b2KIT

Cycling Power Calculator

Estimate watts per kilogram, FTP zones, and power-to-weight ratio for cycling performance.

Tested tool guide Tested browser tools Checked August 16, 2026

What Cycling Power Calculator does and how it behaves

Relate a cyclist's power output to body mass and turn an FTP value into watt-based training ranges. The calculator divides watts by rider mass in kilograms for the power-to-weight figure, then applies percentage bands to FTP for the zone table. The main trap is comparing unlike efforts: 350 watts for a short sprint and 250 watts sustained near threshold describe different abilities, even after both are expressed in watts per kilogram.

How the result is produced

1

Power-to-weight calculation

Power-to-weight ratio is power in watts divided by rider mass in kilograms. A result in W/kg therefore belongs to the particular power value entered, such as FTP, a five-minute best, or sprint power. The ratio makes riders of different masses easier to compare for the same effort duration, but it does not convert power into road speed.

2

FTP zone ranges

The zone section treats FTP as the reference value and expresses training intensities as watt ranges around it. Each boundary is obtained from a percentage of FTP and may be displayed as a whole-watt value. Zone systems do not all use identical names or boundaries, so the calculator's displayed ranges should be used together rather than mixed with labels from another system.

Good uses

  • Convert a measured FTP and current body mass into FTP watts per kilogram before comparing climbing fitness across training blocks.
  • Prepare watt targets for an indoor cycling workout whose intervals are prescribed by FTP zone.
  • Compare two power efforts of the same duration while accounting for a change in rider mass.

Limits and checks

  • Confirm that body mass is expressed in kilograms before interpreting W/kg; confusing pounds with kilograms produces a substantially incorrect ratio.
  • Match the effort duration when comparing riders or past results. Five-minute W/kg is not interchangeable with FTP W/kg.
  • Treat zone boundaries as training guidance, not exact physiological transitions. FTP measurement error and day-to-day condition affect every derived range.

Common questions

Should I use average ride power or FTP for the power entry?

Use FTP when the question is threshold power-to-weight or FTP training zones. Average power from an entire ride usually includes descending, coasting, stops, and varied intensity, so it does not represent FTP. For another comparison, such as five-minute W/kg, enter the power from that duration and label the result accordingly.

Does a higher watts-per-kilogram result always mean I will ride faster?

No. W/kg is especially informative when gravity is a major resistance, such as on sustained climbs. On flatter roads, absolute power, aerodynamic drag, rolling resistance, wind, drafting, and riding position can matter more. The calculator describes the relationship between power and mass; it does not predict speed or finishing time.

References and verification

The behavioral notes were checked against the browser implementation. Standards and primary references below define the relevant format, formula, or platform behavior.

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