Motorcycle Sprocket Calculator
Compare stock and modified sprockets: the change in wheel torque, cruising rpm, top speed and speedometer, plus whether your chain still fits the axle slot.
Stock vs. Modified Gearing
2. Stock setup
3. Your change
4. Your bike's figures
Final Ratio
3.133:1
Stock:2.813:1
Wheel Torque
+11.4%
Same engine torque
Rpm at Cruise
6,907
Change:+707 rpm
Top Speed (rev-limited)
147.2mph
Change:-10.2%
Speedometer
Error
+11.4%
Gearbox-driven only
At 70 mph, dash reads
78mph
Correction factor
×0.8976
Dash × factor = true
This applies if the speedometer is driven from the gearbox output. A front-wheel sensor isn't affected by sprocket changes. Top speed assumes the bike is limited by rpm; a drag-limited bike won't gain or lose as much.
Chain and axle position
The stock 114-link chain still fits: axle moves -4.9 mm.
| Sprocket | Stock | Modified | Outside Ø change |
|---|---|---|---|
| Front sprocket | 16T · 89.3 mm | 15T · 84.2 mm | -5.1 mm |
| Rear sprocket | 45T · 236.5 mm | 47T · 246.7 mm | +10.1 mm |
| Wear (GCD) | GCD 1 | GCD 1 | GCD 1 spreads wear |
A smaller front sprocket shrinks the outside diameter, which helps case clearance. Check the rear sprocket against the chain guard and slider.
Common Sprocket Changes Compared
Example: a 16/45T bike on 525 chain with 114 links, cruising at 6,200 rpm at 70 mph. Each row is calculated with this page's engine. For the effect of a change on speed across the rev range, use the sprocket speed calculator.
| Change | Sprockets | Final ratio | Wheel torque | Cruise rpm | Top speed |
|---|---|---|---|---|---|
| −1F | 15T / 45T | 3:1 | +6.7% | 6,613 (+413) | -6.3% |
| +1F | 17T / 45T | 2.647:1 | -5.9% | 5,835 (-365) | +6.3% |
| +1R | 16T / 46T | 2.875:1 | +2.2% | 6,338 (+138) | -2.2% |
| +2R | 16T / 47T | 2.938:1 | +4.4% | 6,476 (+276) | -4.3% |
| −1F / +2R | 15T / 47T | 3.133:1 | +11.4% | 6,907 (+707) | -10.2% |
Chain Length and Fitment After a Change
Changing sprockets also changes how much chain you need. To work out the exact link count from your swingarm length, use the chain length calculator, or see what swapping chain families saves with the 630 to 530 and 520 chain conversion calculator.