Weekly Mileage Buildup Calculator

About this calculator

The 10% rule is a widely cited guideline in running that caps weekly mileage increases at roughly 10% over the previous week, giving connective tissue, tendons and bone time to adapt to increasing load before injury risk climbs sharply. Applied over several weeks, it produces a gradually compounding curve — starting from a base mileage and increasing by 10% each week builds up faster than a flat linear increase, while still respecting the body's adaptation timeline.

Running coaches use mileage buildup plans like this when transitioning a runner from a lower training base toward marathon or ultramarathon volume, and also recommend periodic "cutback" weeks (reducing volume by 20-30% every third or fourth week) to allow additional recovery — something a rigid, uninterrupted 10% progression doesn't account for on its own. Overuse injuries like stress fractures, shin splints and tendinitis are strongly associated with mileage jumps that outpace the body's adaptation rate, which is exactly the risk this rule is designed to manage.

This calculator projects your weekly mileage over a chosen number of weeks using the 10% increase rule from your current starting point.