Free running calculators

Run the numbers

Calculators for runners who race, or want to: predict what a recent result says about your next distance, then turn that goal into a pace and a split for every mile. No sign-up, no app, nothing to install.

• Race Time Predictor

  Turn a recent race into predicted 5K, 10K, half marathon and marathon times, from three models side by side.

• Running Pace Calculator

  Pace from a finish time, finish time from a pace, or distance from both, with speed and mile or km splits.

• VDOT Calculator

  Your Jack Daniels VDOT from a race, with easy, marathon, threshold, interval and repetition training paces.

• Treadmill Pace Calculator

  Treadmill speed to pace and back, in mph or km/h, with the flat-ground pace an incline is worth.

• Yasso 800 Calculator

  Your marathon goal as 800 m repeat times, with lap pace, recovery jogs and a build-up plan.

From one race to your next goal

The calculators are built to work together. Start with the race time predictor: enter a race you ran recently and it shows what that fitness is worth at another distance, using three published models so you can see how much they agree. Take the time you're aiming for to the pace calculator and it gives you the pace per mile or kilometer to hold, and the time you should see at each marker.

Everything runs in your browser. Your times never leave your device.

How accurate are the numbers?

Pace arithmetic is exact: distance, time and pace are tied together by simple division, and the calculators handle the minutes-and-seconds conversions that make it fiddly by hand. Race predictions are estimates. The models behind them (Riegel's formula, Cameron's model and Jack Daniels' VDOT) are fitted to real race results and agree closely between neighbouring distances, but they assume you've trained for the distance you're predicting. The predictor shows the range between models and flags long jumps, such as 5K to marathon, where the estimate is a best case.

Standard race distances

The distances the calculators use, in kilometers and miles. The half marathon and marathon are fixed by World Athletics at 21.0975 km and 42.195 km.