Determining the number of calories your body uses daily is a fairly straightforward process. This number is the sum of your basal metabolic rate (or the number of calories your body burns at rest), plus additional calories you burn through non-exercise activities, plus additional calories you burn through exercise. If you don't exercise much, you can get a relatively accurate estimate of your daily calorie usage with the help of an online tool, such as the Active calorie calculator below. If you exercise regularly, you're better off using separate tools to calculate calories burned in workouts.
More: Use the Active BMR Calculator
To determine how many calories you use daily outside of exercise, fill in the fields in the tool linked to above and select "sedentary" for your activity level if you work at a desk or "light activity" if you have a physical job. When you get the result, divide it by 24. That's the average number of calories you burn per hour. Now multiply the number of calories you burn per hour by the average number of hours you exercise per day and subtract the product from your 24-hour total. The resulting number is the total number of calories you burn daily outside of exercise.
More: 5 Ways to Burn an Extra 200 Calories
Now find an online tool (there are many) that allows you to calculate calories burned through activity and use it to find out how many calories you burn through your average daily amount of exercise. Add this number to the total number of calories you burn daily outside of exercise. This is the total number of calories your body uses in a typical day.
How Many Calories Do You Need?
Suppose you're a 35-year-old female who's 5-foot-6, weighs 133 pounds, and works at a desk. When this information is entered into Active's calculator it spits out an estimate of 1,894 calories used per day. Dividing this number by 24 yields an estimate of 79 calories burned per hour.Now let's suppose you're a runner and you run 45 per minutes per day. (It doesn't matter if you exercise a lot more on some days and a lot less on other days. If you calculate averages, everything will balance out by the end of each week.) This means you need to subtract three-quarters of an hour's worth of inactive calorie burning from your 24-hour total. This results in an estimate of (1,894 – [79 x 0.75] =) 1,834 calories burned per day outside of exercise.
More: Who Burns More Calories: New or Veteran Runners?
Now you need to account for the calories you burn through those 45 minutes of running. If your average running pace is 9:30 per mile, then you burn roughly 5 calories per pound you weigh per hour, which comes to 498 calories every 45 minutes. Adding this number to your previous total gives you a final estimate of 2,332 calories burned per day. If your goal is to maintain your current weight and make sure your body is well fueled for your training, then this number also represents the number of food calories you should aim to consume daily.
As previously mentioned, it's impossible to hit any calorie target exactly. Even so, it is more likely that you will avoid eating too much or too little if you go through this exercise and thereby increase your dietary awareness.
More: How to Avoid Underfueling Without Overeating
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