38T × 25T
1.52
Gear ratio
Per pedal stroke 3.2 m
38×25 ratio 1.52 — 3.2 m per stroke
A 38-tooth chainring with a 25-tooth sprocket gives a ratio of 1.52. One pedal stroke carries you 3.2 m, and at 90 rpm that is 17.3 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 rpm11.5 km/h
- Cadence 80 rpm15.4 km/h
- Cadence 90 rpm17.3 km/h
- Cadence 100 rpm19.2 km/h
- Chainring
- 38T
- Sprocket
- 25T
- Gear ratio
- 1.52
- Per pedal stroke
- 3.2 m
- Gear inches
- 40
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 38×25?
1.52. One pedal stroke carries you 3.2 m, which is 40 gear inches.
Q. How fast is this gear?
At 90 rpm it works out to 17.3 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 38×28: the pedals ease off, but each stroke carries you less far.