Predict a Half Marathon Time with 5K Time
How 3.1 miles can help you determine your pace for a longer race.
By Jeff Galloway
You’ve got a big event coming up—a half-marathon, or maybe even a full. Even if your only goal is to finish, you may still want to know how long you’ll be out there. If you’ve run a 5K this year, you can plug your time into an online “race time predictor” (like the one at runnersworld.com/predictor). These tools convert your 5K pace to the (slower) pace you should be able to keep for longer distances. Doing a 5K close to race day will give you the best picture of your current fitness.
WHEN TO DO A 5K Schedule a 5K the weekend before your last long run—three or four weeks from race day—in place of a long, slow effort. Look for a flat course and a field of no more than a few hundred runners. You’ll run your best at temperatures lower than 65 degrees Fahrenheit, so find an event with a morning start.
RUN A TEST You should use this event to test out your prerace meal and the clothes and shoes you’re planning to wear on the day of your longer event. Keep a controlled pace for the first half of the 5K, running very comfortably, and then gradually speed up to finish strong. This is also good practice for your goal race.
CALCULATE, ADJUST Race-time predictors reflect ideal conditions for experienced runners, so new runners need to adjust. First-timers, add between 1:30 and two minutes per mile to determine a comfortable pace. For example, if the calculator says you could race a half-marathon in 2:00, or at 9:10 pace, plan to go out at 10:40 to 11:10 pace. If it’s your second time and you’d like to push harder, add 45 to 60 seconds per mile. To adjust for heat, add 30 seconds per mile for every five-degree jump above 60 degrees.