Race time predictor
Enter one recent race result and we'll project your finish times across the classic distances — 5K, 10K, half marathon and marathon — with the matching paces. It uses Riegel's endurance model, the same fatigue curve coaches use to set realistic goals.
Projected finish times
| Distance | Time | Pace |
|---|---|---|
| 5 km | 21:35 | 4:19 /km |
| 10 km | 45:00 | 4:30 /km |
| 15 km | 1:09:10 | 4:37 /km |
| Half marathon | 1:39:17 | 4:42 /km |
| Marathon | 3:27:01 | 4:54 /km |
Estimates from Riegel's model (exponent 1.06). Real race times depend on training, fueling, terrain and the day — treat these as a target range, not a promise.
A prediction is a number. Leo gets you there.
Coach Leo turns a target time into a week-by-week plan, anchored to your real Strava data and adjusted every week to how you actually feel.
Get started freeFree plan · no credit card
Everything about predicting your race time
Frequently asked questions
How does a race time predictor work?
It takes one performance you've already run and projects it onto other distances using a fatigue model. We use Riegel's formula: predicted time = known time × (new distance ÷ known distance) raised to the power 1.06. The exponent above 1 captures the fact that you slow down as distance grows.
How accurate is the prediction?
It's a solid ballpark for distances close to the one you entered, and most accurate when your training matches the target race. Predicting a marathon from a 5K tends to be optimistic — the marathon punishes anyone who hasn't built the specific endurance. Use a recent race at a similar distance for the best estimate.
What's a good recent result to enter?
An all-out effort from the last 4–6 weeks gives the truest picture. A hard 10K or half is ideal for predicting longer races; a 5K works well for shorter ones. Avoid using a casual training run — the model assumes the input was a real, near-maximal effort.
Do I need a race to predict my time?
Not with Coach Leo. The calculator here needs one result, but Leo's own race estimate is built from your training data alone — it reads your Strava history and updates a projection daily, no test race required.
Why does the marathon prediction look fast?
Pure-formula predictors don't know your long-run volume or fueling. The Riegel model assumes you've trained appropriately for the distance. If your weekly mileage and long runs aren't marathon-ready, add a realistic buffer — or let Leo factor your actual training load in.
What pace should I run on race day?
Start at or just behind your predicted average pace and aim for an even or slightly negative split. Going out faster than your prediction is the most common race-day mistake. The pace column above gives you the average pace each target implies.
Is this the same as a VDOT calculator?
It's in the same family. VDOT-style models map your performance to a fitness score, then read equivalent times off a table; Riegel goes straight from one time to another. They give similar answers for nearby distances. Leo blends these methods with your real training history for its own estimate.
How often should I re-check my prediction?
After any hard race or time trial, or every 4–6 weeks of focused training. Fitness moves; a prediction from three months ago is stale. With Leo it refreshes automatically as new runs sync.
Other tools