Key Takeaways
- Cycling speed at steady state depends on power output, rider mass, aerodynamic drag (CdA), rolling resistance, road grade, and wind — modeled using the standard Martin et al. cycling power equation.[1]
- On flat terrain above 25 km/h, aerodynamic drag typically accounts for 70–90% of total power — making riding position the single biggest speed lever.[2]
- A 250 W rider on hoods (~CdA 0.35) travels roughly 35 km/h on flat smooth road; switching to aero bars (~CdA 0.24) adds ~2–3 km/h at the same power.[3]
- Each 1% uphill grade increases power demand significantly — a rider sustaining 250 W on flat ground may need 350+ W to hold the same speed on a 5% climb.
How It Works
The calculator uses the steady-state cycling power model:
P = (CdA × ½ρv³ + Crr × m × g × v + m × g × sin(θ) × v) / η
Where P is power (watts), CdA is aerodynamic drag area (m²), ρ is air density, v is speed (m/s), Crr is rolling resistance, m is total mass, g is gravity, θ is road grade, and η is drivetrain efficiency (~97%).
Given power, speed is solved iteratively (Newton-Raphson). Given speed, required power is calculated directly. Headwind increases effective air speed; altitude reduces air density.
For training zone context, pair results with the FTP Calculator and Cycling Power Zones Calculator.
Practical Application
Race pacing: Estimate the power needed to hold a target speed on a known course profile before race day.
Equipment choices: Compare how position changes (hoods vs aero bars) or tire/surface selection affects speed at your FTP.
Indoor trainer setup: Set ERG mode targets based on expected outdoor speeds for your local routes.
Convert ride effort to calories with the Cycling Calories Burned Calculator, or check your relative strength with the Power-to-Weight Calculator.
Accuracy & Limitations
Results assume steady-state riding on a uniform grade with constant wind. Real-world factors not modeled include drafting, acceleration surges, cornering, temperature/humidity effects on air density, and individual CdA variation (±10–15%).
CdA presets are population averages from cycling aerodynamics research.[1] For precise individual CdA, use the Cycling CdA Calculator to estimate or back-calculate from power and speed data.
Advanced Cycling Analysis
For race time predictions on specific courses, try the Cycling Race Predictor. To understand how tire choice affects speed, use the Cycling Rolling Resistance Calculator.
Estimate your Critical Power and W' with the Cycling Watts Calculator. Track ride intensity with the NP & IF Estimator. Optimize tire pressure with the Bike Tire Pressure Calculator.
Frequently Asked Questions
Sources & References
- A Design, Implementation, and Validation of a Power-Predictor for Cycling. Martin JC, Milliken DL, Cobb JE, McFadden KL, Coggan AR. Medicine & Science in Sports & Exercise (1998)
- Power Assessment in Road Cycling: A Narrative Review. Menaspà P et al.. Sports Medicine (2021)
- Power-Speed Profile Performance Model for Road Cycling. Various. ResearchGate (2019)
- Modelling Road Cycling Performance. Various. ScienceDirect (2025)
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This tool is for informational and journaling purposes only.
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