TDEE & Calorie Deficit Calculator – Maintenance and BMR

How do you calculate your daily calorie needs?

In two steps. First the calculator estimates your basal metabolic rate (BMR), the energy you would burn lying still all day. It uses the Mifflin-St Jeor equation, published in 1990:

Men: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age (years) + 5

Women: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age (years) − 161

Then it multiplies BMR by an activity factor. The result is your total daily energy expenditure (TDEE), the calories that would keep your weight stable:

Daily calories to maintain weight = BMR × activity factor

Strictly speaking, Mifflin and St Jeor measured resting energy expenditure, which is very close to BMR. Most calculators use the two terms interchangeably.

What is TDEE (maintenance calories)?

TDEE is the total energy you use in a day, and it is the same thing as your maintenance calories. Eat about that much on average and your weight stays roughly stable. TDEE stands for total daily energy expenditure. It is your BMR plus the energy for digesting food and for every kind of movement, from climbing stairs to a workout.

This calculator estimates TDEE as BMR × activity factor and shows it as Daily calories to maintain weight. It is an estimate for an average person with your numbers, so your real maintenance figure may sit a little higher or lower.

How to use the calorie calculator

Choose your Sex. The equation has a different constant for men and women.
Enter your Age in years, your Weight in kg and your Height in cm.
Pick the Activity level that best describes a normal week. The default is Light.
Under Goal, keep Maintain my weight, or choose Lose weight (500 kcal a day deficit) or Lose weight (750 kcal a day deficit).
Read the Daily calories to maintain weight, rounded to the nearest 10 kcal, and your Basal metabolic rate underneath. With a weight-loss goal the result is Daily calories to lose weight, and the maintenance figure moves underneath.

Worked examples

Example 1 – man, moderately active. 30 years, 70 kg, 175 cm, Moderate (3–5 days a week). BMR: 10 × 70 + 6.25 × 175 − 5 × 30 + 5 = 700 + 1,093.75 − 150 + 5 = 1,649 kcal. Daily needs: 1,649 × 1.55 = 2,556 kcal, shown as 2,560 kcal to maintain weight.

Example 2 – woman, lightly active. 45 years, 65 kg, 163 cm, Light (1–3 days a week). BMR: 10 × 65 + 6.25 × 163 − 5 × 45 − 161 = 650 + 1,018.75 − 225 − 161 = 1,283 kcal. Daily needs: 1,283 × 1.375 = 1,764 kcal, shown as 1,760 kcal.

Example 3 – older man, sedentary. 60 years, 85 kg, 178 cm, Sedentary (little or no exercise). BMR: 10 × 85 + 6.25 × 178 − 5 × 60 + 5 = 850 + 1,112.5 − 300 + 5 = 1,668 kcal (1,667.5 rounded). Daily needs: 1,668 × 1.2 = 2,001 kcal, shown as 2,000 kcal.

Example 4 – a calorie deficit. The woman from Example 2 chooses Lose weight (500 kcal a day deficit). Target: 1,760 − 500 = 1,260 kcal a day to lose weight. With the 750 kcal deficit the target would be 1,010 kcal, below 1,200 kcal, so the calculator would add a warning.

Activity factors

Activity level	Factor	What it means
Sedentary (little or no exercise)	1.2	Desk job, little walking, no planned exercise
Light (1–3 days a week)	1.375	Light exercise or sport on 1–3 days
Moderate (3–5 days a week)	1.55	Moderate exercise on most days
Active (6–7 days a week)	1.725	Hard exercise nearly every day
Very active (hard training or physical job)	1.9	Twice-daily training, or heavy manual work

These multipliers are a common convention, not part of the Mifflin-St Jeor equation, so they give a rough estimate. The gap between levels is large. For a BMR of 1,500 kcal, moving from Sedentary to Moderate changes the estimate from 1,800 to 2,325 kcal. Choosing the right level matters more than any decimal in the equation.

What does a calorie deficit mean?

A calorie deficit means taking in less energy than your TDEE. The body then draws on its stores, mainly fat, and weight falls over time. The bigger the gap, the faster the loss, but large deficits are harder to keep up and can cost muscle and nutrients.

Your TDEE is the starting point any deficit is measured from. Under Goal, the calculator subtracts 500 or 750 kcal a day, the deficits the 2013 AHA/ACC/TOS guideline uses for adults with overweight or obesity, and shows Daily calories to lose weight. It does not predict how fast your weight will change.

It adds a warning when the target falls below 1,200 kcal a day for a woman or 1,500 kcal for a man (the lower end of that guideline’s diet ranges), when it falls below 800 kcal (a very-low-calorie diet, which the guideline keeps for medical settings), or when your BMI is under 18.5.

Weight loss is rarely a straight line: water shifts from day to day, and as weight falls, maintenance calories fall too. It’s worth recalculating after a real change in weight. A GP or registered dietitian can help you choose a safe goal.

Limits of the estimate

It is a prediction, not a measurement. Two people with identical numbers can differ by a few hundred calories a day. Only indirect calorimetry measures resting energy directly.
Body composition. The equation uses total weight. It tends to underestimate needs in very muscular people and can overestimate them in people with a lot of body fat. The BMI calculator shows where your weight sits for your height, with the same limits on muscle and fat.
Adults only. It was built on adults aged roughly 19 to 78. Children and teenagers need age-specific references.
Not for illness, pregnancy or breastfeeding. Fever, surgery, injury, some medicines and thyroid conditions all change energy needs, and hospital teams use their own methods. In pregnancy, the due date calculator tells you how far along you are; your midwife can advise on diet.
It works best as a starting point. Watching how your weight actually behaves over a few weeks helps. That tells you more about your own needs than any formula.

Common misconceptions

“I should eat my BMR.” BMR covers basic body functions at rest. Everyday living needs more, which is why the daily figure is always higher.
“The number is exact.” It is an estimate with a margin of error of about 10% for most people, and more for some.
“More exercise means I can always eat more.” Activity factors are broad averages, and fitness trackers often overestimate calories burned.
“Metabolism is fixed.” Energy needs change with age, weight, muscle mass and activity, so it’s worth recalculating when any of these change.

If you want to change your weight, or you have a medical condition that affects eating, a GP or registered dietitian can turn these numbers into a plan that suits you.

Frequently asked questions

How many calories do I need a day?

It depends on your size, age, sex and how active you are. As a broad guide, UK advice (NHS) quotes about 2,000 kcal a day for women and 2,500 kcal for men. Individual needs can be several hundred calories either side, so this calculator gives a personal estimate for maintaining your current weight.

What is the difference between BMR and TDEE?

BMR is what your body burns at rest; TDEE adds everything you do. Basal metabolic rate covers breathing, circulation, temperature and organ function. Total daily energy expenditure adds walking, work and exercise on top. The calculator gets TDEE by multiplying BMR by an activity factor.

How do you calculate BMR?

With a predictive equation. This calculator uses Mifflin-St Jeor: 10 × weight in kg + 6.25 × height in cm − 5 × age, then + 5 for men or − 161 for women. For a 30-year-old woman of 60 kg and 165 cm, the result is 1,320 kcal a day.

How many calories should I eat to lose weight?

Your maintenance figure minus a deficit. The 2013 AHA/ACC/TOS obesity guideline uses a deficit of 500 or 750 kcal a day, the two options under Goal. Real results vary a lot from person to person. The same guideline keeps diets below 800 kcal a day for supervised medical settings, and a GP or registered dietitian can help you set a safe goal.

Which activity level should I choose?

The one that matches a typical week, not your best week. Most people with a desk job who exercise a couple of times a week fit Light. If in doubt, choose the lower level: people tend to overestimate how active they are. You can adjust later, based on how your weight actually changes.

How accurate is the Mifflin-St Jeor equation?

Within about 10% of measured resting energy for most healthy adults, which makes it one of the more reliable equations. For any one person the error can still be larger. This is especially true at the extremes of body size and in very muscular people, so the result is best treated as a starting estimate.

Why is the result rounded?

Because the estimate is not precise enough for single calories to matter. Daily calories to maintain weight, and the target to lose weight, are rounded to the nearest 10 kcal, and the basal metabolic rate to the nearest whole calorie. The working underneath shows the figures before rounding, so you can follow the sum.

Does this work for teenagers, pregnancy or breastfeeding?

No. The equation was developed in adults, and the calculator shows a warning if you enter an age under 18. Growth, pregnancy and breastfeeding all change energy needs in ways this formula does not cover. A doctor, midwife or dietitian can advise you instead.

TDEE and calorie deficit calculator (Mifflin-St Jeor)