Knowing your pace in minutes per mile can help you estimate how long it might take you to cover a specific distance. Most treadmill models will tell you how fast you are going in terms of miles per hour (mph), but won't tell you the equivalent minutes-per-mile pace. If you run a 5-mph pace on the treadmill, you will cover one mile in 12 minutes. You may not duplicate this pace if you run outdoors, however.
Treadmill Versus Outdoors
When you run outside, you must navigate over uneven terrain and work against wind resistance, so your speed is slightly misleading. The treadmill doesn't offer these challenges, so your session is slightly easier. The evenness of the treadmill belt means every time you plant your foot, it feels almost exactly the same -- so you don't have to work as hard making subtle adjustments for pebbles, divots and undulations. The belt also pulls you along instead of you having to push off against the ground as you do outdoors, so it may be easier for you to maintain an even pace on a treadmill.
Effect on Speed
When you go 5 mph on a 0 percent incline on your treadmill, the machine may log you going a mile in 12 minutes. If you took that same effort outdoors, however, you'd probably take longer to cover the mile because of the challenges of wind resistance and terrain. But, when you run outdoors, your rating of perceived exertion -- or self-determination of how hard of an effort you are putting forth -- changes, showed a seminal study published in a 1991 issue of the journal "Medicine and Science in Sports and Exercise." Runners were asked to set their own pace running outdoors and indoors on a treadmill and then to rate their perceived exertion. They ran significantly faster outdoors, despite reporting an equal feeling of effort in both runs.
If you can't head outdoors and want to make sure your 12-minute-mile, or 5 mph, pace is true, try setting the incline on your treadmill at 1 percent. An August 1996 issue of the "Journal of Sports Sciences" found that running on a 1 percent grade on the treadmill most accurately replicated the effort of running on a flat course outdoors. You can also increase the incline to a higher level if you are training to run outdoors on a hilly course.
If you can achieve your indoor 5-mph mile outdoors, you'll be able to finish a 5K, or 3.1 miles, in about 37 minutes and 12 seconds. A 10K, which is equal to 6.2 miles, will take you about one hour, 14 minutes and 24 seconds. If you can maintain the pace for 13.1 miles -- a half-marathon distance -- you'll be done in two hours, 37 minutes and 12 seconds.