Training Stress Balance Calculator (CTL, ATL & TSB)
Project fitness (CTL), fatigue (ATL) and form (TSB) from your current values and a planned daily TSS — plan a taper or a build with the performance management chart method.
How it works
Each day: CTL = CTL + (TSS − CTL) ÷ 42 · ATL = ATL + (TSS − ATL) ÷ 7 · TSB = CTL − ATL
The performance management model (Coggan, based on Banister's fitness–fatigue model) tracks two exponentially weighted averages of daily Training Stress Score: chronic training load (CTL, 42-day time constant) as “fitness” and acute training load (ATL, 7-day) as “fatigue”. Their difference, training stress balance (TSB), is “form”: strongly negative during hard building blocks and positive after a taper. TrainingPeaks describes TSB of +5 to +25 as fresh and race-ready, −10 to −30 as an optimal training range and below −30 as high risk.
Worked example
Starting from CTL 50 and ATL 60, a 14-day taper averaging 40 TSS per day ends with CTL 47.1 and ATL 42.3, so TSB = 47.1 − 42.3 = 4.8 — the top of the neutral zone, just short of Fresh (+5), at the cost of 2.9 points of fitness.
Sources: TrainingPeaks — A coach's guide to ATL, CTL and TSB · Allen H, Coggan A, McGregor S (2019) Training and Racing with a Power Meter, 3rd ed. VeloPress
Frequently asked questions
What TSB should I race at?
Most athletes perform best with TSB between about +5 and +25 on race day — positive enough to be fresh, but without a long taper that loses fitness. Shorter races tolerate a slightly lower TSB than long ones.
Where do I find my CTL and ATL?
Training apps such as TrainingPeaks, Intervals.icu or Golden Cheetah show them on the fitness/performance chart. If you only know weekly TSS, a rough steady-state CTL equals your average daily TSS over the past 6 weeks.
How fast should CTL rise?
A ramp rate of about 3–7 CTL points per week is a common guideline for a build; higher ramps raise the risk of illness, injury and overreaching.
Why does my app show slightly different numbers?
Some apps use a true exponential decay (1 − e^(−1/42)) rather than the simple 1/42 factor, and many calculate TSB from the previous day's CTL and ATL. Differences are usually under one point.
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This calculator gives an estimate for general fitness and education only. It is not a diagnosis — field tests and prediction equations can differ from laboratory measurements, so talk to a doctor or qualified exercise professional before acting on the result, especially before maximal testing.