Blog
The maths behind every percentage.
Field notes on age grading, distance bias, and what your race results actually tell you. Sourced, opinionated, no fluff.
Where Do Masters Runners Thrive?
Same race, same finish line — but the fastest 50+ runners come from entirely different countries than the fastest 25-year-olds. Here is why.
Why Your Marathon AG% Is Lower Than Your 5K
Same engine, same training block, six points apart. Why the marathon score is structurally harder to hit, and what the size of the gap tells you.
Equivalent Times Explained: Riegel's Formula
Two runners, same 44:00 10K, same age. One is predicted 3:22 for the marathon, the other 3:39. The difference comes down to one number derived from their race history.
When a World Record Falls Short of 100%
Clare Elms ran a W62 1500m world record at 98.91%. Her two spring road bests both scored above 100%. Here's what the gap between a record and the model's ceiling actually tells you.
I Age-Graded 100,807 Berlin Marathon Finishers
My 2023 Berlin result graded 78.73%. But what does a normal number mean? I graded all 100,807 finishers by age and sex to find out.
What Your Age-Graded Percentage Means
Two runners finish a 10K minutes apart. Age grading tells you who actually ran better — here is the formula and what the score means.