How much the increase rate changes the timeline
When runners raise weekly mileage, the question that actually matters is not how much to add but how long the chosen rate takes to reach the target. This calculator takes this week mileage and a target weekly mileage, puts 5%, 10% and 15% weekly increases in the same table, and reports the week each one reaches the target. Enter last week mileage as well and it also shows the increase you actually made and where that sits among the three cases.
The figures compound the rate you entered, so they are arithmetic on an assumption rather than a forecast; real mileage rarely rises in a straight line. The week a target is reached is judged on the same single decimal shown in the table, so the table and the summary never disagree. Plans that reduce mileage and schedules with built-in down weeks are not supported. Written as of October 2026.
The familiar 10% rule has no randomised trial support behind it. In a trial with novice runners, a 13-week graded programme based on the rule produced an injury rate of 20.8% while a standard 8-week programme produced 20.3%, effectively the same. This page therefore produces no injury risk score or probability and only compares the arithmetic of the three rates. Persistent pain is a reason to see a clinician before adding distance.
FAQ
In a randomised trial with novice runners, a programme built on the 10% rule produced an injury rate of 20.8% against 20.3% for a standard programme. No preventive effect was shown.
Not to pick a safe one, but to see in numbers how much the time to a given target changes with the rate. No risk score is produced here.
At low rates a target can be dozens of weeks away and the table becomes unreadable. It stops at week 26 and the actual number of weeks is given in the results instead.