What is a good W/kg for cycling?

For recreational cyclists, 2.0-3.0 W/kg is typical. Competitive amateur racers are usually 3.5-4.5 W/kg. Pro Tour cyclists sustain 5.5-6.5 W/kg for an hour.

How does aerodynamic drag affect cycling power?

Aerodynamic drag increases with the cube of speed. At 40 km/h on flat ground, aero drag accounts for roughly 80% of total power demand. Reducing CdA through position changes can save 20-50 watts.

What is CdA in cycling?

CdA (coefficient of drag times frontal area) measures overall aerodynamic resistance. Road cyclists on hoods typically have CdA of 0.35-0.40 m2, while TT positions can achieve 0.22-0.26 m2.

Cycling Power Calculator

Full physics model: power breakdown by gravity, rolling resistance & aero drag. Terrain analysis & race predictions.

Rider & Conditions

FTP / Power (W)

Body Weight

Bike Weight (kg)

Speed (km/h)

Gradient (%)

Headwind (km/h)

Aerodynamics

CdA (m²)

Crr (rolling)

Power Analysis

— W/kg

—

FTP—

Weight—

Est. Speed—

VAM (m/hr)—

Calories/hr—

Total Power—

Gravity—

Rolling—

Aero Drag—

P = P_grav + P_roll + P_aero + P_drive

P_aero = 0.5 · ρ · CdA · v³

Power Breakdown at Current Speed

Where You Stand

Terrain Parameters

Gradient (%)

Distance (km)

Rider Weight (kg)

Target Speed (km/h)

Terrain Results

Power Required—

VAM (m/hr)—

Est. Time—

Elevation Gain—

Gradient Comparison

Terrain	Power	Elev. Gain	VAM

Power vs Gradient Curve

Your Race Profile

FTP (watts)

Race Distance (km)

Elevation Gain (m)

Rider Weight (kg)

CdA (m²)

CdA Estimation Helper

Height (cm)

Riding Position

Estimated CdA Range —

Your Custom Race

Common Race Profiles

Estimated Race Times Comparison

How to Use This Calculator

Enter your power and weight — Input your FTP (Functional Threshold Power), body weight, and bike weight. Adjust speed, gradient, and wind conditions.

Fine-tune aerodynamics — Select a riding position preset or enter a custom CdA. Adjust rolling resistance (Crr) for your tire type.

Explore terrain effects — Switch to the Terrain Analysis tab to see how power demands change across gradients from -5% to +15%.

Predict race times — Use the Race Predictor to estimate finish times for common race profiles or your custom event.

Key Terms

W/kg — Watts per kilogram; the standard metric for comparing cycling fitness across body sizes.

CdA — Coefficient of drag times frontal area (m²). The single number that captures your total aerodynamic resistance.

Crr — Coefficient of rolling resistance. Road tires are ~0.004–0.006; MTB tires ~0.008–0.012.

VAM — Velocità Ascensionale Media (vertical ascent metres per hour). Elite climbers sustain 1500–1700 VAM.

FTP — Functional Threshold Power; maximum sustainable power for ~60 minutes.

Drivetrain Loss — Typically 2–4% of total power lost to chain, bearings, and gear friction.

Real-World Examples

Flat TT at 40 km/h
75kg rider, CdA 0.24: needs ~280W — 80% is aero drag. Dropping from hoods (0.38) to TT bars saves ~90W at the same speed.

Alpe d'Huez Climb
8% gradient, 13.8km: a 70kg rider at 5.5 W/kg (385W) climbs in ~42 minutes. Gravity accounts for 85% of power demand.

Gran Fondo
160km with 2500m climbing: at 72% FTP (180W for 250W FTP), expect ~5h 30m finish time for a 75kg rider.

Understanding Cycling Power Dynamics

Cycling power is governed by four resistance forces: gravity, rolling resistance, aerodynamic drag, and drivetrain friction. The relative importance of each depends entirely on the riding conditions. On steep climbs, gravity dominates (70–90% of total power). On flat roads at speed, aerodynamic drag accounts for 80–90% of power demand.

The CdA Revolution

CdA (coefficient of drag times frontal area) has become the most important metric in time trialing and flat-road racing. A typical road cyclist on the hoods has a CdA of about 0.35–0.40 m². Moving to the drops reduces this to 0.30–0.35. A dedicated TT position achieves 0.22–0.26. Because aerodynamic drag increases with the cube of speed, these reductions translate to massive power savings at race speeds.

Terrain Strategy

Smart pacing on varied terrain is crucial. On climbs, power-to-weight ratio determines speed. On descents and flats, absolute power and aerodynamics matter most. The Terrain Analysis tab lets you see exactly how power demands change across gradients, helping you plan interval efforts and race pacing strategies.

Race Duration and Sustainable Power

No rider can sustain FTP for more than about an hour. For longer events, sustainable power drops: roughly 88% of FTP for 2 hours, 78% for 4 hours, and 70% for 6+ hours. The Race Predictor factors this duration-power relationship into its estimates, giving realistic finish time predictions.

Frequently Asked Questions

What is a good W/kg for a recreational cyclist?

For recreational cyclists, 2.0–3.0 W/kg is typical. Completing a gran fondo or sportive comfortably usually requires around 2.5–3.0 W/kg sustained over several hours.

How does aerodynamic drag scale with speed?

Aerodynamic power increases with the cube of speed. Doubling your speed requires 8x the aerodynamic power. This is why at 40+ km/h, reducing CdA by even 0.01 m² can save 3–5 watts.

What CdA should I use for my riding position?

Upright/MTB: 0.45–0.55. Road bike hoods: 0.35–0.40. Road bike drops: 0.30–0.35. Aero tuck: 0.25–0.30. TT position: 0.22–0.26. The CdA Estimation Helper in the Race Predictor tab can provide a starting estimate based on your height.

Does W/kg matter for flat cycling?

On flat roads, aerodynamics and absolute power dominate. A heavier rider can produce more absolute watts and maintain higher flat speeds. W/kg becomes critical on any climb above about 3% gradient.

What is VAM and why is it useful?

VAM (vertical ascent metres per hour) measures climbing speed in a gradient-independent way. Elite climbers sustain 1500–1700 VAM on Tour de France climbs. It allows comparison across different gradients and distances.

How do I test my FTP?

The standard 20-minute test: after a warm-up, ride as hard as possible for 20 minutes. Multiply average power by 0.95 for FTP. Alternatively, use a ramp test or 60-minute all-out effort.

Why does the Race Predictor use different FTP percentages?

FTP represents ~1-hour power. For shorter events (criteriums), you can exceed FTP. For longer events, sustainable power drops: 88% for 2hr, 78% for 4hr, 70% for 6+hr. The predictor adjusts automatically based on expected duration.

What rolling resistance (Crr) should I use?

Slick road tires at high pressure: 0.003–0.005. Standard road tires: 0.005–0.007. Gravel tires: 0.006–0.010. MTB tires on dirt: 0.010–0.015. At 30 km/h, reducing Crr from 0.005 to 0.003 saves about 5–8 watts.

How accurate are the power estimates?

The physics model is well-established and used by professional cycling teams. Accuracy depends on input quality: CdA is the hardest to measure precisely. Real-world conditions (wind gusts, road surface, drafting) add variability. Estimates are typically within 5–10% of actual measured power.

What W/kg did Tour de France winners average on climbs?

Modern Tour de France winners climb major cols at approximately 5.8–6.2 W/kg for extended efforts. The legendary performances on Alpe d'Huez suggest 6.5–7.0 W/kg for shorter burst efforts.