Have a race coming up but unsure of your current ability? Or are you debuting at a new distance and don’t know what to expect? Instead of going too hard and bonking early, you can use our race time predictor to figure out an appropriate goal.

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What This Race Time Predictor Tool Does

Use this calculator to predict your estimated time and pace for any popular running race distance from 1500 meters to the marathon. For best results, your recent races should have a similar difficulty level (hills, surface, heat, etc.) as the race for which you’re predicting a time.

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Why Use This Race Time Predictor

Estimating your finish time is a major part of race prep—and not just so you can make sure you’re tracking for a PR.

How to Use The Race Time Predictor

Insert a recent race time into a field, and the tool will use an algorithm to predict your outcome for your target distance.

Note: This prediction tool becomes increasingly important as your race distance increases. Undershooting your 5K by five minutes probably won’t affect your life too much (unless you’re striving for a PR—in which case, we feel you), but underestimating your marathon time can really, really suck. Take it from Hollis Tuttle, RRCA-certified running coach and trainer for the Mirror, who learned this the hard way: “I didn’t have enough fuel, so I bonked about 3 miles out from the finish,” she says. “It was horrible.”

Plan out your races

As you plan out your races for the summer and fall, having a realistic goal in mind based on your previous race times is a great starting point when it comes to crafting the right training and racing plan.

“Your approximate finish time determines everything about your race plan,” says Tuttle.

This includes important things, like wearing the appropriate layers for a change in weather. “You should know if you’ll be running through the afternoon when it heats up,” Tuttle says, along with more upbeat action items, such as crafting the perfect playlist and planning your post-race brunch.

“Your cheer squad will be able to anticipate where you’ll be when, including when you cross the finish line,” Tuttle says. As for that playlist: “You’ll want to hear your favorite songs during the last quarter of the race when your energy starts to wane.” It’s a lot harder to make this happen without a sense of timing.

Most importantly, you need to plan your fuel accordingly. “Carbohydrate recommendations are based on how much time you spend running,” says Jessica Chon, R.D., which means not having a time estimate puts you at risk of messing up your food supply.

Chon says you should have 30 to 60 grams of carbohydrates every hour if you’re running 1 to 2.5 hours. (Your body has enough fuel to sustain you for runs less than an hour.) “And if you’re running for longer than 2.5 hours, that goes up to about 90 grams of carbohydrates per hour,” she says. “The more you run, the more you need to rely on external additional sources for energy.”

Now that you know how to properly prepare for your next race, get out there and start training! If you ever have a problem determining your next goal, use our race time calculator for the solution.

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Robert James Reese

Robert is the former Executive Producer for Runner’s World Online. He has run over 60 marathons with a personal best of 2:52:11. 

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Kiera Carter has a decade's worth of experience covering fitness, health, and lifestyle topics for national magazines and websites. In a past life, she was the executive digital editor of Shape and has held staff positions at Fit Pregnancy, Natural Health, Prevention, and Men’s Health. Her work has been published by Marie Claire, Cosmopolitan, Travel + Leisure, and more. She spends her free time boxing, traveling, and watching any movie or show with a strong female lead. She is currently based in New York.