What is CdA in cycling?

CdA is the product of drag coefficient (Cd) and frontal area (A). It represents your aerodynamic drag. A typical road cyclist in the drops has a CdA around 0.32–0.36 m². Aero positions or TT bikes can bring it below 0.25 m².

What is a good watts per kilogram (w/kg) for cycling?

W/kg benchmarks vary by duration. For FTP (1-hour power): under 2.0 is untrained, 2.0–3.0 is recreational, 3.0–4.0 is trained/sport, 4.0–5.0 is competitive/cat 3-4, above 5.0 is elite/pro. These are approximate guidelines, not fixed categories.

How accurate is this calculator?

The model uses standard equations for aerodynamic drag, rolling resistance, and gravitational force. Accuracy depends on how well your inputs match reality. CdA and Crr vary with position, tire pressure, and surface. Expect ±5–15% of a power meter reading under typical road conditions.

What rolling resistance (Crr) value should I use?

Typical values: 0.005 for high-end road tires on smooth asphalt, 0.006–0.008 for average road tires, 0.010–0.015 for gravel or rough surfaces. The default 0.005 suits most road cycling scenarios.

What air density should I enter?

At sea level and 20°C, air density is about 1.225 kg/m³. At 1,500 m altitude it drops to roughly 1.06 kg/m³. Higher altitude or temperature means less air resistance and lower required power for the same speed.

What are cycling training zones?

Training zones classify effort by percentage of FTP (Functional Threshold Power). Zone 1 is active recovery, Zone 2 is endurance, Zone 3 is tempo, Zone 4 is threshold, Zone 5 is VO2 max, and Zone 6+ is anaerobic/neuromuscular. This calculator uses the common 6-zone model.

Cycling Power Calculator

Enter your speed, weight, gradient, and CdA to estimate cycling power output in watts and w/kg for training zone reference.

Inputs

Unit System

Speed (km/h)

Rider + Bike Weight (kg)

Rider Weight Only (kg) for w/kg

Road Gradient (%)

Your FTP (watts) for zone reference

Fill in the inputs on the left and click Calculate Power

Watts • W/kg • Training Zone • Power breakdown

Estimated Power Output

— W

Total Power

watts

W/kg

watts / kg

Speed

km/h • mph

Power Breakdown

Component	Watts	Share

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Summary

This cycling power calculator estimates the watts needed to maintain a given speed based on physics: aerodynamic drag, rolling resistance, and gradient. Enter your speed, total weight, road slope, and optional aerodynamic parameters to get an instant power estimate. The tool also computes your watts per kilogram and maps the result to a standard training zone for structured workout planning.

How it works

Enter your cycling speed in km/h or mph.
Input the combined weight of rider and bike in kg or lb.
Set the road gradient as a percentage (negative for downhill).
Optionally adjust CdA (drag area) and rolling resistance for more accuracy.
Click Calculate to see estimated power in watts, watts per kilogram, and your training zone.
Use the Reset button to clear all fields and start over.

Use cases

Estimate the power required to ride a specific segment at a target speed.
Find your watts per kilogram to benchmark fitness against cycling categories.
Plan a climb by entering the gradient and your target speed to see required power.
Compare the effect of weight loss or weight savings on power demand.
Identify which training zone a given effort falls into for workout planning.
Check how much aero improvement (lower CdA) reduces required power at race speed.

Frequently Asked Questions

Last updated: 2026-06-13 · Reviewed by Nham Vu