Updated December 18, 2014.

Written or reviewed by a board-certified physician. See About.com's Medical Review Board.

"I'm hoping to lose weight with running. How many calories do I burn when I'm running?"

The amount of calories you burn during a run depends on numerous factors, the most important being your weight and level of exertion.

How Weight Affects Calories Burned
The more you weigh, the more calories you'll burn while running. A 140-lb person running at a 10-minute- mile-per pace (6 mph) will burn 318 calories in 30 minutes.

Running the same pace for the same amount of time, a 180-lb person will burn 408 calories.

How Speed Affects Calories Burned
The faster you run, the more calories you'll burn. A 160-pound person running at a 12-minute pace (5 mph) for 30 minutes would burn 290 calories. The same person running at a 10-minute-per-mile pace (6 mph) would burn 363 calories in 30 minutes.

How Many Calories You're Burning While Running
To get a rough estimate of how many calories you're burning based on your weight and speed, you can use a calorie expenditure calculator. There are also apps available that track your calories as you run. Keep in mind, however, that this is just a rough estimate of your calories. Treadmill calorie calculators in particular are often inaccurate and overestimate the number of calories burned during a run. Don't make the mistake of overindulging because you're overestimating the number of calories you're burning.

So, How Do I Lose Weight By Running?
If you're trying to lose weight by running, keep in mind that a pound equals 3,500 calories.

So you would need to create a 3,500 calorie deficiency with exercise or calorie cutting. A safe, healthy weight loss rate is about .5 to two pounds per week. If you lose weight faster than that, you may be losing muscle in addition to fat.

To reach the goal of one pound lost per week, you'd need to create a 500 calorie deficiency, either through exercise or calorie cutting, per day. You'd first have to figure out how many calories you need per day to maintain your weight. If you don't want to cut calories by eating, then figure out (using a calorie expenditure calculator) how much you need to run each day to burn 500 calories. To create a 500-calorie deficit by running, a 150-lb person, for example, would have to run for about 45 minutes at a 10-minute per mile pace.

Also see:
How Many Miles Per Week Should I Run to Lose Weight?
Does Running Outside Burn More Calories?
Common Weight Loss Mistakes
Why Am I Not Losing Weight With Running?

<sub>Sources: Ainsworth BE, et al. 2011 compendium of physical activities: A second update of codes and MET values. Medicine & Science in Sports & Exercise. 2011;43:1575.

Exercise Calorie Expenditures, accessed 4/1/2013</sub>