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Cycling Power Calculator

Estimate required pedaling power in watts from weight, speed, and gradient – with W/kg and the components for gradient, rolling, and air resistance plus VAM (meters per hour).

Available

Inputs

Enter values

Live
Power from Ride DataWatts and W/kg from mass, speed, and gradient

Ride Data

Mass, speed, and gradient.

kg

Rider, bike, clothing, and luggage combined.

km/h
%

Negative values for descent.

km/h

Enter tailwind as negative value.

Load example

For illustration only – your own calculation is what counts.

Explanation

How Cycling Power Calculator works

The cycling power calculator estimates how much pedaling power a particular ride requires. The basis is an established physical bicycle model that separately accounts for the three riding resistances. Additionally, the VAM mode calculates climbing speed on ascents.

The Power Model

Required PowerP = (F_Gradient + F_Rolling + F_Air) × v ÷ Drivetrain Efficiency

The three resistance forces are multiplied by speed and divided by drivetrain efficiency. Air resistance increases with the square of airspeed.

VAMVAM = Elevation Gain ÷ Time (in hours)

Average climbing speed in meters per hour.

Practice

Practical examples

For illustration only – your own calculation is what counts.

Watts on an 8% ramp

Rider and bike together weigh 80 kg, ridden at 20 km/h on an 8% steep ramp in calm air.

Result: About 413 W are required (about 5.2 W/kg). The gradient component clearly dominates over air and rolling resistance.

VAM on a climb

A climb with 800 meters elevation gain is completed in 40 minutes.

Result: This corresponds to a VAM of 1200 meters per hour – very good climbing level.

Notes

Common mistakes

  1. Entering only body weight

    Those who forget bike weight underestimate required power on climbs.

    Enter total mass of rider, bike, clothing, and luggage.

  2. Neglecting wind

    Without wind input, air resistance is significantly underestimated with headwind.

    Enter noticeable headwind; tailwind as negative value.

FAQ

Frequently asked questions

How is power calculated?

Via a physical bicycle model (Martin et al. 1998): Required power is the sum of gradient resistance, rolling resistance, and air resistance, divided by drivetrain efficiency. Each component is determined from mass, speed, gradient, and air values.

What assumptions are included?

For rolling resistance (Crr ≈ 0.005), drag area (CdA ≈ 0.32 m²), air density (1.225 kg/m³), and drivetrain efficiency (0.975), typical road values are assumed. Tires, position, surface, and altitude noticeably change these values.

What does W/kg mean?

Watts per kilogram relates power to weight. On climbs and during accelerations, this relative value is more decisive than absolute watts because mass must be moved. Here total mass (rider + bike) is used.

What is VAM?

VAM (velocità ascensionale media) is average climbing speed in meters per hour. It describes how quickly elevation is gained on a climb and can be compared well between climbs.

How does headwind affect?

Headwind increases airspeed and thus air resistance disproportionately (it enters quadratically). Even moderate wind can sharply increase required power; tailwind is entered as negative headwind.

How accurate is the result?

It is a physical estimate for steady riding. Without measured CdA, actual Crr, and real air density, the value differs from a power meter. For comparisons and target estimates, it is still meaningful.

Limits

Limitations

  • Crr, CdA, air density, and efficiency are standard assumptions and can vary greatly in reality.
  • The model is valid for steady riding, not for accelerations.

Sources

Sources and references

  • Martin, J. C. et al. (1998): Validation of a Mathematical Model for Road Cycling PowerJournal of Applied Biomechanics 14:276–291

    Validated power model for road cycling with the three riding resistances.

    Retrieved: 09/23/2026 · Verified on: 09/23/2026
  • VAM – velocità ascensionale mediaSportmedizinische Trainingslehre (Ferrari)

    Definition of average climbing speed in meters per hour.

    Retrieved: 09/23/2026 · Verified on: 09/23/2026