Weekly Mileage Ramp Calculator
What the ten percent rule actually does when you follow it — it doubles the mileage in seven weeks and multiplies it by 142 in a year.
This is arithmetic on a rule of thumb, not training advice. The ten percent rule is a ceiling on any single step, and it says nothing about down weeks, injury history or what your body will tolerate — all of which matter more than the number. Nothing is uploaded.
Ten percent a week is not a modest increase
It compounds, and compounding is not what "ten percent" sounds like. It doubles the mileage in 7.3 weeks, triples it inside a training block, and over a year multiplies it by 142. From 20 miles a week that is 2841 miles a week by next August.
| After | Weeks | Multiple | From 20 miles |
|---|---|---|---|
| A month | 4 | 1.46× | 29 miles |
| Two months | 8 | 2.14× | 43 miles |
| A training block | 12 | 3.14× | 63 miles |
| Half a year | 26 | 11.92× | 238 miles |
| A year | 52 | 142.04× | 2841 miles |
The first row is why the rule sounds reasonable: over a month it is 1.46×, which is genuinely modest, and a month is the horizon most people picture when they hear it. The rule is a sane ceiling on a single step and nonsense as a trajectory, and the difference between those two readings is the difference between a rate and a plan.
Every weekly rate is exponential, including the cautious ones
Three percent a week sounds like nothing at all and still doubles the mileage inside six months. That is the shape of the thing: there is no weekly percentage small enough to be linear, only rates whose absurdity arrives later.
| Weekly increase | Doubles in | After 12 weeks | After a year |
|---|---|---|---|
| 3.0% | 23.4 weeks | 1.43× | 5× |
| 5.0% | 14.2 weeks | 1.80× | 13× |
| 7.5% | 9.6 weeks | 2.38× | 43× |
| 10.0% | 7.3 weeks | 3.14× | 142× |
| 15.0% | 5.0 weeks | 5.35× | 1433× |
Which suggests running the question backwards instead. Pick where you want to be and how long you have, and the rate falls out: getting to half again as much over a twelve-week block needs 3.4% a week, not ten. The doubling time does not depend on where you start, so this is the same arithmetic whether you are on twenty miles a week or eighty.
How to use
- Enter your current weekly mileage and the weekly increase.
- Set how many weeks you plan to hold it.
- Read the multiple, not just the miles.
- Or enter a target and get the rate it needs.
Frequently asked questions
What is the ten percent rule?
A common ceiling on how much to add to weekly mileage at a time. As a limit on a single step it is sensible. The trouble is that it is a compounding rate, and almost nobody reads it as one.
How fast does ten percent a week compound?
It doubles the mileage in 7.3 weeks, triples it in twelve, and multiplies it by 142 over a year. Twenty miles a week held at ten percent for a year is 2,841 miles a week, which is roughly a marathon a day and then some.
Why does it sound so reasonable then?
Because over the horizon people actually picture, it is reasonable — a month of it is only 1.46 times. The rule is a sane ceiling on a step and nonsense as a trajectory, and the two readings are easy to confuse.
Is a smaller rate safe from this?
No rate escapes it. Three percent a week sounds like nothing and still doubles the mileage inside six months. There is no weekly percentage small enough to be linear — only rates whose absurdity arrives later.
What should I do instead?
Run the question backwards: pick where you want to be and how long you have, and let the rate fall out. Reaching half again as much over a twelve-week block needs about 3.4% a week, not ten.
Does the starting mileage change the maths?
Only the miles, never the multiple. The doubling time is identical whether you are on twenty miles a week or eighty, because a percentage increase has no memory of where it started.
Is this training advice?
No — it is arithmetic on a rule of thumb. It says nothing about down weeks, injury history, surfaces or what your body tolerates, all of which matter more than the number. Take it as a way to see what a rate implies.
Does this send anything anywhere?
No. Every figure is computed in your browser, and nothing is uploaded or stored.
🔒 This tool runs entirely in your browser. Nothing you enter is uploaded, logged, or stored.