Weekly Mileage Progression Calculator
Building running volume gradually is one of the simplest ways to reduce overuse injury risk, and the familiar 10 percent rule suggests raising weekly mileage by no more than about a tenth each week. This calculator projects that build for you. Enter your current weekly mileage, the weekly percentage increase you want to apply, and the number of weeks to project. It compounds the increase and returns your next-week mileage, the mileage at the end of the build, the size of the first week's increase, and the total mileage across the whole period. The percentage is editable, so you can model gentler builds or your own preferred rate.
Mileage progression formula
growth factor = 1 + percentage / 100
next week = current * growth factor
mileage after N weeks = current * growth factor^N
first-week increase = current * percentage / 100
Worked example: 20 miles with a 10 percent weekly increase gives next week = 22.00 miles and a first-week increase of 2.00 miles. After 4 weeks the projected mileage is 20 * 1.1^4 = 29.28 miles.
Building mileage safely
- The 10 percent rule is a guideline, not a precise law; the right rate varies by runner.
- Compounding means small weekly percentages add up quickly over a build.
- Plan recovery or down weeks; this projection assumes continuous growth.
- The same arithmetic works for weekly time or any volume measure.
- Listen to your body and adjust the rate if niggles appear.
Mileage progression: frequently asked questions
What is the 10 percent rule for running?
The 10 percent rule is a common guideline suggesting weekly running mileage should rise by no more than about 10 percent from one week to the next, to allow the body to adapt and reduce the risk of overuse injury. It is a rule of thumb rather than a precise law, and the right rate varies by runner.
How does this calculator project mileage?
It applies a weekly percentage increase repeatedly. Next week equals current mileage times (1 plus percentage divided by 100). Projecting several weeks compounds the increase, so the calculator shows the target mileage after the number of weeks you enter, the increase in the first week, and the total mileage across the build.
Can I use a percentage other than 10?
Yes. The weekly percentage is an editable input. Some runners use smaller increases, hold mileage steady, or schedule down weeks for recovery. Enter whatever weekly rate matches your plan; the calculator simply compounds it.
Should mileage increase every single week?
Most structured plans build for a few weeks then insert a lower-volume recovery week before continuing. This calculator projects continuous growth at a fixed rate, so treat the output as an upper guide and plan recovery weeks into your real schedule.
Does the rule apply to time as well as distance?
The same compounding arithmetic works for weekly training time or any other volume measure. Enter your current weekly figure in the same unit you want the projection in, whether miles, kilometres, or minutes.
Official sources
- U.S. Centers for Disease Control and Prevention: Physical activity basics.
- National Center for Biotechnology Information (PubMed): Training-load progression and running-injury literature.
Reviewed by the CalculatorHub team, edited by James Graham, 17 June 2026. See our methodology.