Critical Power (CP) Calculator
Informational calculator for rowing logs and planning. Build CP and W Prime estimates from test efforts and review model-based pace projections.
Critical Power Inputs
Enter two or three efforts from your recent rowing log.
Calculation Method
Test 1 (Short Effort)
Test 2 (Medium Effort)
3-minute max
3:00 - ~750-900m
7-minute max
7:00 - ~1800-2100m
12-minute max
12:00 - ~3000-3500m
Critical Power Estimate
263W
Split at CP: 01:50.0/500m
W Prime Estimate
Model work reserve
FTP Proxy
0.95 x CP estimate
Split at CP
/500m
Power-Duration Curve
The hyperbola shows predicted sustainable power at each duration. Your test points are overlaid.
Above-CP Time Estimates
Estimated finite duration for selected powers above CP:
Planning Power Ranges
Simple CP-based ranges for session logging and planning notes:
Race Pace Projections (Model-Based)
Projection solver combines the Concept2 pace-power conversion with your CP + W Prime estimate.
1,000m
1k
2,000m
2k
5,000m
5k
6,000m
6k
10,000m
10k
21,097m
Half Marathon
Critical Power Planning Notes
This page is designed for training logs and planning. It calculates CP and W Prime estimates from your entered efforts and provides model-based pace projections across common rowing distances.
Model Formula
CP is the slope of work vs. time, and W Prime is the intercept. These values are estimates from the inputs you provide.
Projection Logic
For each target distance, the calculator solves for time where required rowing power equals modeled power:
Confidence labels are based on target-to-input distance ratio: High (0.5x to 2x), Medium (0.25x to 4x), Low (outside that range).
FAQ
How often should I update entries?
Many users update every 4-8 weeks or after a clear change in recent session results.
Can I use race pieces instead of dedicated tests?
Yes. Recent hard efforts from your log can be used, as long as durations are distinct enough for the model fit.
Why are there confidence labels?
Confidence drops as projections move farther from your input distance range.
Is FTP a direct measurement here?
No. The FTP value is shown as a proxy estimate using 0.95 x CP.
References
- Monod H, Scherrer J. (1965). The Work Capacity of a Synergic Muscular Group.
- Poole DC, Burnley M, Vanhatalo A, Rossiter HB, Jones AM. (2016). Critical Power.
- Clark IE, et al. (2021). Critical Power and the power-duration relationship in endurance performance.
- Discussion of practical time limits around CP in validation contexts.
- Concept2 pace-power conversion reference.
Using CP and W'
CP is ideal for pacing strategy: any effort above CP depletes W' at a predictable rate. For a 2K race, knowing your CP and W' tells you exactly how much "above threshold" effort you can afford. CP is similar to FTP but derived from a mathematical model rather than a single-duration test, making it potentially more robust.
What Is the Critical Power Model?
The critical power model splits your exercise capacity into two components. Critical Power (CP) is the highest power you can theoretically sustain indefinitely — it represents your aerobic ceiling. W' (pronounced “W prime”) is a finite energy reserve above CP, measured in kilojoules (kJ), that is depleted whenever you exceed CP and replenished whenever you work below it.
Together, these two parameters can predict performance at any duration: Time to exhaustion at a given power = W' / (Power − CP). This means a rower with CP of 250W and W' of 20kJ can sustain 300W for exactly 400 seconds (20,000 / 50). The model requires at least two efforts of different durations to solve for both unknowns — typically a short effort (1–3 minutes) and a long effort (7–20 minutes).
CP vs. FTP: When to Use Each
FTP (Functional Threshold Power) is a single-test estimate of threshold power, typically 95% of 20-minute average power. CP is a model-derived value that requires multiple test efforts but provides both a threshold estimate (CP) and an anaerobic capacity metric (W'). CP tends to be slightly lower than FTP because it represents a true mathematical asymptote rather than a practical test estimate. For training zone calculation, either works well. For race pacing, the CP model is superior because it explicitly accounts for anaerobic reserves.
Applying CP to Race Pacing
In a 2K race, you will spend the entire race above CP, depleting your W' reserve. The optimal strategy distributes W' evenly across the race duration with a slight reserve for the sprint finish. If you start too hard and deplete W' early, you will be forced to row at or below CP for the remainder — resulting in a dramatic slowdown. Use our 2K Race Plan Calculator to build a pacing strategy informed by your CP data.
Model details: Methodology.
Related Tools
- FTP Calculator — alternative threshold estimation
- Power Curve — visualize your full power-duration profile
- Split Predictor — predict race times from CP data
Standards & Guides
- 2000m Rowing Standards — benchmark your 2K performance
- 5000m Rowing Standards — endurance benchmarks by age
- Training Zones Explained — apply CP to structured training