Power in. Speed out. Pure physics.
Type your sustainable power, total weight, gradient, surface and position. We solve the cycling power equation and tell you exactly how fast that watt number is.
Three forces consume your watts: rolling resistance (Crr × m × g × cos θ × v), aerodynamic drag (½ × ρ × CdA × v³) and gravity on a slope (m × g × sin θ × v). Aero drag scales with the cube of speed — going from 35 to 40 km/h costs roughly 50% more watts to overcome. On flat roads above 30 km/h, drag dominates: 80% of your power fights the air. Climbing inverts this — gravity dominates above 5% and CdA barely matters.
Aero position gives the biggest free speed for non-climbing rides — moving from hoods (CdA 0.36) to drops (0.31) at 250 W is roughly +1 km/h on flat road, and TT bars (0.22) add +2.5 km/h. Tyres matter too: a 28 mm GP5000 (Crr ~0.0035) saves 12 W vs an everyday training tyre (Crr ~0.0060) at 35 km/h. On climbs steeper than 5%, weight beats aerodynamics — every kg saved buys real time. Set the air-density override at altitude (Mt Ventoux summit air is ~25% thinner than sea level).
この計算機とよく組み合わせて使うツール — 新しいタブで開いて計画を続けよう。
Estimate your FTP from a 20-minute test and get all 7 Coggan power zones. The cycling-training gold standard.
Convert pace, finish time and distance for any race from 5K to ultra. Includes split times and predicted race times.
Type a recent race result and we predict your finish time at every standard distance — 5K, 10K, half marathon, marathon and beyond.
Combine your 1km run pace with station times to predict your HYROX finish — Pro, Open, Men, Women.
On flat roads, ~80% of your power fights aerodynamic drag, which scales with v³. On a 6% climb, gravity dominates: lifting your mass against the slope eats most of the watts and aero drag becomes a small fraction of the total. The same 250 W gives ~37 km/h on flat road and only ~12 km/h on a 6% climb.
A lot. Going from sitting up (CdA ~0.45) to hoods (0.36) is +2 km/h at 200 W on flat. Hoods to drops is +1 km/h. Drops to clip-on aero bars is +1.5 km/h. A full TT setup (CdA 0.22) is +4 to +5 km/h vs hoods at the same wattage. Aerodynamics is the cheapest free speed in cycling.
No — this calculates your solo speed at the given power. Drafting in a paceline cuts the power required at a given speed by 20–30% for the second wheel, more for deeper positions. To model drafting, drop your effective CdA by 20–30% (e.g. 0.31 → 0.22 in a peloton).
Rider + bike + bottles. The full system mass is what gravity acts on when climbing and what rolling resistance scales with. A 70 kg rider on a 7 kg WorldTour bike with 1 kg of fluid weighs 78 kg; a 70 kg rider on a 12 kg endurance bike with 1.5 kg of fluid weighs 83.5 kg.
Aero drag scales linearly with air density (ρ). At sea level, ρ = 1.225 kg/m³. At 2 000 m altitude, ρ ≈ 1.05 — so any given speed is ~14% cheaper aerodynamically. This is why hour records and TT world records are set at altitude. Heat also reduces ρ slightly (warm air is less dense).
Within 1–2% on a steady effort. We use the same physics. Real-world rides are messier: wind direction, road surface variation, uphill/downhill recovery and pacing strategy all add noise. Use this as a planning tool — what watts are needed for a target time, what position to choose, what gear ratio to fit.