📈 Weekly Mileage Progression Calculator (10% Rule)

Enter your current weekly running mileage and a target to see a safe progressive increase using the commonly cited 10% rule — capping weekly mileage increases to reduce injury risk.

Current Weekly Mileage

Target Weekly Mileage

Compounding at ten percent

Each week is the previous week multiplied by 1.10, and the last week is trimmed so you land exactly on the target rather than overshooting it:

week n = week (n-1) × 1.10
weeks  = ceil( ln(target / current) / ln(1.10) )

Going from 20 to 40 miles runs 22.0, 24.2, 26.6, 29.3, 32.2, 35.4, 39.0, then a capped 40.0 - eight weeks. Because it compounds, the increments grow: week one adds 2 miles, week seven adds 3.5. Any doubling takes the same 7.3 weeks rounded up to 8, whether you are going 15 to 30 or 50 to 100.

Working with the plan

The unit does not matter. Kilometres compound identically - the tool only ever multiplies.
Spread the increase over existing runs rather than adding it all to the long run. A long run beyond about a third of weekly volume is where most people get hurt.
Target must exceed current or the tool refuses, and the projection stops at 104 weeks.

Two honest caveats. There are no step-back weeks in this projection: most coaches cut volume by 20-30% every third or fourth week, which adds two or three weeks to an eight-week ramp and is worth doing. And the 10% rule itself is a rule of thumb, not a finding - a randomised trial of 532 novice runners in 2008 found a graded 10%-style build produced the same injury rate as a standard programme. Below about 15 miles a week the percentage is too small to be meaningful, and above 60 it can be too aggressive. General information, not medical advice.

Frequently asked questions

What is the 10 percent rule in running?

Do not raise weekly mileage by more than 10% over the previous week. It is a brake on the enthusiasm that follows a good month.

How long does it take to go from 20 to 40 miles a week?

Eight weeks at a strict 10%, or about eleven once you build in a recovery week every fourth week. Doubling any weekly volume takes the same eight weeks.

Can I increase mileage faster than 10 percent?

Runners returning to a level they have held before often can, because the tissue adaptation is already there. Anyone building past their previous maximum should go slower, not faster.