Coggan IF/TSS Normalized Power Calculator

Compute fourth-power time-weighted NP/IF/TSS from caller already 30-second-rolling power observations; no invented raw-series smoothing or acute readiness/injury score.

Description

Normalized Power weights rolling power to the fourth power.

Normalized Power weights rolling power to the fourth power. Intensity Factor and Training Stress Score (TSS) then compare that result with measured functional threshold power (FTP) and represented duration.^{[1, 2]}

The returned values include Normalized power watts, Intensity factor, Modeled training stress score. The How section below explains the calculation, input rules and interpretation.

When to use Coggan IF/TSS Normalized Power Calculator

Use Coggan IF/TSS Normalized Power Calculator when you need to evaluate the supplied records under the calculation and evidence rules below. No raw-series smoothing, readiness, injury prediction or exercise clearance is performed.

Prepare the observed race, match or training records and the stated units. Supply independently verified rule editions, calibration tables and targets where requested.

How to use Coggan IF/TSS Normalized Power Calculator and understand its results

Prepare the observed race, match or training records and the stated units. Supply independently verified rule editions, calibration tables and targets where requested.
Enter observedAlreadyRolling30SecondPowerWatts, representedDurationsSeconds, independentlyMeasuredFtpWatts using the field table and calculation rules, then run the tool.
Read normalizedPowerWatts, intensityFactor, modeledTrainingStressScore. The explanation below defines the units, signs, ordering and any flags or placeholder values.
If the tool reports an input issue, correct the values and run it again. Apply the stated assumptions when interpreting a successfully returned result.

Input field	Meaning	Value type; see rules below	Requirement
observedAlreadyRolling30SecondPowerWatts	Observed rolling 30-second power watts	list of number	Required
representedDurationsSeconds	Represented durations seconds	list of number	Required
independentlyMeasuredFtpWatts	Independently measured ftp watts	number	Required

Enter aligned nonempty nonnegative power observations already averaged over 30 seconds, positive durations and positive independently measured FTP. Normalize duration weights and return NP, IF and modeled TSS.

NP=(sum(power^4×duration)/sum(duration))^(1/4); IF=NP/FTP; TSS=hours×IF²×100

Units, indexing, boundary conditions and exceptional cases are defined in the calculation rules above.

Output field	Meaning	Value type
normalizedPowerWatts	Normalized power watts	number
intensityFactor	Intensity factor	number
modeledTrainingStressScore	Modeled training stress score	number

json

{
  "input": {
    "observedAlreadyRolling30SecondPowerWatts": [
      100,
      200
    ],
    "representedDurationsSeconds": [
      30,
      30
    ],
    "independentlyMeasuredFtpWatts": 200
  },
  "output": {
    "normalizedPowerWatts": 170.74764851741443,
    "intensityFactor": 0.8537382425870722,
    "modeledTrainingStressScore": 1.2147816447594377
  }
}

Limitations and assumptions

No raw-series smoothing, readiness, injury prediction or exercise clearance is performed.

Numeric inputs, where present, must be finite. Follow the calculation-specific rules for overflow, underflow and exceptional cases. Numeric lists are limited to 10,000 entries; string lists to 128 strings of at most 128 characters each. The rules above may impose smaller limits. Missing required fields, extra fields, wrong value types and violations of the calculation rules are input errors.

Alternative or Complementary methods

Use FTP Test Calculator: FTP estimates from different test protocols depend on conversion assumptions. Protocol results can differ despite the same athlete. For a complementary task, use Cycling Training Zone Lookup: Cycling power-zone intervals scale from measured FTP. Overlap and absence of matching zones remain visible.

Further background: Normalized Power, Intensity Factor and Training Stress Score.

References

Coggan IF/TSS Normalized Power Calculator — tool.io
Normalized Power, Intensity Factor and Training Stress Score — Andrew Coggan, TrainingPeaks

Similar or alternative tools

FTP Test Calculator
FTP estimates from different test protocols depend on conversion assumptions. Protocol results can differ despite the same athlete.
Cycling Training Zone Lookup
Cycling power-zone intervals scale from measured FTP. Overlap and absence of matching zones remain visible.