Acute:chronic workload ratio calculator
Your ACWR compares the training you have done in the last 7 days with your weekly average over the last 28 days. Enter your last four weekly totals below and the calculator returns your ratio: 0.8 to 1.3 is the range most coaches treat as sustainable, above 1.5 is a spike, and below 0.8 means you are detraining.
Your weekly training load — last four weeks
Use minutes, kilometres or RPE × minutes — the same unit for all four weeks.
7-day load
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Weekly average
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Week on week
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Your acute:chronic ratio
Fill in at least this week and one earlier week
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ACWR = this week’s load ÷ your average week across the weeks entered (up to four). An estimate to prompt a decision, not a diagnosis.
What the acute:chronic workload ratio actually measures
The ratio answers one question: is this week's training bigger than what my body is used to? The "acute" side is your recent load — normally the last 7 days. The "chronic" side is your four-week base, averaged into a single week. Divide one by the other and you get a number that is comparable across runners who train very different volumes.
This is why the ratio is more useful than mileage alone. A runner going from 30 km to 45 km a week has made the same relative jump as a runner going from 60 km to 90 km, even though the absolute difference is 15 km versus 30 km. Both have increased load by 50 per cent, and both carry a similar risk of doing too much too soon.
The formula
ACWR = acute load (last 7 days) ÷ (chronic load (last 28 days) ÷ 4)
Worked example: you ran 300 minutes in the last 7 days and 1,000 minutes across the last 28. Your chronic weekly average is 1,000 ÷ 4 = 250 minutes. Your ratio is 300 ÷ 250 = 1.20, which sits comfortably in the sustainable range.
Now imagine a good week: 400 minutes in the last 7 days against the same 1,000-minute base. That is 400 ÷ 250 = 1.60. Nothing about that week was wrong in isolation, but it was a 60 per cent jump on what the previous month had prepared you for.
How to read each band
| Ratio | What it means | What to do |
|---|---|---|
| Below 0.8 | Acute load well under your norm | Good after a break or illness — rebuild gradually rather than returning to old volume in one week |
| 0.8 – 1.3 | Building at a sustainable rate | Carry on. Progress by roughly 5–10 per cent per week |
| 1.3 – 1.5 | Sharp build | Acceptable for a short block if sleep and recovery are good |
| Above 1.5 | Spike | Hold volume steady for two weeks; keep intensity but cut the extra mileage |
Three things that catch people out
1. Intensity hides inside minutes
Two 60-minute runs are not the same load if one was easy and the other was a hard threshold session. If you want the ratio to reflect effort, use RPE × minutes: an easy 60-minute run at RPE 4 scores 240, a hard 60-minute session at RPE 8 scores 480.
2. Cross-training counts, but only for the sport you are loading
A big cycling week raises your general load without preparing your legs for running impact. For runners, the most useful ratio is usually calculated on running alone, with cycling and gym work tracked separately.
3. The ratio lags reality
Because the chronic side is a 28-day average, it moves slowly. After a two-week holiday your ratio will read high on the first week back even if that week felt easy. In that situation, treat the number as a warning to extend the rebuild, not as a reason to stay off your feet.
How to log your load in twenty seconds
The ratio is only as good as the numbers you feed it, and the usual reason people abandon ACWR is that collecting the data feels like admin. Keep it cheap: at the end of each week, add up the minutes you trained and write that single number down. Minutes are enough. If you want intensity reflected, use RPE × minutes — a 60-minute easy run at effort 4 scores 240, a 60-minute threshold session at effort 8 scores 480.
Two habits make the number trustworthy. First, use the same unit every week; mixing kilometres one month and minutes the next renders every comparison meaningless. Second, count gym work and cross-training if you do them — load is time under stress, and pretending a heavy leg day did not happen is how a ratio ends up reassuring while your calves disagree. Whatever your platform calls the field, "relative effort", "training load" or a manual note all work, as long as the tally is consistent.
Where the ratio gets criticised
ACWR has been adopted widely and questioned seriously. The main objection is statistical: it divides one rolling average by another built from overlapping weeks, which can produce dramatic-looking ratios from ordinary training. A quiet patch in the chronic window lowers the denominator and inflates the ratio without any genuine spike, while a returning runner with one big week can look far riskier than they are.
Follow-up work has also struggled to reproduce the original injury-prediction results, and the strength of the association shrinks once you account for how much training someone has done overall. None of that makes the idea useless — the pattern of sudden jumps followed by trouble is real and familiar to every coach. It does mean the ratio should be read as a prompt to look at the calendar, not as a verdict. Pair it with sleep, soreness, how sessions feel, and whether your easy days are genuinely easy.
Pairing load with the rest of your data
A ratio on its own tells you whether load is changing, not whether you are getting fitter. Read it alongside two other numbers: your race time predictions, which show whether the training is converting into speed, and your easy-to-hard split, which shows whether the load is being built in the right proportions. A rising ratio with improving predictions is a training block working. A rising ratio with flat predictions usually means volume without purpose.
How CollinghamCo Active calculates it for you
Members do not have to add up four weeks of training by hand. The dashboard derives acute and chronic load from synced Strava sessions, plots the ratio over time, and flags weeks where the jump crosses into spike territory — alongside weather-adjusted pace and club comparisons so you can see whether a hard week was actually hard or just windy.
Frequently asked questions
What is a good acute:chronic workload ratio?+
Most sports-science guidance points to 0.8–1.3 as the range where training load is building without a sudden jump. Below 0.8 suggests you are detraining; above 1.5 is usually treated as a spike worth addressing.
Should I measure load in minutes, kilometres or RPE?+
Any of them works as long as you use the same unit for both numbers. Minutes are the simplest. For a more accurate picture of intensity, multiply session duration in minutes by perceived effort out of ten (RPE × minutes).
Why is the chronic window 28 days?+
Four weeks is long enough to capture a full training block and short enough that it still reflects your current fitness. It also matches the rolling windows used in most training-load research.
Does a high ratio mean I will get injured?+
No. It is a risk indicator, not a diagnosis. Ratios above 1.5 are more common in athletes who then report niggles, but sleep, stress, strength work and running history matter at least as much.
Does weight training or cycling count towards load?+
It should. Load is about time under stress, so add gym sessions and cross-training in the same units. If you separate them, calculate a ratio per sport — a big cycling week does not protect you from a running spike.
How often should I check my ratio?+
Weekly is enough for most club runners. Check it on the same day each week, ideally before your hardest session, and look at the trend across four to six weeks rather than any single number.
Why does the calculator ask for four weekly totals instead of 28 days?+
Four weekly totals give the same answer with far less adding up: the 28-day total divided by four is simply the average of those four weeks. Entering weeks also shows the ramp you actually took, which matters as much as the final ratio — a jump that happened two weeks ago is a different situation from one that happened this week.
Is the acute:chronic workload ratio controversial?+
Yes, and it is worth knowing why. The ratio divides two rolling averages built from overlapping data, which can create statistical artefacts: the same training pattern can produce a high ratio with no real spike, and small changes in a quiet week move the number sharply. Most researchers now treat ACWR as a conversation starter that flags weeks worth reviewing, not a predictive test. Use it alongside sleep, soreness, how sessions feel and your own history.
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