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.
Are Chicago and NYC Qualifying Times Fair by Age?
NYC's women's standard gets easier almost every five years from 35 to 79. Its men's standard barely moves. Same bracket rule, two very different curves.
PRs by Age Group, Explained With My Own Races
My 10 mile cell says 59:54 in one mode and 1:00:08 in the other. The slower race is the better one, and that gap is the whole point of the page.
Targets to Beat, Explained With My Own Races
A 36:31 10K says I could run a 17:31 5K and a 2:53 marathon today. Two of my eight road distances are within reach, and one of them shouldn't count.
Boston's New Downhill-Course Penalty, Age-Graded
A flat 3:05:00 age-grades to 66.6%. On a steep enough downhill course, the same nominal standard now needs 70.4% to actually clear it.
Are Boston Marathon Qualifying Times Fair by Age?
A 44-year-old's BQ time age-grades to 68.9%. A 40-year-old's identical time age-grades to 66.6%. Same bracket, same standard, different race.
Why Your parkrun Age Grade Is a Number You Can't Check
Your Saturday percentage and your race percentage will never agree. What parkrun's number is, what it isn't, and why the course underneath it matters more.
Why Every Age-Grade Calculator Gives You a Different Number
You cross-checked two calculators and got two scores. Neither is broken — they run different editions of the same tables. Here is my own race through all three.
No, Age Grading Isn't a Participation Trophy
The most common dismissal of age grading is that it's a consolation prize. The arithmetic says the opposite — it runs a deficit against measured decline for 26 years.
Older, Injured, and Chasing a Marathon Age-Grade PR at 48
Aging brought a knee injury that took a year to name. My absolute PRs may be gone — but an age-grade PR is the record you can still chase, and getting older nudges it closer.
The Problem With 5-Year Age Groups (What One Number Fixes)
A 50-year-old runs 38:00. A 54-year-old crosses 75 seconds later, same bracket — and outperforms him on age grade. The bracket has always hidden this.
What 80% Age Grade Looks Like, 5K to Marathon
A M50 hits 80% with an 18:15 5K. A W65 does it with a 3:39 marathon. The full 80% target table, by sex and single year of age — no calculator needed.
Why NYC Marathon Age Grades Differ From the Official Page
You ran 76.4% by the official results and 74.9% by RaceRecords. Same time, same age. The gap is one world record, not a bug — here's the exact math.
The 10 Greatest Masters Marathons, by Age Grade
A 59-year-old running 2:27:52 age-grades to a 2:01 marathon. The ten masters performances that press hardest against the open-class ceiling, men and women.
Where Masters Runners Are Fastest, by Country
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.
Why a World Record Can Age-Grade Below 100%
Clare Elms set a W60 1500m world record at 62. It grades 98.9%, while two road races that spring scored above 100%. The record was her weakest number.
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.
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