Power-to-weight ratio (W/kg)

What is W/kg?

On flat roads your power mostly goes into pushing air aside. There, absolute wattage counts: someone pushing 300 watts rides faster than someone pushing 250, whatever they weigh. Uphill that flips. There most of your power goes into lifting you and your bike, and whoever delivers the most per kilo wins. Hence climbers are light and sprinters are allowed to be heavy.

For orientation: recreational riders often sit somewhere between 2 and 3 W/kg at threshold, trained amateurs around 3 to 4, and professionals well above that. Such numbers only mean something together with a duration: 6 W/kg for one minute is a completely different thing from 6 W/kg held for an hour. So always state which duration a value belongs to.

How do you improve your W/kg?

There are two levers: more power, or less weight. The first is almost always the better one. You build watts with targeted training, and that makes you faster on every kind of terrain. Losing weight only helps uphill, and it costs you performance as soon as you eat too little: too little energy costs muscle mass, recovery, hormonal balance and bone health. A better W/kg number reached by weakening yourself is no gain at all.

So watch the trend of your power at a stable weight, and be careful with target numbers on the scale. If you do want to lose weight, do it outside your hard training blocks, slowly, and with enough protein and carbohydrate around your sessions. If you are unsure whether it is wise, talk to a sports dietitian — this is exactly the area where well-meant weight loss sets athletes back more often than it moves them forward.

How Trimetra personalises this

Trimetra works out your W/kg from your own power anchor (FTP or Critical Power: both an estimate of your power around threshold) and your most recent weigh-in, and uses that ratio in the time band on a climb, among other places. If your last weigh-in is too old, the app still shows your watts but deliberately no W/kg — a stale weight would quietly skew a climb projection. In the what-if simulation you can see for yourself what a few kilos or a few watts would do on a specific climb, without changing your profile.