40T × 15T
2.667
Gear ratio
Per pedal stroke 5.613 m
40×15 ratio 2.667 — 5.613 m per stroke
A 40-tooth chainring with a 15-tooth sprocket gives a ratio of 2.667. One pedal stroke carries you 5.613 m, and at 90 rpm that is 30.3 km/h.
Speed
Speed is the ratio multiplied by cadence. Grinding a big gear slowly and spinning a small one quickly give the same speed, but legs last far longer doing the second — which is why most riders pick the gear that keeps them near 80 to 90 revolutions a minute.
- Cadence 60 rpm20.2 km/h
- Cadence 80 rpm26.9 km/h
- Cadence 90 rpm30.3 km/h
- Cadence 100 rpm33.7 km/h
- Chainring
- 40T
- Sprocket
- 15T
- Gear ratio
- 2.667
- Per pedal stroke
- 5.613 m
- Gear inches
- 70.1
Nearby cells
Same chainring, other sprockets
Same sprocket, other chainrings
Worth knowing
- The ratio is the chainring divided by the sprocket — bigger means harder and further.
- Two combinations with the same ratio are the same gear, whatever the tooth counts.
- Speed is ratio times cadence, so neither number settles it alone.
- These figures assume 700×25C wheels with a 2,105 mm circumference.
Common questions
Q. What is the ratio of 40×15?
2.667. One pedal stroke carries you 5.613 m, which is 70.1 gear inches.
Q. How fast is this gear?
At 90 rpm it works out to 30.3 km/h. Speed scales with cadence, so 60 rpm gives two thirds of that and 100 rpm a little more.
Q. Is there another combination that feels the same?
No other combination in this table sits within 1 % of this ratio.
Q. What happens one sprocket lighter?
You land on 40×16: the pedals ease off, but each stroke carries you less far.