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TSS Calculator

Updated Sep 2026 Used 0 times
Enter the measured valuesUse values from one internally consistent test or planning scenario.
Elapsed workout duration used by the score.
Use the platform-calculated NP value.
Used for Variability Index and work cross-check.
Use the FTP that applied on the workout date.

Guest calculations stay on this device. Signed-in results sync privately.

Your result

Power-based training stress

Enter your values, then calculate to see a verified result.

Inputs usedReview the information used for this result.
Full calculation and sourcesOpen Full calculation and sources to audit the formula, assumptions, fixtures, and interpretation limits.

Versioned calculationFormula v1.0.0

Method reviewed 2026-09-27TrainingPeaks - glossary of FTP, IF, NP and TSS metrics; TrainingPeaks - Training Stress Score formulaFormula v1.0.0

Method shown

The selected equation and assumptions stay visible.

Cross-checked

Supporting outputs expose unit and protocol mistakes.

Actionable

The result links to the next relevant planning task.

Result actions
1
Step 1Enter workout duration.90-minute power workout
2
Step 2Enter normalized and average power from the same file.90-minute power workout
3
Step 3Enter the FTP active for that session.90-minute power workout

Interpretation

The metric depends on current FTP and accurate power-meter data.

Running, swimming, and heart-rate stress scores use different implementations.

A score does not determine readiness, injury risk, or required recovery by itself.

Use this result

Keep exploring

4 available tools
FTP CalculatorEstimate cycling FTP from a selected field-test protocol.Training Zones GeneratorBuild a transparent 3-, 5-, or 6-zone table.Weekly Volume CalculatorCompare a target week with recent training volume.Brick Workout CalculatorPlan a bike-to-run session and transition.
Public verification recordFormula v1.0.0
Review scope
IF, Squared Intensity, Duration Conversion, VI, Work, And Average-power Consistency.
Review team
CalculatorGeek Expert Review Team
Verified
2026-09-27
Next source review
2027-03-27
Automated fixtures
1 cases

Review method

Recompute IF = NP / FTP; TSS = duration hours x IF squared x 100; VI = NP / average power. independently; verify unit normalization, protocol selection, internal consistency, and invalid boundaries.

Known limitations

  • The metric depends on current FTP and accurate power-meter data.
  • Running, swimming, and heart-rate stress scores use different implementations.
  • A score does not determine readiness, injury risk, or required recovery by itself.

Primary sources

Latest update

2026-09-27 ยท Added complete endurance-suite calculator with verified model, source ledger, premium result, and unified contextual navigation.

Published calculation checks

CaseInputsExpected result
90-minute power workoutduration_minutes=90 min, normalized_power_watts=210 w, average_power_watts=200 w, ftp_watts=250 wintensity_factor=0.84, training_stress_score=105.84, variability_index=1.05
On this page

Direct answer

Power-based TSS equals workout hours multiplied by Intensity Factor squared and 100, where IF is normalized power divided by FTP.

One hour at FTP produces 100 points by definition. The result depends on valid power data and a current FTP.

Calculate the anchor with the FTP Calculator and compare weekly distance separately with the Weekly Volume Calculator.

How to use the calculator

  1. Enter workout duration.
  2. Enter normalized and average power from the same file.
  3. Enter the FTP active for that session.
  4. Compare trends without treating the number as a recovery diagnosis.

Continue with Check the worked example or Interpret the result safely for the next calculation.

Inputs, outputs, and result meaning

Inputs

  • Workout duration: Elapsed workout duration used by the score.
  • Normalized Power: Use the platform-calculated NP value.
  • Average power: Used for Variability Index and work cross-check.
  • Functional threshold power: Use the FTP that applied on the workout date.

Outputs

  • Training Stress Score: A displayed result from the stated method and the entered assumptions.
  • Intensity Factor: A displayed result from the stated method and the entered assumptions.
  • Variability Index: A displayed result from the stated method and the entered assumptions.
  • Mechanical work: A displayed result from the stated method and the entered assumptions.
  • Equivalent FTP minutes: A displayed result from the stated method and the entered assumptions.

Formula and methodology

Method: IF = NP / FTP; TSS = duration hours x IF squared x 100; VI = NP / average power.

The equation is the published TrainingPeaks power-based score. TSS, NP, and IF are registered metrics of Peaksware, LLC.

Worked examples

90 minutes at NP 210 W and FTP 250 W

IF is 0.84. TSS is 1.5 x 0.84 squared x 100 = 105.84.

Interpretation and limitations

  • The metric depends on current FTP and accurate power-meter data.
  • Running, swimming, and heart-rate stress scores use different implementations.
  • A score does not determine readiness, injury risk, or required recovery by itself.

Frequently asked questions

Why is one hour at FTP equal to 100?

That is how the metric is defined.

Can average power replace NP?

Only as a rough steady-session approximation; variable workouts can differ materially.

Why can two platforms disagree?

FTP settings, file processing, pauses, and NP implementation can differ.

How should I compare results over time?

Repeat the same protocol, units, equipment setup, and environmental conditions, then review the supporting outputs rather than only the headline number.

Sources and transparency

CalculatorGeek independently recomputed every published fixture on 2026-09-27. Sources establish the equation, protocol, or interpretation boundary; they do not turn an estimate into a laboratory measurement or personalized advice.