Calories out can't be directly measured, BUT you can compute it pretty accurately anyway. Measure your weight. Track your calorie consumption for N days, then

Calories out can't be directly measured, BUT you can compute it pretty accurately anyway. Measure your weight. Track your calorie consumption for N days, then measure your weight again. Then use the 3500 calories per pound conversion to figure out what calories out must have been to cause that. For example, if over 30 days you ate 2000 calories per day and lost 3 pounds, then you must have burned 3500 * 3 excess calories total. That averages out to 350 calorie deficit per day, so your calories out must have been 2350. Or if you ate 2000 calories per day for 30 days and your weight remained the same, then your calories out was 2000 as well. I've been calorie counting for a long time (initially to lose weight, now just habit), and I do this sort of calculation every month or two in order to maintain my weight within a ~5 pound range.