1. First, you should know that the number you see on the treadmill and other gym equipment is probably wildly inaccurate.
2. And that's because the calories you burn depend on a lot of factors that the machines at the gym can't track.
3. Let's go over how your body burns calories. It's actually all about oxygen consumption.
4. There's an equation you can use to get a general sense of how many calories you burn during a workout.
5. But if math isn't really your thing, there are apps and wearables that will do the work for you.
6. The wearables that accurately track your heart rate are going to be the best at estimating the calories you've burned.
"If your goal is to be more mindful of being more active, than any of the fit technologies and websites will be useful," Milton says. "But if you're talking about accuracy of the device in telling you something specific about your workout such as heart rate or how far you've run, then that's going to determine the wearable you wear."
If you're trying to record calories burned for specific endurance exercises, like running or cycling, you need to accurately track your heart rate, and the best way to do that is with a chest heart rate sensor. Corey and Milton recommend the Polar H7 heart rate sensor, which has an adjustable strap and can be worn comfortably under your clothes.
Some other great options are Jawbone wearables for tracking heart rate, Garmin watches for tracking distance (because of the GPS), and Fitbit wristbands, which track heart rate as well as other areas of health that improve your quality of life.
Heads up, though: Trackers won't be as accurate if you're working out smaller muscle groups — like if you're doing bicep curls, for example. That's because the blood volume you're using is going to go up and your heart rate will go up, but it won't be burning as many calories because it's not a total-body expenditure, like running is.