Training Stress Score (TSS) Calculator
Training Stress Score (TSS), developed by Andrew Coggan, is the standard metric for quantifying cycling training load in a way that accounts for both duration and intensity. A TSS of 100 represents a 1-hour maximal effort at exactly FTP. TSS allows you to compare a hard 90-minute ride with an easy 3-hour ride and track cumulative fatigue using models such as Chronic Training Load (CTL), Acute Training Load (ATL), and Training Stress Balance (TSB). Enter your ride duration, normalized power (from your cycling computer), and FTP to calculate TSS.
TSS formula
IF = NP / FTP
TSS = (duration(s) × NP × IF) / (FTP × 3,600) × 100
For a 90-minute (5,400 second) ride at NP = 250 watts with FTP = 280: IF = 250/280 = 0.893. TSS = (5,400 x 250 x 0.893) / (280 x 3,600) x 100 = (1,205,550) / (1,008,000) x 100 = 119.60. This indicates a moderately high training stress with significant next-day fatigue expected.
TSS interpretation guide
- Under 150: Low. Minimal residual fatigue, fully recovered next day.
- 150 to 300: Moderate. Some fatigue, recover within 24 hours.
- 300 to 450: High. Significant fatigue, 1 to 2 days needed for recovery.
- Above 450: Very high. Seen in long races or stage racing days. Expect 2 to 3 days recovery.
TSS calculator: frequently asked questions
What is Training Stress Score (TSS)?
TSS is a metric developed by Andrew Coggan that quantifies the training load of a cycling workout. A score of 100 represents an effort equivalent to a 1-hour all-out ride at FTP. TSS values allow you to compare workouts of different durations and intensities and track cumulative fatigue over time.
What is the TSS formula?
TSS = (duration in seconds x normalized power x intensity factor) / (FTP x 3,600) x 100. Intensity factor (IF) = normalized power / FTP. Normalized power (NP) is a power-weighted average that accounts for variability in power output and is typically calculated by cycling software from power meter data.
What does a TSS value mean in practice?
As a rough guide: below 150 TSS is low stress with little residual fatigue, 150 to 300 is moderate (some next-day fatigue), 300 to 450 is high (significant fatigue, needs 1 to 2 days recovery), and above 450 is very high (seen in hard stage race days). A typical training week for an amateur cyclist might total 400 to 700 TSS.
What is intensity factor (IF)?
IF is the ratio of normalized power to FTP. An IF of 1.0 means you averaged exactly FTP power for the ride. IF below 0.75 is an easy endurance ride. IF of 0.75 to 0.85 is tempo/moderate. IF of 0.85 to 0.95 is threshold work. IF above 0.95 is at or above FTP, typically only sustainable for shorter durations.
Can I calculate TSS without a power meter?
Without a power meter, heart rate-based TSS (hrTSS) can be estimated using heart rate data and lactate threshold heart rate. The formula is similar but uses heart rate intensity factor instead of power IF. Most training platforms (TrainingPeaks, Garmin Connect) can calculate hrTSS from heart rate monitor data.
Official sources
- Allen, H., & Coggan, A.R. (2010). Training and Racing with a Power Meter. VeloPress. (TSS formula and interpretation).
- American College of Sports Medicine: acsm.org.
- Union Cycliste Internationale: uci.org.
Reviewed by the CalculatorHub team, edited by James Graham, 15 June 2026. See our methodology.