What this calculator does
Power-to-weight is power divided by body weight, in watts per kilogram. It is the figure that predicts climbing performance, because gravity acts on the whole rider and bike while the power available is whatever the legs produce.
A rider holding 250 W at 75 kg is at 3.33 W/kg, which places them in the trained range. On the flat, raw watts matter more than the ratio, since air resistance depends on frontal area rather than mass. This is why heavy riders can be fast on flat ground and lose time the moment the road tilts up.
The formula
Power in watts is divided by body weight in kilograms. The category is read from the Coggan power-profiling bands, which are approximate and depend on both the duration the power is held for and the rider sex. The bands here should be read as a rough orientation rather than a classification.
| Term | Meaning |
|---|---|
| W/kg | Watts per kilogram, power divided by body weight. |
| FTP | Functional threshold power, roughly the power sustainable for an hour, which is the usual basis for these comparisons. |
| Coggan bands | The power-profiling categories from Training and Racing with a Power Meter. |
| Duration dependence | W/kg for a 5 second sprint is far higher than for an hour, so the two are not comparable. |
The inputs explained
| Field | What to enter |
|---|---|
| Power (e.g. FTP) (W) | Power output in watts. For meaningful comparison use functional threshold power rather than a short-burst figure. |
| Body weight (kg) | Body weight in kilograms. Some comparisons use rider plus bike, which lowers the figure noticeably. |
When to use it
Estimating climbing ability
Power-to-weight is the dominant factor on a sustained climb, and it predicts relative performance better than absolute power does.
Tracking training progress
The ratio moves with both power and weight, so it captures progress that either figure alone would miss.
Comparing riders of different sizes
Two riders with very different absolute power can be closely matched uphill, which the ratio shows and raw watts do not.
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
What power-to-weight does each power output give?
A fixed rider weight across a range of sustained power outputs.
| Power output | Power-to-weight | Approximate category |
|---|---|---|
| 150 W | 2.00 W/kg | Recreational |
| 250 W | 3.33 W/kg | Trained / Cat 4 |
| 350 W | 4.67 W/kg | Well-trained / Cat 3 |
| 450 W | 6.00 W/kg | Exceptional / professional |
Questions
What is a good power-to-weight ratio?
Roughly, 2 to 3 W/kg at threshold is recreational, 3 to 4 is a keen amateur, 4 to 5 is a strong club racer and above 5.5 is approaching professional. These bands assume power held for around an hour and differ between men and women, so treat them loosely.
Should I include the bike weight?
It depends what you are comparing. Pure rider W/kg is the standard figure and is what these bands assume. For predicting climbing speed, rider plus bike plus kit is the honest total, and adding 8 to 10 kg lowers the ratio noticeably.
Does power-to-weight matter on the flat?
Much less. On flat ground the main resistance is aerodynamic, which depends on frontal area and speed rather than on mass. Absolute watts predict flat speed far better, which is why large riders can be fast on the flat and lose time on climbs.
Is losing weight the fastest way to improve it?
It raises the ratio arithmetically, but not without limits. Losing weight usually costs some power as well, and cutting too far harms training capacity, recovery and health. For most riders, raising power is the more durable route and the one with fewer trade-offs.
For gearing on climbs, see the bike gear calculator. For e-bike range, see the e-bike range calculator.