Marathon Pace Calculator

How to use this calculator

Choose between two modes: Calculate pace if you know how fast you want to run and need your finish time, or Predict from race if you have a recent race result and want to know how that translates to a different distance.

Calculate pace mode

Select your target distance, enter your goal pace in minutes and seconds per kilometre or mile, and the calculator will show your predicted finish time along with checkpoint splits so you know exactly where you should be at key points in the race.

Predict from race mode

Enter a recent race result — any distance from 5K to marathon — and select the distance you want to predict. The calculator uses the Riegel formula (T2 = T1 x (D2/D1)^1.06), the same method used by Runner's World and most serious race prediction tools. It accounts for the natural slowdown in pace as distance increases.

Understanding your splits

Splits show your predicted time at key checkpoints. For a marathon, you will see your expected time at 5K, 10K, the halfway point, 30K, and the finish. Use these as reference points on race day — if you are running significantly ahead of your split times in the first half, you may be going out too fast.

How accurate is the prediction?

The Riegel formula is well-calibrated for distances from 5K to half marathon. For full marathon predictions, accuracy depends heavily on your training mileage. Runners who have trained specifically for the marathon will often perform closer to the prediction; those stepping up from shorter distances may find the actual time is 5 to 15 minutes slower than predicted.

Common race distances

5K = 5 kilometres · 10K = 10 kilometres · Half marathon = 21.1 kilometres (13.1 miles) · Marathon = 42.2 kilometres (26.2 miles)