Cycling power zones calculator

• Z1 Active recovery, under 55%. Spinning. Used to move blood, not to build anything.
• Z2 Endurance, 56–75%. Conversational. Boring, unglamorous, and the single biggest driver of aerobic fitness. Most hours in any sane plan sit here.
• Z3 Tempo, 76–90%. Comfortably hard. Useful, and easy to overuse — tempo every day is how riders end up permanently tired and never fast.
• Z4 Threshold, 91–105%. No talking. This is the work that moves FTP directly, in blocks of 8 to 20 minutes.
• Z5 VO₂max, 106–120%. Three to five minutes at a time. Very effective, very expensive in recovery.
• Z6–Z7, above 120%. Anaerobic and sprint work. Rarely needed by anyone training for distance rather than racing.

Sweet spot is not a numbered zone — it is the 88–94% band straddling Z3 and Z4, and it is the backbone of most time-limited plans, including mine: hard enough to build the engine, easy enough to repeat twice a week.

Because then one new test number rewrites the entire plan at once. Every session on this site is stored as a percentage of FTP, which is also why the free Zwift files work for anyone — Zwift applies your FTP, not mine, so the targets land where they should without anything being converted.

It also means your zones are only as good as your FTP number. If the last test was two months and five kilograms ago, re-test before trusting these watts.