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TRAINING LOAD CALCULATOR

Enter your starting CTL and ATL, then your daily TSS. See how recorded training and rest days change the three numbers.

STARTING LOAD

Use your CTL and ATL from the end of the day before Day 1. If you leave both at zero, the result is a model starting from no prior load, not an estimate of your current fitness.

Example buttons repeat a seven-day pattern across the entered days. These are demonstration values, not recommended training weeks. Enter every calendar day in order, including zero for rest days.

D1
D2
D3
D4
D5
D6
D7

METHODOLOGY

The calculator follows the daily recurrences in TrainingPeaks’ help documentation, with time constants of 42 days for CTL and 7 for ATL. Starting CTL and ATL apply to the day before your first entry. Every entry advances the model by one day.

CTL today = CTL yesterday + (TSS today − CTL yesterday) / 42. Read the TrainingPeaks CTL definition and formula.

ATL today = ATL yesterday + (TSS today − ATL yesterday) / 7. The shorter time constant makes ATL respond more quickly to the entered load. See the TrainingPeaks ATL definition and formula.

TSB today = CTL yesterday − ATL yesterday. TrainingPeaks uses the preceding day’s values; subtracting today’s end-of-day values gives the following day’s TSB. See the TrainingPeaks TSB documentation.

Worked example: start with CTL 60 and ATL 90, then enter one rest day at 0 TSS. That day’s TSB is −30. By the end of the day, CTL is 58.6 and ATL is 77.1; the following day’s TSB is −18.6. Those are changes in the model, not measured changes in your body.

Comparing platforms: differences in starting values, missing days, TSS inputs, time constants and the day assigned to TSB can change the result. This tool uses the fixed defaults above and rounds only for display.

TrainingPeaks uses the labels Fitness, Fatigue and Form for CTL, ATL and TSB. The calculation uses training scores; it does not directly measure those physical states. Two diaries with identical daily TSS and starting values produce identical outputs here, even if the rides and the riders’ responses differ.

Method checked 7 September 2026 · Tool version 2.0

FROM HERE

ARTICLEManaging Training Load in Your 40s and 50sAfter 40, the limiter usually isn't the training — it's how much load you can absorb. Managing that load deliberately, with simple monitoring, is what separates riders who keep improving from riders who keep breaking down. Here's how to track it and act on it.PODCASTStrength Training For Cycling Simplified | Derek Teelwith Derek TeelARTICLEHow to Read Your Training Data: TSS, CTL, ATL, and TSB Without the JargonMost amateur cyclists have a TrainingPeaks account they barely read. The numbers there — TSS, CTL, ATL, TSB — are not as complicated as they look. Here's the field guide for reading them properly, and the three signals worth acting on.ARTICLEHow to Use Training Load Without Overthinking ItThe Performance Management Chart is a tool, not a coach. Here is how to use training load numbers without letting them use you.

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