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Training Stress Score (TSS) from Power and FTP Calculator

Quantify workout load relative to threshold power.

Calculates TSS = (duration_sec × NP × IF) / (FTP × 3600) × 100, where NP is normalised power, IF = NP/FTP, and FTP is functional threshold power.

Marcus Laurent By Marcus Laurent
Published Last reviewed 1 min read

Inputs

W
W
s

Results

Enter values and click Calculate to see results.
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How to use this calculator

  1. Fill in the inputs above using the units you already have.
  2. Values update automatically as you type — no submit button needed.
  3. Hover any result row for the underlying formula and intermediate values.

Formula

TSS = (s × NP × IF) / (FTP × 3600) × 100

In depth

Calculates TSS = (duration_sec × NP × IF) / (FTP × 3600) × 100, where NP is normalised power, IF = NP/FTP, and FTP is functional threshold power.