TSS calculator

Training Stress Score (TSS) puts one number on how hard a session was. TSS = hours × IF² × 100, where IF (Intensity Factor) is normalized power divided by FTP. One hour flat out at FTP is 100 TSS. Enter a ride, a heart rate session or a run below to get TSS, IF and what it means for recovery.

Calculator

Based on

Duration

Hours:minutes:seconds

Normalized power (NP)

No NP? Average power works for steady rides but underestimates TSS on variable rides.

FTP

TSS

106

Intensity Factor

0.84

Low: Usually recovered by the next day.

Same load as 1:04 at FTP.

TSS = hours × IF² × 100, IF = NP ÷ FTP (Coggan).

What TSS measures

Training Stress Score (TSS) combines how long and how hard a session was into one number. It was developed by Andrew Coggan for power-based cycling training and is now used by almost every training platform, including Intervals.icu and TrainingPeaks. The idea is simple: one hour ridden at exactly your FTP is defined as 100 TSS. Everything else is scaled from there.

That makes very different sessions comparable. A 90-minute sweet spot ride, a 4-hour endurance ride and a 45-minute VO2max session can all be put on the same scale, added up per week and tracked over months. This calculator is part of the free LeCoach cycling calculators.

The TSS formula

For power-based TSS:

TSS = hours × IF² × 100, where IF (Intensity Factor) = normalized power ÷ FTP

Written out in full, this is the same as (seconds × NP × IF) ÷ (FTP × 3,600) × 100.

Normalized power (NP) is a weighted average that accounts for the extra cost of surges. A ride with lots of attacks has a higher NP than its average power. Your bike computer or training platform calculates NP for you.

Worked example. You ride 1 hour 30 minutes with a normalized power of 210 W. Your FTP is 250 W. IF = 210 ÷ 250 = 0.84. TSS = 1.5 × 0.84² × 100 = 106. That is the same training stress as about 1 hour and 4 minutes at FTP.

Because IF is squared, intensity counts much more than duration. Riding 10 % harder for the same time raises TSS by 21 %.

TSS without a power meter

The calculator offers two alternatives:

Heart rate (hrTSS estimate). This uses Banister's TRIMP method, which weights time by how close your heart rate is to its maximum, then scales it so that one hour at your lactate threshold heart rate equals 100. You need your average heart rate, LTHR, resting and maximum heart rate. It works best for steady sessions. For interval sessions it underestimates the load, because heart rate lags behind short efforts.

Run pace (rTSS). For runs, IF is your threshold pace divided by your actual pace (both in seconds per kilometre). One hour at 5:00/km with a threshold pace of 4:30/km gives IF 0.90 and 81 TSS. Use normalized graded pace if your platform gives it; on hilly routes average pace underestimates the effort.

Want this worked out for you every day? LeCoach builds your training around your own numbers.

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What your TSS means

These are the commonly used rule-of-thumb bands for a single session:

TSS	Load	Typical recovery
Under 150	Low	Usually recovered by the next day
150–300	Medium	Some fatigue the next day, gone after 2 days
300–450	High	Residual fatigue for 2 days or more
Over 450	Very high	Several days of fatigue

And typical Intensity Factors:

IF	Session type
Below 0.75	Recovery and endurance rides
0.75–0.85	Tempo, long sweet spot sessions, gran fondos
0.85–0.95	Threshold intervals, road races
0.95–1.05	Time trials of around an hour, hard criteriums
Above 1.05	Short time trials, prologues, very hard short sessions

From TSS to fitness, fatigue and form

TSS is most useful added up over time. Three numbers are derived from your daily TSS:

Fitness (CTL): the rolling average of daily TSS over about 42 days. It rises slowly as you build training.
Fatigue (ATL): the same over about 7 days. It reacts quickly to hard weeks.
Form (TSB): fitness minus fatigue. Negative while you are building, positive when you are fresh.

A typical sustainable increase is a few CTL points per week. Big jumps raise the risk of overreaching. Our weekly training volume planner shows how to build load step by step, and the article TSS explained for cyclists goes deeper into the numbers.

Common mistakes

Using an outdated FTP. If your FTP is set too low, every session scores too high, and the other way round. Recalculate it with the FTP calculator.
Using average power instead of NP for variable rides. Average power underestimates TSS on group rides and races.
Treating 100 TSS of endurance and 100 TSS of intervals as equal. They are equal in total stress, not in the kind of fatigue or the adaptation they cause. TSS says how much, not what.
Comparing TSS across sports without care. A 100 TSS run usually costs more recovery than a 100 TSS ride because of the impact.
Chasing a weekly TSS target. TSS is a measure, not a goal. Hitting a number with junk miles is worse than missing it with good sessions.

When TSS gets it wrong

Very long rides at low intensity can score lower than they feel, because TSS does not capture fuelling, muscle damage or the strain of five or six hours on the bike.
Heat and altitude raise the real cost of a session without changing power-based TSS.
Short maximal efforts, like sprints, score low but are very taxing on the nervous system.
Heart rate TSS reads low on interval sessions and high on hot days.

LeCoach tracks your fitness, fatigue and form from every session you sync through Intervals.icu. Its Plan Health check flags it when your planned and actual load drift apart, so you can adjust the plan before fatigue builds up.

Sources

Allen H, Coggan A, McGregor S. Training and Racing with a Power Meter, 3rd edition. VeloPress, 2019.
Banister EW. Modeling elite athletic performance. In: Physiological Testing of Elite Athletes. Human Kinetics, 1991.
Coggan AR. Training Stress Score and Intensity Factor. TrainingPeaks.

Frequently asked questions

How do you calculate TSS?

TSS = hours × IF² × 100, where IF is normalized power divided by FTP. A 90-minute ride at a normalized power of 210 W with a 250 W FTP has IF 0.84 and scores 1.5 × 0.84² × 100 = 106 TSS.

What is a good TSS for a ride?

It depends on your goals and fitness. An endurance ride of 2 hours typically scores about 90 to 130. A hard interval session of 60 to 90 minutes often scores 70 to 120. A long gran fondo can reach 250 to 400. Under 150 is usually recovered by the next day.

How much TSS per week should I do?

It depends on your fitness and available time. Recreational riders often sit around 250 to 400 TSS per week, committed amateurs 400 to 700, and riders with a lot of time more than that. Increase gradually, by roughly 5 to 10 % per week, and plan recovery weeks.

What is Intensity Factor?

Intensity Factor is normalized power divided by FTP. It describes how hard a session was relative to your threshold. An IF of 1.00 means you rode at FTP; recovery rides are usually below 0.65, endurance rides 0.65 to 0.75 and threshold sessions 0.85 to 0.95.

Can I calculate TSS from heart rate?

Yes, as an estimate. The heart rate method in the calculator uses Banister's TRIMP, scaled so one hour at your threshold heart rate equals 100. It is reasonable for steady rides and underestimates interval sessions, because heart rate lags behind short efforts.

Is 100 TSS a hard workout?

100 TSS equals one hour at FTP, which is hard. But a 2-hour endurance ride also scores about 100. Whether it feels hard depends on intensity, not only on the number. Look at IF alongside TSS.

What is the difference between TSS and training load in Garmin or Strava?

Each platform uses its own model. Garmin's training load is based on EPOC, and Strava's relative effort on heart rate. TSS is based on power relative to FTP, which makes it the most precise for cyclists with a power meter. Do not mix scales when comparing weeks.