Burn

There is no direct way to measure your TDEE (total daily energy expenditure, how many calories you burn in the course of a day). There are wearable devices (Apple watch, Fitbit, Garmin smartwatch, etc) that will estimate it based on a bunch of algorithms - typically you have to set up a profile associated with your device that includes your sex, height, weight, age, maybe other stats like body composition, and the device uses those values in combination with data from an onboard accelerometer and/or pulse meter to do a bunch of math and spit out a number. People way smarter than I am have developed these algorithms and the devices that use them, so on average they're probably okay in terms of accuracy, but there's plenty of folks here who have trouble with their Fitbits et al over/underestimating their calorie burns. The only real recourse you have if you have a wearable and the estimates it gives you are not accurate is to figure out how inaccurate they are and in what direction, and mentally compensate for that, as far as I'm aware. There's no way to "recalibrate" your device.

You can use a calculator like the one at tdeecalculator.net to estimate your TDEE; that particular calculator is more accurate if you know your bodyfat percentage, but it's still pretty close if you don't. It's important to note that MFP calculates your calorie budget using a different method than the TDEE calculator. TDEE includes purposeful exercise if you do that as part of your daily activities, but MFP's method does not. MFP's method is based on NEAT - non-exercise activity thermogenesis, how active you are day-to-day without counting the time you spend exercising on purpose. If you use MFP the way the site intends, if you do any purposeful exercise in a given day, you'll log that in your diary and eat back the "extra" calories you burned exercising, because MFP has already given you a calorie goal that factors in (1) your general activity level and (2) the deficit required to lose weight. You can also, as I've done, figure out your TDEE and manually set your calorie budget to TDEE - 500 (for 1lb/week loss), and not log exercise.

You have been asking how many calories you should eat for a few weeks in many threads. I can see you've tried (random?) various numbers, and also calculated the amount to lose 1lb or 2lbs per week. You keep changing and I don't think you're giving it enough time to assess whether it's the right amount for you.

I strongly suggest you use the MFP set up, enter your weight, activity level ignoring exercise and a reasonable goal (lose 1lb per week) and eat what MFP tells you plus at least half of your exercise calories for a few weeks.