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What This 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.
Why Use It: 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.
“Your approximate finish time determines everything about your race plan,” says Hollis Tuttle, RRCA-certified running coach and trainer at Mile High Run Club in New York.
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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, RD, a nutrition specialist at Clif Bar & Company, 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.” (For context, one has 24 grams of carbohydrates.)
How to Use It: 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 Tuttle, 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.”
Speaking of PRs, it’s not too late to change this number if it’s slower than you thought. Here are 4 Sprint Workouts That Will Increase Your Speed. Tottle also emphasizes the benefits of hitting the weight room: “All runners should be strength training once or twice a week,” she says. “Lifting not only helps you avoid injury, but it allows you to run faster, longer.” We suggest trying these 9 Weight-Training Exercises for Runners or blast through a series of HIIT sessions to boost your strength with the IronStrength Workout.