StrideForever · free running tools
Know your
pace. Master
your race.
Six fast, accurate running calculators — pace, race predictions, splits, training zones, treadmill conversion and WMA age grading. No sign-up, no fluff.
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See all 6 →Running Pace Calculator
Calculate your running pace per km and per mile from any distance and time. Free, instant pace and speed calculator.
Open 02Race Time Predictor
Predict your race finish time for 5K, 10K, half and full marathon from a recent result using the Riegel formula.
Open 03Age Grading Calculator
Calculate your WMA age-graded percentage and age-graded time for 5K, 10K, half marathon and marathon by age and sex.
OpenBuilt for runners, not for sign-up forms.
Genuinely free
No account, no paywall, no trial. Supported by ads — never by your wallet.
Accurate by design
Age grading uses the official WMA tables; race predictions use the proven Riegel formula.
Fast & private
Every calculation runs in your browser. Nothing to install, nothing stored.
Guides
Learn the numbers
What Is Age Grading? A Runner’s Guide to Age-Graded Scores
How age-graded percentages let a 25-year-old and a 70-year-old compare performances on a level playing field — and what your score actually means.
Read guideHow to Calculate Your Running Pace (and Actually Use It)
Pace is the number every runner lives by. Here’s how to calculate it, convert it to speed, and turn it into race splits and training zones.
Read guideRace Time Prediction Explained: Using the Riegel Formula
How a single recent result can predict your 5K, 10K, half or marathon time — and why the Riegel formula’s 1.06 fatigue factor matters.
Read guideEven vs Negative Splits: How to Pace Your Race
The difference between even, negative and positive splits — and how to plan the splits that stop you blowing up in the second half.
Read guideReady to run the numbers?
Explore all calculators →New to the numbers? Read the guides