Critical Power test guide: calculate CP, W′ and training zones

Follow this step-by-step guide to calculate your Critical Power (CP) and W′ using the Critical Power calculator after completing your testing. You will also learn how to generate your SEMIPRO Power training zones and enter them into TrainingPeaks.

Before you start

You need two recent max efforts: one in the 3–5 minute range, and one in the 12–20 minute range. The 1-day test protocol is in every SEMIPRO plan. If you have not tested yet, do the protocol first. These efforts feed the calculator.

Step 1: Open the calculator

Go to the Critical Power calculator. Enter duration in seconds and average power in watts for each effort. The calculator accepts two efforts, with an optional third.

Step 2: Enter your numbers

Enter the duration and average power of each effort. The calculator returns your Critical Power (CP) in watts and your W′ (W prime) in kilojoules. These estimates describe part of your power profile. They do not measure every aspect of fitness or replace reviewing your training response.

Step 3: Get your SEMIPRO Power zones

The calculator outputs these SEMIPRO Power ranges from your estimated CP. Treat them as initial coaching targets, not individually measured physiological boundaries:

• Recovery · 40–54% of CP, light aerobic and effortless
• Endurance · 55–74% of CP, steady and conversational
• Tempo · 75–89% of CP, moderate and just below threshold
• Threshold · 90–105% of CP, hard sustained

Step 4: Enter them in TrainingPeaks

In TrainingPeaks, open Settings → Zones → Power. Select SEMIPRO Power as the zone scheme (or create a custom zone set named that way) and enter each zone's wattage range from the calculator output. Save.

When to retest

Every 6–8 weeks of consistent training, or any time sessions feel meaningfully easier or harder than the prescribed effort. Retesting too often leads to noisy numbers; not often enough leaves you riding with stale targets.

Check your result before using the zones

• Use average power for each complete effort, not peak or Normalized Power.
• Enter duration in seconds: 3 minutes is 180 seconds and 12 minutes is 720 seconds. Use recent efforts from comparable testing conditions.
• If either effort was not maximal, treat the result cautiously. A two-point estimate cannot show how well additional efforts fit the model.

Read Critical Power versus FTP before substituting one number for the other. The cycling training-zones guide explains how to interpret the targets.

Turn the test into a training decision

If you want help reviewing your results and choosing what to work on next, compare SEMIPRO’s online cycling coaching options.