Categories follow the Coggan power profile for male cyclists at threshold. Use them as a rough map, not a verdict.
Track it across a season A single W/kg reading says little. WattLog.PRO keeps the whole history, so you can see whether the ratio is improving because power went up or only because weight went down.
Open WattLog.PROWhy the ratio matters
Going uphill, almost all of your power fights gravity, and gravity scales with your mass. Two riders at 300 watts climb at very different speeds if one weighs 60 kilograms and the other 85. That is why power-to-weight, not raw power, predicts climbing performance - and why the ratio is the standard way of comparing cyclists of different sizes.
On the flat the logic inverts. There, power fights air resistance, which scales with frontal area rather than mass, so the bigger rider with more absolute watts usually wins. A heavy sprinter with a poor W/kg can be untouchable on a flat run-in and dropped on the first serious gradient. Neither number is better; they answer different questions.
Improving it honestly
There are only two levers: raise power or lower mass. Raising power is slower but keeps everything else intact. Losing weight looks like the faster route on a spreadsheet, and for a while it is - but past a certain point power starts falling with the weight, and the ratio stalls or reverses while you feel progressively worse.
Compare yourself to your own history rather than to a category table. Categories are drawn from testing data and vary with age, sex and testing conditions. A ratio that climbed from 3.2 to 3.6 across a winter is unambiguously good news, whatever label either number carries.
Frequently asked questions
What is a good watts per kg for cycling?
A fit recreational rider is usually somewhere between 2.5 and 3.5 W/kg at threshold. Strong amateur racers sit around 4 to 4.5, and professional road cyclists exceed 5.5. Context matters more than the label: your own trend over a season is the number worth watching.
Should I use FTP or peak power for this?
FTP for sustained climbing, which is what the ratio is usually about. Peak power over five minutes or one minute gives a different and also useful ratio for short steep climbs and attacks. Just be consistent about which one you quote, because the numbers differ a lot.
Does bike weight count?
Not in this calculation, which uses body weight by convention so riders can be compared. Bike weight absolutely affects how fast you actually climb, though - for real-world speed on a gradient, use the power-to-speed calculator, which takes total system weight.