According to Diet Health Club, the average person can burn 100 calories in about 1,000 regular sit-ups. That number can be increased by doing high-intensity sit-ups: However, Diet Health Club states that it is impossible to burn more than 270 calories in any half-hour session of sit-ups.
Diet Health Club says that the average 150 pound person burns 1 calorie with every 10 sit-ups. It is therefore possible to burn 10 calories for every 100 sit-ups completed. According to Diet Health Club, It may be possible to burn as many as 270 calories in a half-hour period; but this requires a fit athlete to complete approximately 2,700 sit-ups in a half-hour period.