You can use a calculator or whatever - but here is the bottom line: the calories you burned can best be determined by the calories you take in vs. your weight.
Track everything you eat for a week. Weigh yourself every day so that you can at least be sure you don't have an unusual reading. Compare the calories you took in for the week vs. what your weight did over that week.
If you are exactly the same weight, you ate at maintanence. For every pound above your starting weight, you ate 3,500 calories/day on average above your maintenance. For every pound below, you ate 3,500 calories/day below.
Now, even this is not 100% accurate and the longer you spread this out (2 weeks, a month, a year) the more dialed in you could possibly get with it. But between that method and a calculator you can usually come up with an estimate pretty quickly and double check it yourself.