Bike Calculator

Bike Power & Speed Calculator: Convert Watts ↔ km/h / mph

Calculate your cycling speed from power (watts) — or estimate the watts required for a target speed in km/h or mph. Ideal for road cycling, time trials, and triathlon.

This calculator combines aerodynamics (CdA), rolling resistance (Crr), gradient, total system weight, air density, and drivetrain efficiency. It lets you compare position, tires, equipment, and pacing far more realistically than basic average-speed calculators.

Watts → km/h Watts → mph km/h → Watts mph → Watts Built for Time Trial & Triathlon
Triathlon Focus: Use this tool to compare sprint, Olympic, 70.3, and Ironman scenarios across position, tires, weight, course profile, and target pace — before you go out too hard on race day.

Run Calculator

Choose calculation mode, units, and setup.

Why this matters for time trialing and triathlon

Evaluate aero decisions

Compare whether a more aggressive position, an aero helmet, or faster tires will save you more time on your course than simply reducing weight.

Plan your pacing before race day

Test target speeds ahead of time instead of getting pulled into overly optimistic averages during the race.

Understand system weight impact

Understand when weight starts to matter — and when aerodynamics still dominates on flat or rolling terrain.

Balance bike split vs. run performance

In triathlon, it’s not just about a fast bike split — it’s about a sustainable one. This tool helps you understand the real physical limits.

Simple oder Expert – welcher Modus ist wann sinnvoll?

Simple Mode

Ideal for quick comparisons between power, speed, weight, position, and road surface — perfect for a fast reality check before training or racing.

Expert Mode

For more precise simulations including air density, elevation, temperature, air pressure, and drivetrain efficiency. Designed for serious time trialists and data-driven triathletes.

Race Interpretation

Don’t use the calculator in isolation: the best setup always depends on course profile, wind, race duration, and your ability to hold your position under fatigue.

What actually determines your speed?

Aerodynamics (CdA)

On flat terrain, aerodynamics is almost always the dominant factor. Small improvements in position and frontal area matter more as speed increases.

Rolling Resistance (cr)

Tires, casing, pressure, and road surface all continuously cost power. This factor is often underestimated in triathlon and time trial setups.

Gradient & System Weight

The steeper the course, the more weight and watts/kg matter. On flat courses, aerodynamics usually outweighs saving a small amount of weight.

Air Density & Drivetrain

Temperature, altitude, air pressure, and drivetrain condition all affect real power at the wheel. For serious comparisons, include these in Expert mode.

Next step: from calculator to race-specific simulation
If you want to go beyond averages and make real race decisions, open race-specific pages with course preview, map, and simulation.
Open race-specific bike pacing simulations Open CdA & Crr Converter

FAQ: Power & speed calculator

It depends mainly on CdA, rolling resistance, total system weight, course, and air density. On flat terrain, aerodynamics is usually the biggest factor — meaning the same speed can require very different power depending on position and equipment.

250 watts can result in very different speeds depending on rider size, position, tires, terrain, wind, and gradient. That’s why a physics-based calculator is more useful than generic tables.

In most flat and fast scenarios, aerodynamics matters more than weight. As the course gets steeper, total system weight becomes increasingly important.

Yes. It’s especially valuable for triathlon and time trials, where position, aero equipment, rolling resistance, and sustainable pacing have a major impact on your bike split.

It’s very useful for comparisons and setup decisions, but real-world factors like wind, road surface, and your ability to hold position under fatigue will also affect actual results.