Calorie burn is a complex calculation based on many factors, including age, sex, body weight, intensity and genetic factors. Rough estimates put calorie burn for punching a heavy bag between 462 and 500 calories per hour for men and 371 and 413 calories for women, depending on weight. Since punching bag workouts can vary greatly in duration and intensity, your best bet for tracking calorie burn is to wear a fitness tracker with a heart rate monitor.
In Fifteen Minutes
The average man weighs around 168 pounds in his 20s, 179 in his 30s and 182 in his 40s. The heavier you are, the more calories you burn in your workout -- about 2.75 calories per pound per hour when working out on the heavy bag.
This means that a 15-minute heavy bag workout would burn about 115 calories for a man weighing 168 pounds, nearly 123 calories for a man weighing 179 pounds and 125 calories for a man weighing 182 pounds.
Women tend to weigh less than men, with the average female's weight around 135 in her 20s, 143 in her 30s and 150 in her 40s. The average calorie burn is still 2.75 per pound per hour, so a woman of average weight for her age would burn between 93 and 103 calories in 15 minutes of punching a heavy bag.
In Half an Hour
A workout of half an hour on the heavy bag for a man of average weight for his age should burn between 231 and 250 calories. For a woman of average weight for her age, the same 30-minute workout would burn 186 to 206 calories.
Of course, the longer the workout goes on, the more likelihood that you will lower the intensity whether consciously or not. These numbers only apply if you are able to maintain a consistent level of intensity throughout your workout.
In Forty-Five Minutes
In 45 minutes punching a heavy bag, men of average weight will burn between 347 and 375 calories. For women of average weight, the same workout would burn between 278 and 309 calories.
However, it's highly unlikely that a person would punch a bag for 45 minutes straight. More than likely, a punching bag workout consists of spurts of high-intensity punching alternated with periods of rest or lower-intensity activity. In this type of interval training, the calorie burn could be less, equal to or even greater than the estimates for a steady intensity heavy bag workout.
Other Boxing Workouts
Boxing involves a lot more than just hitting a heavy bag, so if you train at a full-service boxing gym your calorie burn will vary depending on what other activities you are doing. Besides the heavy bag workout, you may also be working on the speed bag, jumping rope and sparring with other boxers.
All of these activities combined could burn around 800 calories in an hour, which is much more than you could burn by working with a heavy bag alone. Also, a more varied workout reduces the chance of developing repetitive stress injuries from continuously repeating the same high-impact moves.