Critical Power Calculator Guide: Estimate Cycling CP and W Prime From Field Tests
Use a critical power calculator to estimate CP and W Prime from 3-minute and 12-minute efforts, then apply critical power to VO2 max, anaerobic, and race-specific training.
A critical power calculator estimates cycling CP and W prime from hard efforts such as 3-minute and 12-minute tests. If you searched for "critical power calculator", "CP calculator cycling", "W prime calculator", or "3 minute 12 minute critical power", you are looking for a performance model that goes beyond FTP.
Critical Power is useful for athletes who care about repeatability, short-duration power, threshold-like durability, and race demands above threshold. The TrainingDojo calculator gives a practical estimate from field-test data.
Open the free critical power calculator and use the result as the starting point for the training decisions below.
The Problem: FTP Does Not Explain Every Effort
FTP is a strong training anchor, but it does not fully describe how you handle work above threshold. Two riders can have similar FTP and very different ability to surge, attack, climb short hills, or repeat anaerobic efforts.
Critical Power and W prime help describe that relationship. CP approximates the boundary between heavy and severe intensity. W prime represents a finite work capacity above CP.
What the critical power calculator Gives You
- Estimated Critical Power from maximal field-test efforts.
- Estimated W prime when inputs support it.
- A useful benchmark for VO2 max, anaerobic, and race-specific training.
- A bridge from raw test efforts into a training block.
How to Use the Calculator
- Use maximal efforts that are recent, well-paced, and separated enough to be valid.
- Enter the 3-minute and 12-minute powers from the test protocol.
- Read CP and W prime together instead of treating CP as another FTP label.
- Retest after a focused training block or race season change.
Common Mistakes to Avoid
- Using casual ride segments instead of true maximal efforts.
- Testing while fatigued and underestimating CP.
- Comparing CP directly to FTP without understanding the model difference.
- Ignoring repeatability, recovery, and event specificity.
Turn the Number Into Training
Critical Power can guide workouts that FTP alone does not describe well: VO2 max intervals, over-unders, anaerobic capacity work, race surges, and hard starts.
Use the calculator to understand your current profile, then use TrainingDojo to build a CP-aware training block that targets the weakness that matters for your event.