Acute:Chronic Workload Ratio Calculator (ACWR)
Acute-to-chronic workload ratio from the last 7 days of training load versus the 28-day average — session RPE × minutes, TSS or distance — with the injury-risk “sweet spot” 0.8–1.3 and next-week load limits.
How it works
ACWR = acute load (7 days) ÷ chronic load (28-day average); EWMA: EWMA_today = λ × load + (1 − λ) × EWMA_yesterday, λ = 2 ÷ (N + 1)
Tim Gabbett’s acute:chronic workload ratio compares what you did this week with what you have been prepared for over the last month. Fitness comes from the chronic load; injury risk comes from the acute load outrunning it. Team-sport data suggest ratios between 0.8 and 1.3 carry the lowest soft-tissue injury risk, while spikes above 1.5 double or quadruple it — and, counter-intuitively, so does under-training, because low chronic load leaves athletes unprepared for the inevitable hard week. Load can be measured with any consistent metric: session-RPE × minutes is universal; TSS, distance or sprint counts work for specific sports. The method has been criticised statistically, so treat it as a planning guardrail rather than a precise predictor.
Worked example
Weeks of 1,700, 1,800, 1,900 and now 2,400 load units: coupled chronic 1,950, ACWR 1.23 — in the sweet spot, though the week jumped 26%. Next week should stay under about 2,535 to remain ≤ 1.3.
Frequently asked questions
Which method is best?
EWMA is more sensitive to recent spikes and predicted injury slightly better in some studies; the coupled average is simplest. Pick one and be consistent.
Does ACWR apply to running?
Yes, with weekly kilometres or run-TSS. Runners often pair it with the 10% weekly increase rule and a down week every third or fourth week.
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General fitness estimate, not medical advice. Calorie and performance figures vary widely between individuals — use them for planning and comparison, and check with a doctor before starting intense training.