What is cycling power measured in?

Watts, read from a power meter on the bike.

What is FTP in cycling?

Functional threshold power: roughly the power you can sustain for about an hour.

Why is power better than heart rate?

It's instant and objective, while heart rate lags and drifts with fatigue and heat.

Cycling Power (Watts) Explained

Published 7/24/2025 · 3 min read · Sport calculators

Aisha Karim — Fitness & running writer at OneKitly

Running · Training

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In short

Cycling power is how hard you're pedalling, measured in watts by a power meter. Unlike speed or heart rate, it's an instant, objective measure of effort that ignores wind and hills. A key benchmark is FTP — the power you can hold for about an hour — and training zones are set as percentages of it. Power-to-weight (watts per kilogram) matters most for climbing.

Power is the objective measure of cycling effort. Here's what watts mean, why they beat speed and heart rate, what FTP is, and why watts per kilo matter.

What power measures

Power is the rate at which you do work at the pedals, expressed in watts. A power meter, built into the pedals, crank or hub, measures the force you apply and how fast you're turning the cranks, and multiplies them into a live wattage. Push harder or spin faster and the number rises immediately. Unlike anything else on your bike computer, it tells you exactly how much effort you are producing this very second — no guessing, no lag.

Why it beats speed and heart rate

Speed lies about effort: the same 30 km/h is easy downhill with a tailwind and brutal up a climb into a headwind. Heart rate is honest but slow — it drifts up as you tire, rises in the heat, and lags behind sudden efforts by many seconds. Power has neither flaw. Two hundred watts is two hundred watts whether you're climbing, descending or fighting the wind, and it registers the instant you produce it. That's why serious cyclists train and pace by watts.

FTP and zones

The anchor for power-based training is FTP — functional threshold power — roughly the highest power you could sustain for about an hour. It's the line between efforts you can hold for a long time and ones that quickly burn you out. Once you know your FTP, training zones are defined as percentages of it: easy recovery riding well below it, endurance a bit under, threshold work right around it, and short, painful intervals above. Zones turn a vague 'ride hard' into a precise target.

Watts per kilogram

On the flat, raw watts largely decide your speed, but the moment the road tilts up, weight enters the equation. Climbing is mostly about lifting your body and bike against gravity, so what matters is power-to-weight: watts divided by kilograms. A 60 kg rider at 240 W (4 W/kg) will out-climb an 80 kg rider at 280 W (3.5 W/kg) despite the lower raw power. It's why climbers are lean, and why cyclists track W/kg as closely as watts alone.

Worked with our own calculator

Cycling power calculator

Given

Speed (km/h): 27
Rider + bike weight (kg): 72

Result

Power: 109 W

These figures are produced by the calculator below, not typed in by hand — they are recomputed whenever the tool changes.

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Frequently asked questions

What is cycling power measured in?: Watts, read from a power meter on the bike.
What is FTP in cycling?: Functional threshold power: roughly the power you can sustain for about an hour.
Why is power better than heart rate?: It's instant and objective, while heart rate lags and drifts with fatigue and heat.

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