What are some scientific ways to measure calories burnt, and how exact they are?

After what I know of calories I burn my body daily work?

Now you can calculate true If the calories burned by your body in, for example, you can eat a day and be provided calories and you can also practice exercise to consume energy calories, for example, for a total that was lost that day calories and so will decrease your weight, God willing, the way ideal as there are a lot of studies have demonstrated the success of many of those who use this method to know and calculate calories with the observation that in order to diminish the weight of Kilwa and one must burn7, calories.