At what altitude does performance drop?

Most riders notice performance loss above 1500m. The effect increases with altitude — at 2500m expect roughly 6-7% power reduction, at 3500m roughly 13-14%.

Does lower air density help with speed?

Yes, lower air density reduces aerodynamic drag, which helps at high speeds. However, the VO2 max reduction usually outweighs the aero benefit except in time trials.

How long does acclimatisation take?

Partial acclimatisation takes 1-2 weeks. Full acclimatisation to a given altitude takes 3-4 weeks. Some performance reduction remains even when fully acclimatised.

Why do teams train at altitude?

Training at altitude (or sleeping in altitude tents) stimulates red blood cell production, which improves oxygen transport when returning to sea level.

BikeCalcs

Altitude Calculator — Altitude Effects on Performance

Calculate altitude effects on cycling performance and power.

Altitude

Sea-Level FTP

How We Calculate This

Altitude Effects

Air density: Decreases with altitude following the barometric formula
Power reduction: ~6.5% per 1000m above 1500m (unacclimatised)
Oxygen: Partial pressure decreases proportionally with barometric pressure

Frequently Asked Questions

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Last updated: February 2026

All calculations are estimates. Always verify results and consult a professional bike fitter where appropriate.