What is Normalized Power and how does it differ from average power?

Normalized Power is a weighted-average metric that accounts for the non-linear physiological cost of variable efforts. A ride with many surges above threshold can have the same average power as a steady ride, but NP will be higher for the variable session because short high-intensity intervals incur disproportionate metabolic cost. NP is computed using a 30-second rolling average raised to the fourth power, then the fourth root of the mean.

What TSS values correspond to different workout types?

A one-hour ride at FTP yields a TSS of 100 by definition. Easy recovery spins typically range from 20–40 TSS, tempo sessions from 50–80, and threshold intervals from 80–120. Long endurance rides can accumulate 150–300+ TSS depending on duration and terrain. These ranges are descriptive, not prescriptive; individual tolerance varies with training history and weekly load.

How often does FTP need to be retested for accurate TSS?

FTP can change measurably within 4–8 weeks during focused training blocks or after periods of detraining. Many structured programs include FTP assessments every 6–8 weeks. Using an outdated FTP value will skew Intensity Factor and therefore TSS; if FTP has increased but the entered value remains stale, recent workouts will appear artificially hard and TSS will be inflated.

Can TSS be used for activities other than cycling?

The original TSS formula is specific to power-meter cycling data. Running TSS (rTSS) adaptations use pace and Grade Adjusted Pace instead of power; swimming TSS (sTSS) relies on pace zones and perceived effort. These variants adjust the underlying math to fit the physiological demands of each sport. This calculator implements only the cycling power-based version.

What is the relationship between TSS and recovery time?

Empirical guidelines from TrainingPeaks suggest that workouts under 150 TSS may require less than 24 hours of recovery, sessions from 150–300 TSS may need 1–2 days, and efforts above 300 TSS can necessitate 2+ days before high-intensity work resumes. These are population averages; actual recovery depends on training status, nutrition, sleep quality, and accumulated fatigue from prior days.

Cycling

Training Stress Score (TSS) Calculator

Calculate Training Stress Score from workout duration, Normalized Power, and FTP.

Last updated: 22 April 2026

What this tool does

This calculator computes Training Stress Score (TSS) using the method developed by Dr. Andrew Coggan, quantifying the physiological strain of a cycling workout. It requires workout duration in hours, Normalized Power in watts, and Functional Threshold Power (FTP) in watts, then outputs a TSS value where 100 points represents one hour at threshold intensity. The score accounts for both workout duration and intensity through the Intensity Factor (Normalized Power divided by FTP), providing a standardized metric for comparing training loads across different sessions.

Inputs

Result

—

Formula Used

TSS = \frac{t _{h o u r s} \times NP \times IF}{FTP} \times 100, IF = \frac{NP}{FTP}

t

Duration in hours

NP

Normalised power in watts

FTP

Functional threshold power in watts

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How Training Stress Score (TSS) Calculator works

This calculator implements the Andrew Coggan TSS formula to quantify the training load of a single cycling workout. It multiplies workout duration, Normalized Power (NP), and Intensity Factor (IF) to produce a dimensionless score that accounts for both the intensity and volume of the session. TSS is widely used in structured training programs to track cumulative fatigue and guide recovery timing.

The formula

The canonical formula is:

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

where IF (Intensity Factor) = NP / FTP. Because duration is collected in hours and the 3600-second constants cancel, the implemented calculation simplifies to:

TSS = (duration_hours × NP × IF / FTP) × 100

Normalized Power represents an estimate of the physiological cost of variable-power efforts, and Functional Threshold Power (FTP) is the highest mean power sustainable for approximately one hour.

Where this method is most accurate

TSS assumes FTP is current and accurately measured—typically via a 20-minute or ramp test with validated protocols. Normalized Power algorithms rely on power-meter data sampled at 1-second intervals; indoor-trainer or head-unit-computed NP values may differ slightly from post-ride analysis software. The model is calibrated for steady-state and interval workouts in the 30-minute to 3-hour range; very short sprints and ultra-endurance rides above 6 hours may fall outside the IF-to-physiological-cost relationship originally validated.

What this tool does not do

This calculator does not measure fitness, prescribe training zones, or recommend workout frequency. It does not account for non-cycling stressors (strength training, sleep debt, nutrition status) that affect recovery capacity. TSS is an estimate of relative load; identical scores from different riders do not imply equivalent fatigue. The tool does not validate whether entered NP and FTP values are physiologically plausible or suggest adjustments to training plans.

Disclaimer

This calculator is an educational tool for exploring the Training Stress Score concept as published by Andrew Coggan. It is not medical, coaching, or performance advice. Entries and outputs are estimates based on user-supplied data. Consult a certified coach or sports-medicine professional before modifying training volume or intensity.

Questions

What is Normalized Power and how does it differ from average power?: Normalized Power is a weighted-average metric that accounts for the non-linear physiological cost of variable efforts. A ride with many surges above threshold can have the same average power as a steady ride, but NP will be higher for the variable session because short high-intensity intervals incur disproportionate metabolic cost. NP is computed using a 30-second rolling average raised to the fourth power, then the fourth root of the mean.
What TSS values correspond to different workout types?: A one-hour ride at FTP yields a TSS of 100 by definition. Easy recovery spins typically range from 20–40 TSS, tempo sessions from 50–80, and threshold intervals from 80–120. Long endurance rides can accumulate 150–300+ TSS depending on duration and terrain. These ranges are descriptive, not prescriptive; individual tolerance varies with training history and weekly load.
How often does FTP need to be retested for accurate TSS?: FTP can change measurably within 4–8 weeks during focused training blocks or after periods of detraining. Many structured programs include FTP assessments every 6–8 weeks. Using an outdated FTP value will skew Intensity Factor and therefore TSS; if FTP has increased but the entered value remains stale, recent workouts will appear artificially hard and TSS will be inflated.
Can TSS be used for activities other than cycling?: The original TSS formula is specific to power-meter cycling data. Running TSS (rTSS) adaptations use pace and Grade Adjusted Pace instead of power; swimming TSS (sTSS) relies on pace zones and perceived effort. These variants adjust the underlying math to fit the physiological demands of each sport. This calculator implements only the cycling power-based version.
What is the relationship between TSS and recovery time?: Empirical guidelines from TrainingPeaks suggest that workouts under 150 TSS may require less than 24 hours of recovery, sessions from 150–300 TSS may need 1–2 days, and efforts above 300 TSS can necessitate 2+ days before high-intensity work resumes. These are population averages; actual recovery depends on training status, nutrition, sleep quality, and accumulated fatigue from prior days.

Sources & Methodology

Implements TSS = (duration_hours × 3600 × NP × IF) / (FTP × 3600) × 100, where IF = NP / FTP. The formula originates from Andrew Coggan's work with TrainingPeaks and is documented in *Training and Racing with a Power Meter*. Duration converts from hours to seconds, then the 3600-second constants cancel.

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