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What is TDEE?
TDEE, or total daily energy expenditure, is the number of calories you burn in a day: your resting rate (BMR) plus everything you do on top of it, from walking and exercise to digesting food. Eat about your TDEE and your weight tends to stay steady. Eat less and you're in a calorie deficit; eat more and you're in a surplus. The NHS puts the average at around 2,500 kcal a day for a man and 2,000 for a woman, but your own number depends on your size, age and how active you are.
How to calculate TDEE and a calorie deficit
The calculator estimates your BMR with the Mifflin-St Jeor equation, multiplies it by an activity factor from 1.2 (mostly sitting) to 1.9 (very active), then takes off your chosen deficit.
| Step | Formula |
|---|---|
| BMR (men) | 10 × weight (kg) + 6.25 × height (cm) − 5 × age + 5 |
| BMR (women) | 10 × weight (kg) + 6.25 × height (cm) − 5 × age − 161 |
| TDEE (maintenance calories) | BMR × activity factor (1.2 to 1.9) |
| Calorie deficit target | TDEE − 250 or − 500 kcal, never below 1,200 (women) or 1,500 (men) |
Worked example: a 40-year-old woman, 165 cm (5′5″) and 65 kg (10 st 3 lb), lightly active. BMR = 10 × 65 + 6.25 × 165 − 5 × 40 − 161 = 1,320 kcal. TDEE = 1,320 × 1.375 ≈ 1,815 kcal a day. A 500 kcal deficit gives a target of about 1,315 kcal a day.
What calorie deficit should I be in?
For most adults, 250 to 500 kcal a day below your TDEE is a sensible place to start. The NHS suggests aiming to lose 0.5 to 1 kg (1 to 2 lb) a week; a smaller deficit is slower but easier to keep up. We don't show targets below 1,200 kcal a day for women or 1,500 for men, because the NHS notes that very low calorie diets aren't suitable or safe for everyone.
| Daily deficit | Loss per week at first | Loss per month at first |
|---|---|---|
| 250 kcal | about 0.25 kg (½ lb) | about 1 kg (2 lb) |
| 500 kcal | about 0.5 kg (1 lb) | about 2 kg (4 lb) |
How many calories is a pound of fat?
The old rule of thumb is about 3,500 kcal per pound (7,700 per kilogram), so a 500 kcal daily deficit loses about 1 lb a week. It works for the first few weeks, then overestimates: as you get lighter you burn less, so loss slows. Researchers at the US National Institutes of Health found that the body's response to a change in eating takes about a year to get halfway to its new steady weight (Hall and colleagues, The Lancet, 2011). Their free Body Weight Planner models this. The timeline in our calculator uses the simple rule, so treat it as the shortest likely time, not a promise.
Calorie deficit for women and men
For the same age, height and weight, the equation gives women 166 kcal a day less than men, because women carry less muscle on average. That's why the calculator asks which sex to use. A woman's lower starting point also means a 500 kcal deficit is a bigger share of her day, which is why our floor is 1,200 kcal for women and 1,500 for men. If neither option fits you, try both and treat the answer as a range.
Is a TDEE calculator accurate?
It's a good starting estimate, not a measurement. A systematic review of the common equations found Mifflin-St Jeor, the one we use, the most reliable: it predicted resting energy use within 10% of the measured value in more people than the alternatives (Frankenfield and colleagues, 2005). Some people are still further out, and the activity level adds guesswork of its own. Weigh yourself weekly for a month and adjust by 100 to 200 kcal if your trend doesn't match.
Teens, pregnancy and when not to count calories
- Under 18: the equation is for adults, and growing bodies need energy to grow. We don't show deficits for teens; a doctor or school nurse can check growth and weight properly.
- Pregnant or breastfeeding: your needs change and the equation doesn't account for that. The NHS says there's no need to "eat for 2", but don't aim for a deficit without your midwife or doctor.
- An eating disorder, now or in the past: counting calories can make things worse. Talk to your clinician rather than using a target.
- Diabetes medicines, kidney disease or other conditions: plan changes with your clinician, as some medicines need adjusting when you eat less.
What to do next
- Track for a month. Weigh yourself weekly at the same time of day and adjust by 100 to 200 kcal if the trend doesn't match your goal.
- Check your starting point with the BMI calculator and the waist-to-height ratio.
- Get free support. Your GP, family doctor or primary-care clinician can refer you to weight management services; see free care routes.
- Thinking about weight-loss medicine? The medical weight-loss check shows who qualifies and the covered routes first.
Common questions
What calorie deficit should I be in?
For most adults, 250 to 500 calories a day below your TDEE is a sensible start, which works out at roughly 0.25 to 0.5 kg (half a pound to a pound) a week at first. Smaller deficits are easier to keep up. We don't suggest going below 1,200 kcal a day for women or 1,500 for men without clinical support.
What's the difference between BMR and TDEE?
BMR, or basal metabolic rate, is the energy your body uses at complete rest just to keep you alive. TDEE, or total daily energy expenditure, adds the energy you use moving, exercising and digesting food. TDEE is the number to compare with what you eat if you want to maintain, lose or gain weight.
How many calories do I need to cut to lose 1 pound?
The rule of thumb is about 3,500 calories per pound, or 500 a day for a week. It holds for the first few weeks, but as you lose weight you burn less, so progress slows. Research from the US National Institutes of Health shows the full effect takes years, so expect slower loss than the rule predicts.
Is a TDEE calculator accurate?
It's a reasonable estimate, not a measurement. The Mifflin-St Jeor equation we use was the most reliable of the common formulas in a systematic review, predicting resting energy use within 10% for more people than the alternatives. Your real needs can still differ, so track your weight for a month and adjust.
Is 1,200 calories a day safe?
It can be too little for many adults, particularly men and people who are active. We don't suggest targets below 1,200 kcal a day for women or 1,500 for men without clinical support. The NHS notes that very low calorie diets aren't suitable or safe for everyone, and a dietitian can help if you need one.
Can I use a TDEE calculator if I'm pregnant?
Not to set a deficit. The equation doesn't account for pregnancy or breastfeeding, and the NHS says there's no need to eat for two. Your needs change as pregnancy goes on, so talk to your midwife, doctor or a dietitian before trying to lose weight or changing how much you eat.
Does this calculator work if I take a weight-loss medicine?
It still estimates your energy needs, but medicines such as semaglutide and tirzepatide reduce appetite, so many people eat well below these numbers without trying. Focus on getting enough protein, fluids and nutrients, and follow the eating advice from your prescriber rather than chasing a calorie target.
Sources
- Mifflin MD, St Jeor ST, et al. A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr, 1990;51(2):241–7.
- Frankenfield D, Roth-Yousey L, Compher C. Comparison of predictive equations for resting metabolic rate in healthy nonobese and obese adults: a systematic review. J Am Diet Assoc, 2005;105(5):775–89.
- Hall KD, Sacks G, Chandramohan D, et al. Quantification of the effect of energy imbalance on bodyweight. The Lancet, 2011;378(9793):826–37.
- NIDDK (US National Institutes of Health). Body Weight Planner.
- NHS. Understanding calories.
- NHS. Overweight and obesity in adults — treatment.
- NHS. Have a healthy diet in pregnancy.
General information, not medical advice — see our medical disclaimer. These results are estimates and can't diagnose anything. In an emergency, call 911 (US, Canada) or 999 (UK).