Use the Mifflin-St Jeor formula
For men: BMR = 10 × weight in kg + 6.25 × height in cm – 5 × age in years + 5
For women: BMR = 10 × weight in kg + 6.25 × height in cm – 5 × age in years – 161
Convert weight to kilograms if needed
Convert height to centimeters if needed
Plug in your age, weight, and height
Calculate the result to get your BMR in calories per day
Use an online BMR calculator if you want a quick result
Use a body composition test or metabolic test for a more precise measurement