Race Predictor – Running Time Calculator

Created by Filip Derma and Aleksandra Zając, MD
Reviewed by Bogna Szyk and Steven Wooding
Last updated: Jun 05, 2023

Omni's race predictor is a helpful tool for all runners and athletes who want to develop their race results. Based on your previous running scores, our running time calculator will foresee the time for another run competition. Without complicated analysis, check quickly whether you are able to cover another distance at a satisfying time and running pace.

In the article below, you will find a short tutorial on how to use the calculator, a description of some aspects of training, and a few tips for preparing for race day.

Four runners in a running race

We try our best to make our Omni Calculators as precise and reliable as possible. However, this tool can never replace a professional doctor's assessment. If any health condition bothers you, consult a physician.

Running time – how to predict?

Calculations in our running time predictor are based on the mathematical formula published in 1977 in Runner's World Magazine. Peter Riegel, an American research engineer, and marathoner, devised the equation. The expression allows for the prediction of race times for runners and other athletes giving a certain performance at another distance. Over the years, the formula has been widely approved by the sports community thanks to its high calculation accuracy and simplicity in its application.

Riegel's formula:

T2=T1(D2D1) ⁣1.06T_2 = T_1 \left(\frac{D_2}{D_1}\right)^{\!1.06}


  • T1T_1 – Time achieved recently on distance D1D_1;
  • T2T_2 – Predicted time for distance D2D_2;
  • D1D_1 – Distance over which T1T_1 time was achieved; and
  • D2D_2 – Distance for which T2T_2 time is foreseen.

💡 You might also be interested in our marathon pace calculator.

Pete Riegel's formula assumptions

Before using the running time predictor, there are some points worth noting about Riegel's equation:

  1. It assumes that a runner has done appropriate training for the distance they want to run. A very good result on the 10 km distance a day ago doesn't mean that today you can run a half-marathon in 1 h 30 min.

  2. Assumes that an athlete doesn't have a significant natural tendency for either speed or endurance. Some people, no matter how much they train, will always have better results than others.

  3. The calculations are less accurate for times under 3.5 minutes and for times over 4 hours.

The great benefit of this formula is that it's adjusted for distance – it doesn't simply double, e.g., the 6 km prediction for 12 km prediction.

How to use race predictor?

To be sure you're using the running time calculator properly, let's go together through the example below:

  1. Fill in the distance of a recent race result: say it was a half marathon, D1=22 km\small D_1 = 22\ \rm km.

  2. Type the time which you have achieved on that distance: It was T1= 1h 57min 26s\small T_1 =\ \rm 1\,h\ 57\,min\ 26\,s - not bad!

  3. Choose the new distance you want to run: I like long runs! D2=30 km\small D_2 = 30\ \rm km.

  4. Prediction for new distance is equal to T2=2h 43min 8s\small T_2 =\rm 2\,h\ 43\,min\ 8\,s – quite a lot of sweating!

Want to be prepared for the race? Follow the training plan!

Being a faster runner is not a piece of cake. Many factors impact being in shape, like below:

  • Type of training;
  • Training intensity;
  • Nutrition;
  • Biological recovery; and
  • Health condition.

Keep in mind that 5 km, 15 km, half marathon races, or mountain runs have significantly different characteristics. For each of them, during training, you will need to focus on different aspects, e.g., endurance, speed, strength, or dynamics. It means that for each race type, you will need to follow a specific training plan to be able to keep a good running pace (see our running pace calculator for more help).

Race day preparation

End line of a running race

Your few weeks' race training is done. You did a good job! The race day is close ahead. Still, you should make sure you properly prepare for these memorable hours. Here are a few points to focus on:

  1. Nutrition – Refuel your body properly. Do not allow yourself to take a race with a lack of calories (see meal calorie calculator). You should think about a proper diet, hydration, and supplementation (vitamins, micro & macro elements).

  2. Recovery – Competition, when your body is tired after hard training, can't be good for you. Take care of biological regeneration.

  3. Mental power – Have freedom in your thoughts. Being seriously stressed doesn't bode well. Some meditation may help your mind to be clear.

  4. Warm-up – This might seems obvious, but don't forget about gradually warming your muscles and stimulating the cardiovascular system before starting.

Good luck!

Filip Derma and Aleksandra Zając, MD
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