how to know how much does your body burns calories exactly?

[ryuken]

i always had an extremely fast metabolism and i know that because i tried eating a lot of unhealthy foods for months but there wasn't a noticeable difference. is there a way to know how much does your body burn? even if it was medical tests just tell me

 

[chinprojectiongod]

eat 2500 calories for 1 year and do not move at all (literally remain completely sedentary) however much weight you gain/lose will tell you how many calories you burn

 

[Gonefishing]

Base Metabolic Rate -https://www.calculator.net/bmr-calculator.html

Calorie Calc-
https://www.calculator.net/calorie-calculator.html