Running calculator
Weekly mileage ramp calculator
Check this week against the last four with the acute:chronic workload ratio, and get the safe ceiling for next week from both the 10% rule and ACWR. Free, instant, no sign-up.
Use the same unit for every week — kilometres or miles, it only compares like with like.
Ramping safely is mostly about what you do on the easy days — the coach builds the week, not just the total.
What the acute:chronic ratio measures
Acute load is what you did this week. Chronic load is the average of the last four — roughly, what your body is used to. The ratio between them says whether this week is a normal day at the office or a shock. Injury risk tracks that ratio far better than it tracks raw mileage: 60 km is routine for someone averaging 60 and reckless for someone averaging 25.
The zones
Below 0.8 you are detraining relative to what you have already absorbed. Between 0.8 and 1.3 is the sweet spot, where the work is enough to adapt to and not enough to break you. Past 1.3 risk climbs, and past 1.5 it climbs steeply. These are population bands rather than personal thresholds, so treat them as a speed limit and not a guarantee.
Why two ceilings, not one
The 10% rule only looks at last week, so after a layoff it happily green-lights a jump that lands you deep in the danger band. ACWR only looks at the four-week average, so during a taper it permits a week far above last week's. They disagree exactly where it matters, and this calculator shows both and caps at the lower of the two — a single number would have to choose which failure to hide.
What this does not know
Distance is a crude proxy for load. It cannot see intensity, terrain, surface, sleep, life stress or whether you are coming back from injury — all of which move risk as much as volume does. A week of hill repeats and an easy week of the same distance are not the same week. Use the ceiling as an upper bound, not as a target to hit.