TSS Calculator

What is Training Stress Score (TSS)?

Training Stress Score (TSS) quantifies the physiological cost of a workout on a single scale. Developed by Dr. Andrew Coggan, it combines workout duration, intensity, and your personal fitness level (FTP) into one number.

A TSS of 100 equals the stress of riding at your FTP for exactly one hour. An easy 2-hour ride might score 80 TSS, while a hard 1-hour criterium could score 120+.

The TSS Formula

TSS is calculated as:

TSS = (duration in seconds x NP x IF) / (FTP x 3600) x 100

Where:

• NP = Normalized Power — a weighted average that accounts for the variability of your effort
• IF = Intensity Factor = NP / FTP — how hard the ride was relative to your threshold
• FTP = Functional Threshold Power — your personal baseline

How to Use TSS

• <150 TSS: Low stress, recoverable within 24 hours
• 150–300 TSS: Medium stress, some residual fatigue next day
• 300–450 TSS: High stress, likely need 2+ days recovery
• >450 TSS: Very high, extended recovery required

Daily TSS feeds into your Chronic Training Load (CTL = fitness), Acute Training Load (ATL = fatigue), and Training Stress Balance (TSB = form). These three metrics form the Performance Management Chart — the most powerful tool for managing training load over time.