Race Time Predictor
Race Time Predictor
Wondering what your 10K time says about your marathon potential, or what pace you'd need for a half marathon PB? This calculator gives you an honest, physiology-based answer — built on the same VDOT model used by coaches worldwide, not a rough guess dressed up as maths.
I'm Steve, an England Athletics qualified running coach (CiRF/LiRF) based in Manchester, and I built this tool for exactly the question runners ask me most: "if I can run this, what could I run over that distance?" Enter one recent race result below and you'll get an instant equivalent time across 5K, 10K, 15K, 10 Mile, Half Marathon and Marathon — from first steps to finish lines.
What could you run next?
Enter one recent race result and I'll estimate your equivalent time across every other distance, based on your current fitness — not a flat conversion factor.
Enter a recent race result and hit "Predict my times" — your VDOT fitness score and equivalent times will appear here.
Predictions assume you carry your current fitness across distances with appropriate race-specific preparation (long runs for the marathon, speedwork for the 5K, etc). They're a strong planning guide, not a guarantee — pacing, terrain, weather and taper all still matter on the day.
How does the race time predictor work?
This tool uses the VDOT method, developed by exercise physiologist Jack Daniels and used throughout distance-running coaching. Rather than simply multiplying your time by a fixed number (which badly overestimates marathon performance for most runners), it calculates your current running fitness from your race result, then works out the time you'd run at any other distance at that same level of fitness. That's why it stays accurate whether you're predicting a 5K from a marathon or a marathon from a 10K.
Why your predicted time isn't guaranteed
A prediction is a starting point, not a promise. It tells you what you're capable of at your current fitness — hitting it on the day still depends on race-specific training. A strong 10K doesn't automatically transfer to a strong marathon without the long runs and fuelling practice to back it up, and a fast 5K needs speed and leg turnover a marathon block won't build on its own.
If you'd like a training plan built specifically to close that gap — whether that's your first Couch to 5K, a marathon debut, or chasing a long-standing PB — take a look at bespoke training plans or online coaching, or just get in touch for a free, no-pressure chat.
Race time predictor FAQs
How accurate is a race time predictor?
It's a strong guide rather than a guarantee. VDOT-based predictors like this one are generally accurate to within a few minutes for a marathon and closer still for shorter distances, provided you train appropriately for the target race. Predictors tend to overestimate marathon performance most for runners who haven't built the endurance-specific training (long runs, fuelling, pacing discipline) that distance demands.
Can I predict my marathon time from a half marathon or 10K?
Yes — enter either result and you'll get an equivalent marathon time alongside every other distance. Just bear in mind the marathon prediction assumes you've also put in marathon-specific training, since a fast half or 10K alone doesn't guarantee the endurance to hold that fitness for 26.2 miles.
What is VDOT in running?
VDOT is a single number representing your current running fitness, developed by coach and exercise physiologist Jack Daniels. It's calculated from a race result and used to set accurate training paces and predict performance across other distances — it's one of the most widely trusted methods in distance-running coaching.
Which race result should I use for the most accurate prediction?
Use your most recent race, ideally run within the last 4-6 weeks so it reflects your current fitness. If you have two recent results at different distances, add both — averaging the two gives a sharper estimate than relying on a single race.