Power - Time Calculator

How the Power-Time Calculator Works

This tool solves a common question every road cyclist and time trialist faces: "How long will it take me to ride this segment at a given wattage?" - or the other way around - "What power do I need to hold to finish in a specific time?"

The calculator uses a physics-based model that balances the power you put into the pedals against the main resistive forces acting on a rider: aerodynamic drag, gravity on the gradient, rolling resistance (Crr) and drivetrain losses. Air density is derived from the altitude and temperature you enter, so high-altitude or hot-weather scenarios produce realistic results.

CdA (drag area) is the single biggest factor on flat and rolling terrain. A typical road cyclist on the hoods sits around 0.32-0.38 m2, while a well-fitted time trial position can drop below 0.25 m2. Even small changes - removing a loose jersey or tucking your elbows - can save minutes over a long course. If you do not know your CdA, the default of 0.30 is a reasonable starting point for a road rider in the drops.

On steep climbs the gradient dominates, and watts per kilogram (W/kg) becomes the metric that matters. The calculator shows VAM (Vertical Ascent rate in Meters per hour) alongside finish time so you can benchmark your result against well-known climbs. For example, a VAM above 1,500 m/h on a sustained climb is world-class.

If you are logged in and have a rider profile with CP and W' set, the tool also estimates your best realistic effort for the segment. FTP is still used as a familiar default power input, while CP and W' drive the best-effort model.