Your TDEE (total daily energy expenditure) is the number of calories you burn in a day, including exercise. To estimate it, work out your basal metabolic rate (BMR) with the Mifflin-St Jeor equation, then multiply by an activity factor between 1.2 and 1.9. Eating around your TDEE keeps your weight steady; eating less or more moves it down or up.
What BMR and TDEE mean
BMR is the energy your body uses at rest to breathe, circulate blood and keep warm. TDEE adds everything else: walking, work, exercise and digesting food. Most people’s TDEE is well above their BMR, which is why you cannot judge your needs from BMR alone.
The Mifflin-St Jeor equation
The calculator uses this widely used equation for adults:
- Men: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age + 5
- Women: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age − 161
Then TDEE = BMR × activity multiplier.
| Activity level | Multiplier |
|---|---|
| Little or no exercise | 1.2 |
| Light exercise, 1 to 3 days a week | 1.375 |
| Moderate exercise, 3 to 5 days a week | 1.55 |
| Hard exercise, 6 to 7 days a week | 1.725 |
| Very hard exercise or a physical job | 1.9 |
Worked example
Take a 35-year-old woman, 165 cm and 65 kg, who exercises lightly one to three days a week.
- BMR: 10 × 65 + 6.25 × 165 − 5 × 35 − 161 = 1,345 kcal
- TDEE: 1,345 × 1.375 = about 1,850 kcal a day
From that maintenance figure, the Calorie and TDEE tool suggests roughly 1,575 kcal to lose 0.25 kg a week or 1,300 kcal to lose 0.5 kg a week. It does not show targets below 1,200 kcal.
Turning TDEE into a goal
A moderate deficit is generally easier to stick to than a steep one. To lose weight, eat below your TDEE; to gain, eat above it. The weekly figures above are estimates, since the equation predicts averages and individuals differ.
Treat the result as a starting point. Track your weight and energy over two to four weeks, then adjust by 100 to 200 kcal if progress is not what you expected. Your weight is also only one measure, so it can help to look at BMI explained: what it tells you and what it doesn't and Body fat percentage: how it's measured and what's typical alongside it.
Where the calories come from
Calories come from protein (4 kcal per gram), carbohydrate (4 kcal per gram), fat (9 kcal per gram) and alcohol (7 kcal per gram). Once you have a daily target, you can split it into those nutrients. Macros for beginners: protein, carbs and fat explains how, and the Calories and macros tool converts a calorie target into grams.
Why your real needs may differ
- Muscle burns more than fat at rest, so two people of equal weight can differ.
- Activity level is the biggest guess. Many people overestimate it, so pick the lower level if unsure.
- Age, sleep, stress and some medical conditions or medicines affect energy needs.
- The equation is for adults and does not apply to pregnancy, breastfeeding or children.
Note: This is general information, not medical advice. Speak to a GP or dietitian before cutting calories sharply, or if you have a health condition or a history of disordered eating.
Common questions about eating at a deficit or surplus
Smaller changes tend to be easier to keep up. Cutting 250 to 500 kcal below TDEE is the kind of gap the calculator shows, and it usually feels more manageable than a crash diet. Do not eat below the amounts your GP or dietitian recommends, and avoid very low targets without supervision.
For gaining weight, a modest surplus plus regular strength training gives your body a reason to build muscle rather than only add fat. Either way, re-run the calculation when your weight changes by a few kilograms, because your maintenance figure moves with your body size.
Try the calculator
Use Calorie and TDEE to estimate your BMR and daily calories for losing, keeping or gaining weight, then Calories and macros to turn a target into grams of protein, carbohydrate and fat. Both give estimates.
Open the free Calorie and TDEE
Worked example 2: a 40-year-old man
The first example covered a woman. Here is a second one, run through the TDEE calculator’s engine: a man aged 40, 180 cm tall and 85 kg.
- BMR: 10 × 85 + 6.25 × 180 − 5 × 40 + 5 = 850 + 1,125 − 200 + 5 = 1,780 kcal
- If he exercises lightly (1.375): TDEE = about 2,448 kcal
- If he exercises moderately three to five days a week (1.55): TDEE = about 2,759 kcal
| Goal | Light activity | Moderate activity |
|---|---|---|
| Maintain | 2,448 kcal | 2,759 kcal |
| Lose 0.25 kg a week | 2,173 kcal | 2,484 kcal |
| Lose 0.5 kg a week | 1,898 kcal | 2,209 kcal |
| Gain 0.25 kg a week | 2,723 kcal | 3,034 kcal |
The BMR does not change, but choosing the next activity level up adds over 300 kcal a day. That is why the activity choice matters more than anything else in the sum. A person who is honest about a desk job and two gym sessions will usually fit the lighter row better than the heavier one. Each 0.25 kg a week corresponds to roughly 275 kcal a day below or above maintenance, which is a common rule of thumb rather than an exact law.
Step-by-step: how to work it out by hand
- Convert your weight to kilograms and height to centimetres (1 inch is 2.54 cm; 1 stone is 6.35 kg; 1 lb is 0.4536 kg).
- Multiply weight by 10, height by 6.25, and age by 5.
- Add the first two, subtract the age figure, then add 5 (men) or subtract 161 (women). That is your BMR.
- Multiply by the activity factor that best matches a typical week.
- For a goal, subtract about 275 kcal a day per 0.25 kg a week you want to lose, or add the same to gain.
- Check the result is not below the lowest level your GP or dietitian would advise.
Why the scale does not move in a straight line
Weight can change by a kilogram or more from one day to the next because of fluid, salt, food still in the gut and, for some women, the menstrual cycle. These swings hide the slower change in body fat. Weigh yourself under the same conditions, ideally the same time of day, and look at the average across a week rather than a single reading. If the weekly average has not moved after two to four weeks, adjust your intake by 100 to 200 kcal a day or add some walking, then give it another few weeks. The guide to BMI explained: what it tells you and what it doesn't explains what weight alone can and cannot say about health.
Calories, protein and keeping muscle
When you eat less, a decent protein intake and regular strength training help you keep muscle while you lose fat. The best split for you depends on your size, goal and any health conditions, so use Macros for beginners: protein, carbs and fat to turn a calorie target into grams of each nutrient, and ask a dietitian if you have specific medical needs. Alcohol counts too, at 7 kcal per gram, and drinks can add up quickly without feeling filling.
Common mistakes
- Overestimating activity. A step count or a workout does not make you “very active” for the whole week.
- Ignoring weekends. Five careful days and two relaxed ones can erase a weekly deficit.
- Cutting too hard. A steep deficit is hard to keep up and can leave you tired and hungry.
- Trusting wearable burn figures. Devices estimate calorie burn with their own formulas and can differ a lot from each other.
- Not recalculating. After a loss of a few kilograms, your maintenance figure falls, so work it out again.
Glossary
- BMR: calories burned at complete rest.
- TDEE: total daily energy expenditure, BMR plus activity and digestion.
- Deficit / surplus: eating below or above TDEE.
- Maintenance calories: the intake at which your weight stays stable.
- Kilocalorie (kcal): what people usually mean by a “calorie” on food labels.
Planning a week, not a day
Your weight responds to what you eat over weeks, so you do not need to hit an exact number each day. Some people split the target across the week: for example, a daily target of 1,900 kcal is 13,300 kcal for the week, which can be spread across seven days with a little flexibility for a meal out. What matters is the weekly average. If you find strict daily numbers stressful, a simpler approach is to choose a typical day of meals that comes close to your target and repeat it with small swaps.
Reading food labels
UK labels show energy in kilojoules (kJ) and kilocalories (kcal). The kcal figure is the one to compare with your target. Labels may give values per 100 g and per portion, and the portion in the pack may not match what you actually eat, so check which column you are reading. Measuring a portion on kitchen scales for a few days is a good way to learn what the amounts look like. Oils, spreads, dressings and drinks are easy to underestimate, because small amounts carry a lot of energy at 9 kcal per gram of fat.
When to speak to a professional
Talk to a GP, registered dietitian or other health professional before starting a calorie target if you are under 18, pregnant or breastfeeding, have diabetes or another long-term condition, take regular medicines, or have ever had an eating disorder. They can set targets that fit your health, which a general equation cannot do. If counting calories makes you anxious or controlling, that is a good reason to stop and seek support.
Frequently asked questions
How many calories should I eat a day?
It depends on your age, sex, size and activity. The equation above gives an estimate of what keeps your weight steady.
Is BMR the same as TDEE?
No. BMR is your resting energy use. TDEE is BMR plus activity, so it is always higher.
Which activity level should I choose?
Choose honestly based on your typical week, including your job. If you are between two levels, pick the lower one and adjust after tracking.
How accurate is the Mifflin-St Jeor equation?
It is a good estimate for many adults, but it is still an average. Use it as a starting point and adjust to your real results.
How many calories should I cut to lose weight safely?
A modest deficit, such as the 250 to 500 kcal below maintenance our calculator shows, is easier to sustain than a drastic cut. Speak to a GP or dietitian before going lower, and especially if you have a medical condition.
Does TDEE change as I lose weight?
Yes. A smaller body needs less energy, so recalculate after each few kilograms of change.
Can I use TDEE if I am pregnant or breastfeeding?
No. The equation is for adults who are not pregnant or breastfeeding, because energy needs differ. Ask your midwife, GP or health visitor.
Should I eat back the calories I burn exercising?
It depends on how you chose your activity level. If your multiplier already reflects your usual exercise, do not add it again. Otherwise, treat tracker estimates cautiously.