Calcylator
Calories

BMR and daily
calories, explained

How many calories your body uses at rest, and how activity changes the total.

Calcylator Editorial Team

Updated · 5 min read

What BMR and TDEE mean

Basal metabolic rate (BMR) is the energy your body uses at complete rest: breathing, circulation, keeping warm and repairing cells. It is measured in kilocalories per day (kcal/day), which is what most people simply call calories.

Total daily energy expenditure (TDEE) is BMR plus everything else you do in a day: walking, working, exercising and digesting food. TDEE is the figure to use for meal planning, because it estimates what you actually burn.

Both are estimates from a formula, not lab measurements. They make a useful starting point, not a prescription.

The Mifflin–St Jeor formula

The BMR Calculator uses the Mifflin–St Jeor equation, a widely used estimate of resting energy from weight, height, age and sex. Use kilograms, centimetres and years.

BMR (men) =10 × weight + 6.25 × height − 5 × age + 5
weight:
body weight in kg
height:
height in cm
age:
age in years
The result is in kcal per day.
BMR (women) =10 × weight + 6.25 × height − 5 × age − 161
weight:
body weight in kg
height:
height in cm
age:
age in years
Only the last constant changes: +5 for men, −161 for women.

  • Sex

    Male

  • Weight

    70 kg

  • Height

    170 cm

  • Age

    30 years

Estimated BMR

1,618 kcal/day

10 × 70 = 700, 6.25 × 170 = 1,062.5 and 5 × 30 = 150, so 700 + 1,062.5 − 150 + 5 = 1,617.5, rounded to 1,618.

For a woman who is 60 kg, 160 cm and 30 years old, the sum is 600 + 1,000 − 150 − 161 = 1,289 kcal/day.

The formula also shows how each input behaves. Every extra kilogram adds 10 kcal/day, every extra centimetre of height adds 6.25, and every year of age takes off 5. That is why BMR rises with body size and drifts down slowly as the years pass.

From BMR to TDEE: the activity multiplier

To estimate TDEE, multiply BMR by an activity factor. The TDEE Calculator offers the same five standard levels.

TDEE =BMR × activity multiplier
BMR:
resting energy from the formula above, in kcal/day
activity multiplier:
a factor from 1.2 to 1.9, chosen from the table below
Activity multipliers, with the TDEE for a BMR of 1,618 kcal/day (rounded to the nearest kcal)
Activity levelMultiplierTDEE (kcal/day)
Sedentary: little or no exercise1.21,942
Light: 1–3 days a week1.3752,225
Moderate: 3–5 days a week1.552,508
Active: 6–7 days a week1.7252,791
Very active: hard daily training1.93,074

Pick the level that matches a typical week, not your best one. If you are torn between two, start with the lower and adjust after a few weeks.

Our example man, moderately active, gets 1,618 × 1.55 = 2,508 kcal/day.

Turning TDEE into a daily calorie target

Eating around your TDEE tends to hold your weight steady. Eating below it creates a deficit, and eating above it creates a surplus.

  • For gradual weight loss, a modest deficit of a few hundred kcal is easier to keep up than a drastic cut. For the example above, 300 kcal less gives 2,508 − 300 = 2,208 kcal/day.
  • For gaining weight, a small surplus of a few hundred kcal is a reasonable start: 2,508 + 300 = 2,808 kcal/day.
  • Very low intakes are hard to sustain and can leave you short of nutrients, so they should only be followed under medical supervision.

It also helps to compare the target with what you eat now. Note down a typical week of meals using the calories on food labels; the gap between that and your TDEE shows how big a change you would really be making.

How far to trust the numbers

Mifflin–St Jeor describes an average person with your inputs. Muscle mass, genetics, health conditions and some medicines all change real energy use, and the formula cannot see them.

Treat the result as a starting point. Follow it for two to three weeks, watch your weight trend, and adjust in small steps rather than big jumps.

Body weight is one signal among many. The BMI Calculator adds a quick height-to-weight check, though it cannot tell muscle from fat.

Common questions

How do I calculate my BMR?

Use the Mifflin–St Jeor equation: 10 × weight (kg) + 6.25 × height (cm) − 5 × age (years), then add 5 for men or subtract 161 for women. A 70 kg, 170 cm, 30-year-old man gets about 1,618 kcal/day. The BMR Calculator does the sum for you.

What is the difference between BMR and TDEE?

BMR is the energy your body burns at complete rest. TDEE is BMR multiplied by an activity factor, so it includes movement, exercise and digestion. TDEE is the better guide for how much you can eat each day to keep your weight steady.

Which activity multiplier should I choose?

Use 1.2 if you mostly sit, 1.375 for light exercise one to three days a week, 1.55 for three to five days, 1.725 for six to seven days, and 1.9 for hard daily training. If you are between two levels, choose the lower one.

How many calories should I eat a day?

There is no single number. Start from your TDEE, which keeps weight steady, then adjust modestly for your goal. A doctor or registered dietitian can set a target that suits your age, health and lifestyle. Treat any calculator result as an estimate.

Is the Mifflin–St Jeor equation accurate?

It is a widely used estimate for healthy adults, but it is not exact. Muscle mass, health conditions and medicines can shift your real energy use. Use the result as a starting point and adjust based on how your weight changes over several weeks.

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