Power to weight ratio for cycling
This cycling power to weight ratio calculator gives your W/kg together with climbing speed: 250 W at 75 kg is 3.33 W/kg and takes you up a 7 % gradient at about 13.5 km/h.
Example: What would you like to calculate: Speed from my power · Power 250 W · Rider weight 75 kg · Weight of bike and luggage 9 kg · Gradient 7 % · Riding position: On the hoods · Road and tyres: Smooth asphalt, road tyres → Result: 3.33 W/kg gives 13.5 km/h on a 7.0 % gradient. Source: Wikipedia – Bicycle performance (efficiency, power in W/kg: 1.0 / 2.2 / 3.0 / 5 / 6.6 W/kg at threshold power). Updated: .
How it is calculated
Power to weight ratio is sustained power in watts divided by body weight in kilograms. 250 W at 75 kg gives 3.33 W/kg. On climbs it decides your speed, while on the flat absolute power counts for more.
How it is calculated
The calculator solves the physics of riding: power at the rear wheel has to overcome gravity on the slope, rolling resistance and air resistance. Gravity grows with weight and gradient, rolling resistance with weight and tyres, air resistance with the square of speed and riding position (CdA). 3 % is lost in the drivetrain between pedal and wheel. Power gives speed, and speed gives vertical metres per hour (VAM), the usual measure for climbers.
Putting the numbers in context
Reference values refer to threshold power over about an hour: roughly 1.0 W/kg for novice women, 2.2 W/kg for untrained men, 3.0 W/kg for good fitness, 5 W/kg for excellent amateurs and 6.6 W/kg for top-class athletes.
- The weight of bike and luggage counts in full on climbs, so it has its own line.
- An upright position costs a lot of speed on the flat and hardly any on a steep climb.
- The table shows how your power turns into speed on gradients from 0 to 12 %.
Frequently asked questions
How do you calculate watts per kilo?
Power in watts divided by body weight in kg: 280 W at 70 kg is 4.0 W/kg.
How many watts per kilo is good?
As a guide, for one-hour power about 3 W/kg is good fitness and 5 W/kg is excellent for amateurs. Top athletes reach 6.6 W/kg and more.
How fast do I climb at 3 watts per kilo?
On a 7 % gradient about 12 km/h, on 10 % about 9 km/h (75 kg rider plus 9 kg bike). The calculator takes your weight, bike and position into account.
Sources and legal basis
- Wikipedia – Bicycle performance (efficiency, power in W/kg: 1.0 / 2.2 / 3.0 / 5 / 6.6 W/kg at threshold power)
- Wikipedia – Power-to-weight ratio (Leistungsgewicht, Berechnung in W/kg)
- Wikipedia – Rolling resistance (Rollwiderstandsbeiwert Crr von Fahrradreifen)
- Wikipedia – Drag area (Luftwiderstand CdA)
As of: · Editorial policy
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