Required power
169W
At the pedals.
How is this calculated?Free cycling tool
Cycling Power & Wattage Calculator
Use this cycling wattage calculator to find out how many watts you need to hold a target speed, or how fast you can ride at a given power. This cycling power calculator accounts for rider and bike weight, gradient, wind, riding position and tyre choice, giving you a realistic estimate of your required cycling watts in real-world conditions. Switch between Speed → Watts and Watts → Speed to use it as a bike power calculator, cycling watts calculator or cycling power-to-speed calculator.
Rider weight
75.0 kgBike + kit
9.0 kgBike, bottles, bags, shoes.
Speed
30.0 km/hHow fast you want to ride — we'll estimate the watts that takes.
Grade
0.0%Flat road.
Wind
0 km/hStill air. Drag right for a tailwind, left for a headwind.
Advanced
Elevation
100 mUsed with air temperature to set air density (ISO 2533).
Air temperature
15°CCustom CdA
0.360 m²Overrides the position preset. Typical hoods 0.32–0.40 m².
Custom Crr
0.0055Overrides the tyre preset. Smooth road tyres are around 0.004.
Drivetrain efficiency
97.6%Martin et al. used 97.6% chain efficiency.
Training metrics
optional
Functional threshold power. Needed for Intensity Factor, estimated TSS and Coggan zone.
Ride duration
1 hUsed for estimated TSS and total kilojoules / Calories.
Watts per kilogram
2.26W/kg
Rider mass only, same convention as Strava / TrainingPeaks.
How is this calculated?Where your watts go
- Aero126 W
- Rolling38 W
- Gravity0 W
- Drivetrain5 W
Aero grows with the cube of speed.
Energy
609kJ/h
617 kcal/h
How is this calculated?Share
Share this result
Knowing how many watts you need to ride at a certain speed makes it much easier to understand your effort on the bike. This cycling wattage calculator estimates the power required to hold a given speed, or the speed you can achieve at a given power, using your weight, bike, gradient, wind, riding position and tyres.
Use this cycling power calculator to work out your expected watts on flat roads, climbs, descents and into a headwind or tailwind. It also works as a cycling watts calculator, bike power calculator and cycling watt calculator, giving you a practical estimate of the power you need to maintain your target pace without relying on a power meter.
For riders who train by power, the calculator also shows watts per kilogram (W/kg) and where your power is being spent. Compare the effect of speed, weight, gradients and aerodynamics to understand why small changes in conditions can make a surprisingly large difference to your required power.
You can also switch to Watts → Speed to use it as a cycling power to speed calculator or cycling speed power calculator. Enter your available power and see how fast you could expect to ride in different conditions. When wind is involved, the difference can be substantial — a tailwind can make the same power feel dramatically faster, while a headwind can add a large amount of resistance.
The physics
Where the watts actually go
This calculator is the Martin et al. (1998) road-load model — the same equations used by Gribble, BikeCalcs and most serious cycling power estimators. Validated against SRM meters at R² = 0.97, ±2.7 W.
Gravity
On a climb you lift your mass against gravity. Power is m · g · sinθ · v. A 3% grade at 20 km/h already costs a typical rider more than 100 W — which is why we climb slower, not harder forever.
Rolling resistance
Tyres hysteresis against the road. Force is m · g · Crr · cosθ, almost independent of speed. Road tyres on tarmac sit near 0.004; knobbies on hardpack are several times that.
Aero — speed cubes watts
Drag force goes with airspeed squared, so the power to push air goes with speed cubed. That is why a few km/h on the flat is expensive, and why a lower torso (drops, aero bars) pays off more the faster you ride. The rider’s body is about 70% of the drag; the bike is the rest.
Drivetrain
Chain, pulleys and bottom-bracket bearings waste a few percent of pedal power before it reaches the rear wheel. Martin et al. measured 97.6% efficiency and a small wheel-bearing term of a few watts.
FAQ
Frequently asked questions
How does a cycling wattage calculator work?
It estimates the power you need to hold a given speed — or the speed you can hold at a given power — by adding the forces that resist you: gravity, rolling resistance, aerodynamic drag and a small drivetrain loss. Tailwind uses the Martin et al. (1998) road-load model, which matched road power meters to within about 3 W in the original validation.
How accurate is estimated cycling power without a power meter?
On a calm, steady effort the model is typically within a few percent if mass, CdA and Crr are in the right ballpark. Real rides add gusts, position changes, braking and acceleration, which this page does not simulate. Treat the number as a physics estimate, not a laboratory measurement.
What CdA should I use?
CdA is drag coefficient times frontal area. Varied and hoods sit around 0.36 m²; drops 0.27–0.36; amateur aero bars 0.22–0.28. Body size, clothing and helmet can move you 15–20% either way. Pick the position that matches how you ride, or type a measured CdA in Advanced.
What is Crr?
The coefficient of rolling resistance. It captures tyre hysteresis and road surface, not labelled width by itself — and the width bands overlap. Road slicks are typically 25–32 mm (~0.004); endurance / all-round 28–38 mm (~0.0055); gravel 32–50 mm (~0.008), including fast 32 mm gravel; mountain bike knobbies 51–66 mm / 2.0–2.6″ (~0.012). Off-road mud is much higher.
How do I convert watts to speed?
Switch the calculator to Watts → speed. Because aero drag grows with the square of airspeed, power grows roughly with the cube of speed, so we invert the Martin equation numerically (Newton–Raphson) rather than with a single algebraic formula.
What is Intensity Factor / TSS?
Intensity Factor is your power divided by FTP. Estimated Training Stress Score is hours × IF² × 100, so one hour at FTP is 100 TSS. Those figures assume a perfectly steady effort. Real TSS uses Normalized Power from a variable ride file, which we do not invent from a single speed.
Does Tailwind GPS use this model on the map?
The map scores wind along your route — the headwind and tailwind component in your direction of travel, hour by hour. This page is the same underlying physics for a single steady effort. Use the calculator to understand watts; use the map to find the hour when the wind is actually on your side.
Find your best ever ride with Tailwind GPS
Wind, not watts, is what we are famous for. Use the calculator to understand effort, then plan the ride when the wind is actually with you.