Weekly Mileage Build-Up Calculator

About this calculator

Building weekly running mileage safely is governed by a widely cited but often oversimplified guideline — the '10 percent rule' — that caps how fast total weekly distance should rise so tendons, bones and connective tissue can adapt at the same pace as cardiovascular fitness. A proper build-up plan spaces steady increases with periodic recovery (or 'step-back') weeks, typically every third or fourth week, where mileage drops 15-20% before resuming the climb, rather than a straight uninterrupted ramp to peak volume.

Run coaches and self-coached marathoners use a structured build-up when returning from a break, moving up in race distance, or preparing a multi-month base-building block ahead of a training cycle, because uncapped week-over-week jumps in volume are one of the best-documented predictors of overuse injuries like stress fractures and tendinopathy. Capping the percentage increase and forcing in recovery weeks keeps the ramp aggressive enough to build fitness without outrunning the body's adaptation rate.

This calculator takes your current weekly mileage, your peak target and a maximum percentage increase per week, and returns a full week-by-week build-up plan with recovery weeks built in.