BMR, TDEE, and what this calculator estimates

Your Basal Metabolic Rate (BMR) is the number of calories your body burns at complete rest just to keep you alive: breathing, circulating blood, repairing cells, and keeping your temperature steady. Your Total Daily Energy Expenditure (TDEE) is the bigger number that includes everything else you do, from walking and working to exercising. TDEE is the figure most people want, because it estimates how many calories you need each day to stay at the same weight.

This calculator uses the Mifflin-St Jeor equation, published in 1990 and widely regarded as one of the more reliable formulas for estimating BMR in healthy adults. For men it is BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age + 5. For women the final number is −161 instead of +5. Your BMR is then multiplied by an activity factor to give your TDEE.

The activity levels explained

The multipliers are 1.2 for sedentary (little or no exercise), 1.375 for light activity (1 to 3 days of exercise a week), 1.55 for moderate activity (3 to 5 days), 1.725 for active (6 to 7 days), and 1.9 for very active (a physical job or hard training twice a day). People often overestimate their activity, so if you are unsure, choose the lower of two levels. Remember that a desk job with a few workouts a week is usually "light" or "moderate", not "active".

A worked example

Take a 30-year-old man who is 175 cm tall and weighs 70 kg. His BMR is 10 × 70 + 6.25 × 175 − 5 × 30 + 5, which is 700 + 1,093.75 − 150 + 5, or about 1,649 calories a day. With moderate activity (1.55), his TDEE is about 2,556 calories a day.

Now take a 30-year-old woman who is 165 cm tall and weighs 60 kg. Her BMR is 600 + 1,031.25 − 150 − 161, or about 1,320 calories a day. At the same moderate activity level, her TDEE is about 2,046 calories a day. Age matters too: for the same man, being 40 instead of 30 lowers his BMR by 50 calories a day.

Using your result

The TDEE shown is a maintenance estimate. People who want to lose weight usually aim for an intake somewhat below it, and people who want to gain weight aim somewhat above it. A common rule of thumb is that a daily gap of around 500 calories leads to roughly half a kilogram of change per week, but real results vary a lot from person to person. Very low calorie intakes should only be followed under medical supervision.

Because this is a formula and not a lab test, your real needs could differ by a few hundred calories either way. The best approach is to treat the number as a starting point, follow it for two to three weeks, watch how your weight actually changes, and adjust from there. Muscle mass, hormones, medical conditions, pregnancy, and some medicines all change energy needs, so speak to a doctor or registered dietitian for personal advice. This tool gives general information only and is not medical advice.