# RW’s Race Time Predictor

The Runner’s World race time predictor does exactly what it’s title suggests – this calculator lets you input a recent race time, to see what you should be capable of at another distance.

How does the race time calculator work?

It’s based on a formula originally devised by Pete Riegel, a research engineer and marathoner, and has been widely used for over 20 years. The formula is T2 = T1 x (D2/D1) 1.06 where T1 is the given time, D1 is the given distance, D2 is the distance to predict a time for, and T2 is the calculated time for D2.

It is adjusted for distance, so your 10K time prediction isn’t just double your 5K time, but there are things to note before using the calculator:

1. It assumes you’ve done appropriate training for the distance. Just because you’ve done a 22-minute 5K today doesn’t mean you can do a sub-4 marathon tomorrow. Obvious, really.
2. It assumes you don’t have a natural significant bias towards either speed or endurance. Some people, no matter how much training they do, will always over-achieve at one end of the scale.
3. The calculations become less accurate for times under three and a half minutes, and over four hours.

 Recent race length (you can use a decimal point, eg. 26.2): kilometresmiles My time (hours:minutes:seconds): : : Please estimate my time for: kilometresmiles Predicted time (hours:minutes:seconds): : :

I want to run faster, what should I do?

When it comes to running faster, we’ve got the training plans to help. Find the plan for you here:

Related: 5 reasons you can't run faster

5K training plans

10K training plans

Half-marathon training plans

Marathon training plans

How should I prepare for race day?

1. Nutrition: It goes without saying, fuelling your body properly will help improve your performance. Covering diet, hydration, recipes and supplements, take a look through our nutrition guide here.

2. Tapering:  Tapering is important when it comes to getting your body ready for race day, but it is anything but easy. Race-day nerves will increase, as the miles decrease, and it’s easy to feel jittery. Read up on how to taper, and avoid tapering mistakes here:

Related: How to avoid the top 4 tapering mistakes

Related: The importance of taper nutrition

3. Training: From motivational stories to keep your legs moving, to specific advice for every distance, have a browse through our training articles to find the answers to the most commonly asked questions, or the inspiration to head out on a particularly difficult run.

How should I recover post-run, or post-race?

1. Stretching: Post-race, you’ll need to make sure you’ve stretched your muscles to avoid injury. Have a look at our complete guide for stretching for runners to keep you flexible in all your main running muscles.

2. Recovery: Post race, or post run, you’ll need to make sure you’re getting enough rest to help your body recover and avoid injuries.

Related: 8 things you should always do to recover faster