Power-to-Weight Calculator

Power-to-weight is the number that decides who drops who on a climb. It takes your FTP in watts and divides it by your body weight in kilograms, and it predicts road-race and climbing performance better than raw watts ever will. The calculator above turns those two inputs into your W/kg plus the rider band you fall into.

What W/kg is

Power-to-weight is FTP divided by body weight. A 280-watt FTP on a 70 kg rider is 4 W/kg. The same 280 watts on an 85 kg rider is 3.3 W/kg. Same engine, different car.

• FTP in watts: your Functional Threshold Power, the figure from a recent test.
• Body weight in kilograms: weigh yourself in the morning, before food, in the same state you ride.

On the flat, raw watts win because aero drag dominates. The moment the road tilts up, you are lifting your own mass against gravity, and the watts you carry per kilo is what moves you. That is why a light rider with modest watts climbs past a heavy rider with a bigger number.

Reading your number

The bands are rough, but they tell you where you stand at threshold power.

• Around 2 W/kg: untrained or new to structured riding.
• Around 3 W/kg: a trained club rider who rides most weeks.
• Around 4 W/kg: a strong amateur racer holding their own in a fast group.
• 5 W/kg and up: elite territory, the pointy end of any race.

Move your number up two ways. Raise FTP with threshold and VO2max work. Or drop weight without losing power, which is the harder road and the one most riders get wrong. A kilo lost is real W/kg gained only if the watts stay put.

The catch

W/kg is built on FTP, so it is only as honest as your last FTP test. A number from three months ago, or from a test you blew up halfway through, gives you a W/kg that flatters or lies. Retest every four to six weeks during a focused block and run the new figure here.

Weight matters too. Step on the scale in a consistent state, not after a big meal, not dehydrated post-ride. A 2 kg swing in measured weight shifts your number enough to put you in the wrong band.

Power-to-weight is one number. For how power, normalized power, and intensity tie together across a full ride, read the normalized power guide.