93 4,05 4,16 4,28 4,40 4,51 4,63
20 3,41 3,52 3,63 3,74 3,85 3,96 4,07 4,18 4,29 4,40
21 3,24 3,35 3,45 3,56 3,66 3,77 3,87 3,98 4,08 4,19
22 3,10 3,20 3,30 3,40 3,50 3,60 3,70 3,80 3,90 4,00
23 2,96 3,06 3,15 3,25 3,34 3,44 3,54 3,63 3,73 3,82
24 2,84 2,93 3,02 3,11 3,21 3,30 3,39 3,48 3,57 3,66
25 2,73 2,81 2,90 2,99 3,08 3,17 3,25 3,34 3,43 3,52
26 2,62 2,71 2,79 2,87 2,96 3,04 3,13 3,21 3,30 3,38
27 2,52 2,61 2,69 2,77 2,85 2,93 3,01 3,09 3,17 3,26
28 2,43 2,51 2,59 2,67 2,75 2,83 2,90 2,98 3,06 3,14
29 2,35 2,43 2,50 2,58 2,65 2,73 2,80 2,88 2,96 3,03
30 2,27 2,34 2,42 2,49 2,56 2,64 2,71 2,78 2,86 2,93
31 2,20 2,27 2,34 2,41 2,48 2,55 2,62 2,69 2,77 2,84
32 2,13 2,20 2,27 2,34 2,40 2,47 2,54 2,61 2,68 2,75
33 2,06 2,13 2,20 2,26 2,33 2,40 2,46 2,53 2,60 2,66
34 2 2,07 2,13 2,20 2,26 2,33 2,39 2,46 2,52 2,59
35 1,95 2,01 2,07 2,14 2,20 2,26 2,32 2,39 2,45 2,51
36 1,89 1,95 2,01 2,08 2,14 2,20 2,26 2,32 2,38 2,44
37 1,84 1,90 1,96 2,02 2,08 2,14 2,20 2,26 2,32 2,38
38 1,79 1,85 1,91 1,97 2,02 2,08 2,14 2,20 2,26 2,31
39 1,75 1,80 1,86 1,92 1,97 2,03 2,09 2,14 2,20 2,25
40 1,70 1,76 1,81 1,87 1,92 1,98 2,03 2,09 2,14 2,20

C/ Chainring until 50 teeth, distance travelled for a crank turn:

Chainring teeth number
41 42 43 44 45 46 47 48 49 50

Sprocket

teeth number

11 8,19 8,39 8,59 8,79 8,99 9,19 9,39 9,59 9,79 9,99
12 7,51 7,69 7,88 8,06 8,24 8,43 8,61 8,79 8,98 9,16
13 6,93 7,10 7,27 7,44 7,61 7,78 7,95 8,12 8,28 8,45
14 6,44 6,59 6,75 6,91 7,07 7,22 7,38 7,54 7,69 7,85
15 6,01 6,15 6,30 6,45 6,59 6,74 6,89 7,03 7,18 7,33
16 5,63 5,77 5,91 6,04 6,18 6,32 6,46 6,59 6,73 6,87
17 5,30 5,43 5,56 5,69 5,82 5,95 6,08 6,21 6,34 6,46
18 5,01 5,13 5,25 5,37 5,50 5,62 5,74 5,86 5,98 6,11
19 4,74 4,86 4,97 5,09 5,21 5,32 5,44 5,55 5,67 5,78
20 4,51 4,62 4,73 4,84 4,95 5,06 5,17 5,28 5,39 5,50
21 4,29 4,40 4,50 4,61 4,71 4,81 4,92 5,02 5,13 5,23
22 4,10 4,20 4,30 4,40 4,50 4,60 4,70 4,80 4,90 5,00
23 3,92 4,01 4,11 4,20 4,30 4,40 4,49 4,59 4,68 4,78
24 3,75 3,85 3,94 4,03 4,12 4,21 4,30 4,40 4,49 4,58
25 3,60 3,69 3,78 3,87 3,96 4,04 4,13 4,22 4,31 4,40
26 3,47 3,55 3,64 3,72 3,80 3,89 3,97 4,06 4,14 4,23
27 3,34 3,42 3,50 3,58 3,66 3,74 3,83 3,91 3,99 4,07
28 3,22 3,30 3,38 3,45 3,53 3,61 3,69 3,77 3,85 3,93
29 3,11 3,18 3,26 3,33 3,41 3,49 3,56 3,64 3,71 3,79
30 3,00 3,08 3,15 3,22 3,30 3,37 3,44 3,52 3,59 3,66
31 2,91 2,98 3,05 3,12 3,19 3,26 3,33 3,40 3,47 3,55
32 2,82 2,88 2,95 3,02 3,09 3,16 3,23 3,30 3,37 3,43
33 2,73 2,80 2,86 2,93 3,00 3,06 3,13 3,20 3,26 3,33
34 2,65 2,72 2,78 2,84 2,91 2,97 3,04 3,10 3,17 3,23
35 2,57 2,64 2,70 2,76 2,83 2,89 2,95 3,01 3,08 3,14
36 2,50 2,56 2,63 2,69 2,75 2,81 2,87 2,93 2,99 3,05
37 2,44 2,50 2,55 2,61 2,67 2,73 2,79 2,85 2,91 2,97
38 2,37 2,43 2,49 2,55 2,60 2,66 2,72 2,78 2,83 2,89
39 2,31 2,37 2,42 2,48 2,54 2,59 2,65 2,71 2,76 2,82
40 2,25 2,31 2,36 2,42 2,47 2,53 2,58 2,64 2,69 2,75

D/ Chainring until 60 teeth, distance travelled for a crank turn:

Chainring teeth number
51 52 53 54 55 56 57 58 59 60

Sprocket

teeth number

11 10,19 10,39 10,59 10,79 10,99 11,19 11,39 11,59 11,79 11,99
12 9,34 9,52 9,71 9,89 10,07 10,26 10,44 10,62 10,81 10,99
13 8,62 8,79 8,96 9,13 9,30 9,47 9,64 9,81 9,98 10,14
14 8,01 8,16 8,32 8,48 8,64 8,79 8,95 9,11 9,26 9,42
15 7,47 7,62 7,77 7,91 8,06 8,21 8,35 8,50 8,65 8,79
16 7,01 7,14 7,28 7,42 7,56 7,69 7,83 7,97 8,11 8,24
17 6,59 6,72 6,85 6,98 7,11 7,24 7,37 7,50 7,63 7,76
18 6,23 6,35 6,47 6,59 6,72 6,84 6,96 7,08 7,20 7,33
19 5,90 6,02 6,13 6,25 6,36 6,48 6,59 6,71 6,83 6,94
20 5,60 5,71 5,82 5,93 6,04 6,15 6,26 6,37 6,48 6,59
21 5,34 5,44 5,55 5,65 5,76 5,86 5,97 6,07 6,18 6,28
22 5,10 5,20 5,30 5,40 5,50 5,59 5,69 5,79 5,89 5,99
23 4,87 4,97 5,06 5,16 5,26 5,35 5,45 5,54 5,64 5,73
24 4,67 4,76 4,85 4,95 5,04 5,13 5,22 5,31 5,40 5,50
25 4,48 4,57 4,66 4,75 4,84 4,92 5,01 5,10 5,19 5,28
26 4,31 4,40 4,48 4,57 4,65 4,73 4,82 4,90 4,99 5,07
27 4,15 4,23 4,31 4,40 4,48 4,56 4,64 4,72 4,80 4,88
28 4,00 4,08 4,16 4,24 4,32 4,40 4,47 4,55 4,63 4,71
29 3,87 3,94 4,02 4,09 4,17 4,24 4,32 4,40 4,47 4,55
30 3,74 3,81 3,88 3,96 4,03 4,10 4,18 4,25 4,32 4,40
31 3,62 3,69 3,76 3,83 3,90 3,97 4,04 4,11 4,18 4,25
32 3,50 3,57 3,64 3,71 3,78 3,85 3,92 3,98 4,05 4,12
33 3,40 3,46 3,53 3,60 3,66 3,73 3,80 3,86 3,93 4,00
34 3,30 3,36 3,43 3,49 3,56 3,62 3,68 3,75 3,81 3,88
35 3,20 3,27 3,33 3,39 3,45 3,52 3,58 3,64 3,71 3,77
36 3,11 3,17 3,24 3,30 3,36 3,42 3,48 3,54 3,60 3,66
37 3,03 3,09 3,15 3,21 3,27 3,33 3,39 3,45 3,50 3,56
38 2,95 3,01 3,07 3,12 3,18 3,24 3,30 3,35 3,41 3,47
39 2,87 2,93 2,99 3,04 3,10 3,16 3,21 3,27 3,33 3,38
40 2,80 2,86 2,91 2,97 3,02 3,08 3,13 3,19 3,24 3,30