Know Your Calories to Lose Weight or Build Muscle


To determine how many calories you need to lose weight or build muscle you first need to determine you basal metabolic rate (BMR, Harris Benedict Equation) . This is simply the amount of calories you need to survive with no physical activity ie laying in bed all day.

This is a formula based on your gender, age, weight & height. There is a calculator here.

Once calculated you then multiple this by a factor based on your activity level.

Little to no exercise 1.2
Light exercise (1–3 days per week) 1.375
Moderate exercise (3–5 days per week)  1.55
Heavy exercise (6–7 days per week) 1.725
Very heavy exercise (twice per day, extra heavy workouts)  1.9

This is your base number of calories to maintain your current body weight. In order to lose weight you need to consume less calories than your base (300-500) and to gain weight you need to consume additional calories above your base rate (200-300).


Male, 25, 5ft 10in, 80kg

His BMR is 1887 calories. Exercising 5 days per week his base calories are 2925 per day.
If he wishes to lose weight he needs to consume less than 2925  (1887 x 1.55) so he should aim for roughly 2625 per day. If he wishes to gain weight he needs to consume above this amount and should aim for roughly 3225 calories per day.

References – Michael Kory Fitness



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