Critical Power Calculator for Runners

Intro

Below we’ve provided a calculator to help you work out your critical power.

The benefit of the High North calculator over other available calculators is that it allows you to input test data from THREE efforts, which helps to improve the model accuracy, and provides an indication of the accuracy of your critical power estimates. However, the calculator also works with just two test efforts. The calculator also allows you to tweak the power for your test efforts to see what effect this has on your critical power estimates, which can be useful if you think you under-paced one of your efforts, for example.

This calculator also allows you to estimate power/duration for short races or efforts lasting 20-mins or less.

If you’d like to learn more about critical pace and power, then we have a full article on this here.

Instructions

  1. To determine your critical power and W’, complete 2-3 maximal efforts, each lasting between 3-mins and 20-mins. We recommend 3-mins, 5-6 mins and 12-mins. You should try to pace these with a consistent power, avoiding a hard start or finish for example.

  2. Find your average power for each effort.

  3. Enter your test data into the calculator below. Be sure to enter the test duration in seconds and not minutes.

  4. Your results will then be automatically calculated. There are two sets of results based on whether you completed two or three tests. Make sure you’re looking at the correct section, depending on how many tests you did.

  5. In the Pacing Calculator section, you can generate estimates of the power you can hold over certain durations, and vice versa. This only works reliably for durations between 3-mins and 20-mins.

Critical Power and W' Calculator

Test 1:
 
Test 2:
 
Test 3:
 
 
Input your test results in this section. Make sure you enter duration in seconds, and not in minutes!

If you only did two tests, then just enter results for Test 1 and Test 2.

Results - Two Test Solution

Critical Power (W):
Approximate FTP (W):
W' (kJ):
If you did two tests, your results will appear in this section. If you did three tests, you should read the results from the next section ('three test solution')

Results - Three Test Solution

Critical Power (W):
Approximate FTP (W):
W' (kJ):
Goodness of Fit (%):
If you did three tests, you should read your results from this section. We ideally want the 'goodness of fit' to be above 97%, which indicates your test efforts were all well-paced.

Pacing Calculator

Use this section to estimate the power you can hold for a given duration and vice versa. This only works for durations between 3-mins and 20-mins (180-1200 seconds). Make sure you look at the appropriate section (two test solution if you did two tests, and three test solution if you did three tests).
Enter Target Duration (s):
Estimated Power (W) (Two-Test Solution)
Estimated Power (W) (Three-Test Solution)
Enter Target Power (W):
Estimated Duration (s) (Two-Test Solution)
Estimated Duration (s) (Three-Test Solution)