Fitness, Fatigue & Form Calculator (CTL / ATL / TSB)
Enter the weekly TSS you've logged for the last twelve weeks and watch your fitness (CTL), fatigue (ATL), and form (TSB) build into a Performance Management Chart — the same readiness picture PaceBeats plots on your dashboard, so you can see exactly when your form peaks.
Weekly TSS · last 12 weeks
Current form (TSB)
-4
CTL − ATL
Fitness (CTL)
51
42-day load
Fatigue (ATL)
56
7-day load
How to use it
- 1Enter your weekly TSS for each of the last twelve weeks — the list seeds with a realistic ramping build you can replace.
- 2Edit any week to match your own log; the chart and numbers recompute the moment you type.
- 3Read your current Form (TSB) and the label that tells you whether you're fresh, productive, or overloaded.
- 4Watch the fitness (CTL) and fatigue (ATL) lines to see how a hard week spikes fatigue while fitness climbs slowly.
- 5Hit Reset to sample build to drop back to the demo ramp and experiment from a clean slate.
Fitness, fatigue, and form in one chart
CTL is your Chronic Training Load — a 42-day moving average of daily TSS that tracks the fitness you've banked. ATL is your Acute Training Load — a 7-day average that tracks the fatigue you're carrying right now. TSB, your Training Stress Balance, is just CTL minus ATL: the gap between fitness and fatigue, which is your form. Plotted together across a block, those three lines are the Performance Management Chart that tells you whether you're building, holding, or digging a hole.
Form is what you taper for
A positive TSB means your fast-decaying fatigue has dropped below your slow-decaying fitness — fresh legs sitting on top of a season of work, the state you want on race morning. A deeply negative TSB means fatigue has outrun fitness: productive inside a build, but a red flag if it stays there for weeks. This chart makes the trade visible, so you can push CTL during a build and then let ATL fall away into the taper instead of guessing when you're ready.
Built from the TSS you already score
Every CTL and ATL point is driven by daily TSS — the same Training Stress Score the TSS calculator computes for a single bike, run, swim, or strength session. Score your weeks there, drop the weekly totals in here, and you get the readiness curve PaceBeats keeps live from your synced activities and rolls forward when its taper solver projects your race-day form.
How the math works
CTL and ATL are exponentially weighted moving averages of your daily TSS: each day's value = yesterday's + (today's TSS − yesterday's) × (1 − e^(−1/τ)), with τ = 42 days for CTL (fitness) and τ = 7 days for ATL (fatigue). TSB (form) is simply CTL − ATL. This calculator spreads each week's TSS evenly across seven days, fills rest gaps with zero-TSS days so a sparse log can't inflate fitness, and rolls the EWMA forward day by day — the identical Performance Management Chart math the PaceBeats dashboard plots from your synced activities and the taper solver projects toward race day.
Built and reviewed by the PaceBeats coaching-engine team. Every calculator runs the same sports-science math that powers the app's adaptive plans.
Common questions
What CTL should I aim for?
CTL tracks the weekly TSS you sustain, so the right number scales with your race. Age-groupers build to roughly 70–90 CTL for a 70.3 and 90–130 for an Ironman; sprint and Olympic racers peak lower. Chase a steady ramp of about 3–7 CTL per week rather than a fixed ceiling — the jump from where you are matters more than the absolute number, and ramping faster than that is where injury and burnout start.
What TSB (form) is best on race day?
Line up race day with a TSB between +5 and +25. That window means your 42-day fitness is intact while your 7-day fatigue has dropped — fresh legs without detraining. Below 0 you carry too much fatigue to race your fitness; above +25 you've shed enough load that sharpness and CTL start to slip. A two-to-three-week taper that trims volume while holding intensity moves form into that band, which is exactly what the taper calculator projects.
Next step
Turn these numbers into an adaptive plan.
PaceBeats uses this exact math — and your training history — to build and adapt your swim, bike, run, and strength week after week.