SuperPower Calculator

The SuperPower Calculator (SPC) contains a comprehensive suite of calculators and converters useful to anyone training, racing, and running with power.

Some of the more common features include:

  • Adjusting power based on altitude, temperature, and humidity.
  • Calculating race target power.
  • Calculating FTP/CP.

Other features include:

  • Calculating power metrics (RE, horizontal power ratio, LSS/kg, CVI) from activities.
  • Calculating what increase in FTP/CP is necessary to achieve a specific time.
  • Calculating predicted race time.
  • Working with and calculating zones from FTP/CP.
  • Calculating or looking up a Riegel exponent (i.e. fatigue factor).

Getting Started

SuperPower Calculator requires a Google Account. If you don’t have one, please create one beforehand.

Note: During sign up, you can use an existing email address as a Google Account. Creating a separate Gmail email address isn’t required.

Step 1: Make a Copy

Make sure you’re signed into your Google Account and then open the SuperPower Calculator (SPC). It will prompt you to make a copy.

Since the SPC is updated periodically, it’s a good idea to make a copy regularly using that link to ensure you’re using the latest version.

Step 2: Choose a Calculation

At the top of the MAIN sheet, click the arrow in the yellow cell under the What do you want to do (Calculation) cell.

In the dropdown that appears, choose a calculation.

Step 3: Follow the Instructions in the Next Steps Section

Depending on the calculation, some of the sections below will be displayed. Fill out all required and optional (where appropriate) fields listed in each section.

Yellow cells are required. Blue cells are optional.

  • Basic Data: Fields used for most calculations.
  • Additional Inputs: Additional fields used in the chosen calculation.
  • Environment Adjustments: SPC can apply environment adjustments (altitude, temperature, and humidity) to almost all calculations. The field names will change to provide more context depending on the selected calculation.
  • Results: Shows the results for the chosen calculation. Green cells are the results.
  • Activities Tab: Used in calculations requiring multiple previous activities.
  • Scenarios Tab: Used for calculating race target power based on different RE and Riegel pairs.
  • Zones Tab: Used for various P3 zone calculations.
  • Riegels Tab: Used to lookup a Riegel exponent using a previous race distance and time.
  • Charts: For some calculations, results are graphed in this tab.

Supported Calculations

Altitude, Temperature, and Humidity

  • Adjust Power (or FTP/CP) based on Altitude/Temperature/Humidity

To adjust FTP/CP based on environment, choose FTP/CP as the unit of measure for the Power field.

Race Target Power

  • Calculate Race Target Power using FTP/CP, Target Time and Riegel Exponent
  • Calculate Race Target Power from a Prior Race, Target Time and Riegel Exponent
  • Calculate Race Target Power from a Prior Race, Target Distance and Riegel Exponent
  • Generate Race Target Power Scenarios using pairs of Riegel Exponents and RE
  • Calculate Race Target Power using Target Distance, Time and Running Effectiveness


  • Calculate FTP/CP (and AWC if possible) from a Prior Race Power/Time and Riegel Exponent
  • Calculate FTP/CP and AWC from 2 or more maximal effort Activities

The calculation using 2 or more maximal efforts should only be used with short to medium-duration activities between 2 and 20 minutes as commonly seen with 9/3 minute, 6/3 lap, or 3/10 minute CP tests. It should not be used with race data.

See Using the Activities Tab for more information on ensuring valid and accurate calculations.


  • Calculate Power metrics (RE, HPR, LSS/kg, CVI) for up to 10 completed Activities
  • Given my current FTP/CP, what FTP/CP % improvement do I need to break y:yy?
  • Calculate Zones from FTP/CP; Lookup specific %FTP or Wattages; Calculate Zone.Decimals
  • Calculate Predicted Race Time using Target Distance, Power and Running Effectiveness
  • Lookup Riegel Exponent using a Prior Race Distance/Time and a Target Distance
  • Advanced: Calculate Riegel Exponent using up to 10 completed Activities (and optionally FTP/CP)

Key Concepts


In simple terms, it represents your current fitness and is measured in watts (W) or watts per kilogram (W/kg).

Functional threshold power (FTP) and critical power (CP) can be used interchangeably in a running context. So where you see FTP used, CP can be used or vice versa.

Further Reading: What is Critical Power (CP)?

Time to Exhaustion (TTE)

TTE measures how long a person can maintain their FTP/CP before fatiguing. It can vary greatly from runner to runner (e.g. 30-75 minutes). If you don’t know your TTE, power-based calculations use 50 minutes as the default.

Despite 50 minutes not being accurate for all runners, the difference is small enough to not significantly impact power targets.

Further ReadingRunning Functional Threshold Power – A Primer.

Running Effectiveness (RE)

Not to be confused with running economy or running efficiency, running effectiveness measures how effective a runner is at converting power to speed.

RE’s utility is primarily found in race planning and post-run analysis.

Further Reading: What is Running Effectiveness (RE)?

Riegel Exponent (Fatigue Factor)

A runner’s fatigue factor can help predict finish times based on a known race time or critical power. It measures how much a runner fatigues over increased distances and is a key part of good race power planning.

Assume two runners with identical 5k PRs run the same marathon. Everything else equal, the runner with the lower fatigue factor will have the faster marathon time.

In other words, the lower the fatigue factor, the less a runner will slow down over increased distances.

Further Reading: What is a Fatigue Factor (i.e. Riegel Exponent)?

For calculations requiring a Riegel exponent, there are a few different approaches:

  1. If known, specifying a Riegel exponent directly.
  2. Use the Lookup Riegel feature.
  3. Use the Advanced: Calculate Riegel Exponent using up to 10 completed Activities (and optionally FTP/CP) calculation.

For most users, Option #2 is recommended. It can be done in two different ways:

  1. Choose Lookup Riegel Exponent using a Prior Race Distance/Time and a Target Distance from the calculation dropdown.
Lookup Riegel Exponent using a Prior Race Distance/Time and a Target Distance - SuperPower Calculator
  1. Select the Lookup Riegel option from the dropdown in any calculation requiring a Riegel exponent.
Lookup Riegel From Calculation - SuperPower Calculator

Depending on the calculation, you will need to specify other required fields.

When using Option #3, please make note of the following:

  • See Using the Activities Tab for more information on ensuring valid and accurate calculations.
  • To calculate a Riegel Exponent using FTP/CP, choose TRUE in the row labeled Include FTP/CP and TTE? at the bottom of the Activities tab.
Inclut FTP/CP and TTE? - SuperPower Calculator

Altitude, Temperature, and Humidity (Environmental Conditions)

Environmental conditions (e.g. altitude, temperature, and humidity) impact an athlete’s ability to generate and maintain specific power levels. For example, running at 100% FTP is significantly easier under cool conditions versus hot, humid conditions at a higher altitude.

SPC incorporates Stryd’s Race Power Predictor to normalize activities taking place in different environments (i.e. a race with conditions different than your typical training environment).

This ensures proper effort is targeted under different conditions.

Using the Activities Tab

For calculations requiring the Activities tab, you may see a warning in the Results section of the MAIN tab.

The warning is shown when the calculation can’t produce a result or produces an inaccurate one (using linear regression).

For more accurate results, make sure you follow these guidelines:

  1. Activities should have varied durations. Using similar durations will over or underestimate results.
  2. Activities should be maximal (or near maximal) efforts. Sub-maximal efforts will underestimate results.
  3. When calculating a Riegel exponent, at least one of the activities should be a similar distance to the planned race distance. If one isn’t available, use one as close as possible. For a marathon, even a 10k activity would produce much better results than activities at shorter distances.

Walkthrough Videos


SuperPower Calculator is a collaboration between:

With kind permission from the Stryd Team to incorporate their altitude, temperature, and humidity power converter.