Calorie
calculator.
Estimate how many calories a day keep your weight steady (your TDEE), using the National Academies’ 2023 equations fitted to measured energy use or your BMR times an activity level. Then see the daily target for losing or gaining a chosen amount each week.
About 2,898 kcal a day keeps your weight steady (NASEM 2023 equation, low active).
- Maintenance (TDEE)
- 2,898 kcal/day
- Target in kilojoules
- 12,125 kJ/day
- Typical error of the equation (RMSE)
- ±339 kcal/day
- BMR (Mifflin-St Jeor)
- 1,758 kcal/day
- Equivalent PAL (TDEE ÷ BMR)
- 1.65
- Height and weight used
- 177.8 cm, 81.6 kg
TEE = 581.47 − 10.83 × 35 + 8.30 × 177.8 + 14.94 × 81.6466 = 2,897.96 kcal/dayDaily energy,
estimated honestly.
- NASEM 2023 (default): TEE = a − b × age + c × height (cm) + d × weight (kg), with separate coefficients for men and women and for four activity levels (inactive, low active, active, very active). Their typical error is ±339 kcal a day for men and ±246 for women.
- BMR × PAL: a resting estimate (Mifflin-St Jeor, revised Harris-Benedict or Katch-McArdle) times a physical activity level from 1.0 to 2.5. FAO/WHO/UNU’s examples are 1.53 (sedentary or light), 1.76 (moderately active) and 2.25 (vigorous). The matching NASEM equation is shown as a cross-check.
- Weight-change target: maintenance ± weekly change × 3,500 kcal per lb ÷ 7. One pound a week is 500 kcal a day; 0.5 kg a week is 551 kcal a day.
- US inputs are converted exactly (1 in = 2.54 cm, 1 lb = 0.45359237 kg); results are shown to the nearest kcal and 1 kcal = 4.184 kJ.
- For adults aged 19 to 100 who are not pregnant or breastfeeding. Targets under 1,200 kcal (women) or 1,500 kcal (men) are flagged, and under 800 kcal is marked as a very-low-calorie diet.
How do you calculate how many calories you need a day?
The National Academies’ 2023 energy report gives one equation for each sex and activity level, fitted to daily energy use measured with doubly labeled water. For a low active man the equation is 581.47 − 10.83 × age + 8.30 × height (cm) + 14.94 × weight (kg). A 35-year-old man who is 5 ft 10 in (177.8 cm) and 180 lb (81.65 kg) needs 581.47 − 379.05 + 1,475.74 + 1,219.80 = 2,898 kcal a day to stay at the same weight. The same man would need 2,681 kcal if inactive and 3,439 if very active.
Men, low active: TEE = 581.47 − 10.83A + 8.30H + 14.94W
Women, low active: TEE = 575.77 − 7.01A + 6.60H + 12.14W
A = years, H = cm, W = kgWhat is TDEE and how is it calculated from BMR?
Total daily energy expenditure (TDEE) is everything you burn in a day: resting metabolism, digestion and movement. The classic shortcut is TDEE = BMR × PAL, where the physical activity level PAL is daily energy divided by BMR. A 30-year-old woman who is 165 cm and 68 kg has a Mifflin-St Jeor BMR of 1,400.25 kcal; at PAL 1.53, the FAO/WHO/UNU example for a sedentary or light lifestyle, her TDEE is 1,400.25 × 1.53 = 2,142 kcal. The NASEM equation for the matching low active level gives 2,280 kcal, and the calculator shows both so you can see how much the method matters.
TDEE = BMR × PAL
PAL = total daily energy ÷ BMRWhich activity level should I choose?
NASEM defines inactive as roughly basal metabolism plus daily living (PAL 1.00 to 1.53 for adults), low active as more walking (1.53 to 1.68), active as more walking plus occupational or recreational activity (1.68 to 1.85) and very active as vigorous exertion at work or in sport (1.85 to 2.50). FAO/WHO/UNU note that PAL values above 2.40 are difficult to maintain for long. If you are unsure, start one level lower and check your weight trend after a few weeks; for the 35-year-old man above, each step up adds 186 to 355 kcal a day.
How many calories should I eat to lose weight?
Subtract a daily deficit from maintenance. The common rule counts 3,500 kcal per pound, so losing 1 lb a week needs 3,500 ÷ 7 = 500 kcal a day less: the 35-year-old man would aim for 2,898 − 500 = 2,398 kcal a day. The AHA/ACC/TOS obesity guideline’s usual prescriptions are a 500 or 750 kcal daily deficit, or 1,200 to 1,500 kcal a day for women and 1,500 to 1,800 for men, adjusted for body weight. It says diets under 800 kcal a day should be used only with medical supervision.
target = maintenance − weekly loss (lb) × 3,500 ÷ 7
1 lb a week ≈ 500 kcal a day; 0.5 kg a week ≈ 551 kcal a dayIs 3,500 calories really one pound?
As a long-run average it is only a rule of thumb. Kevin Hall of the NIH showed that the energy in each pound lost depends on body fat: the rule roughly fits people with more than 30 kg of body fat but overstates the deficit needed per pound for leaner people. Your energy needs also fall as you lose weight, so a fixed 500 kcal deficit produces slower loss over time. Use the target as a starting point and adjust it from your actual trend.
How many calories do I need to gain weight?
Add a daily surplus to maintenance in the same way. A 22-year-old man who is 6 ft (182.88 cm), weighs 160 lb and is very active needs about 3,486 kcal a day to maintain; to gain 0.5 lb a week he would aim for 3,486 + 250 = 3,736 kcal a day. How much of the gain is muscle depends on training and protein, which this calculator does not model.
Worked examples.
Maintenance for a low active man
Male, 35 years, 5 ft 10 in, 180 lb, NASEM equation, low active.
2,898 kcal/day to maintain (±339 kcal typical error).
Load this exampleLosing 1 lb a week
The same man, aiming to lose 1 lb a week.
2,398 kcal/day: 500 kcal below his 2,898 kcal maintenance.
Load this exampleMetric: losing 0.5 kg a week
Female, 30 years, 165 cm, 68 kg, NASEM equation, low active, lose 0.5 kg a week.
1,729 kcal/day: 551 kcal below her 2,280 kcal maintenance.
Load this exampleBMR × activity level
The same woman, Mifflin-St Jeor BMR × PAL 1.53, maintain.
2,142 kcal/day (NASEM low active cross-check: 2,280).
Load this exampleA fast rate is flagged
Female, 45 years, 5 ft 4 in, 140 lb, inactive, lose 2 lb a week.
943 kcal/day, which is under 1,200 kcal and flagged; a slower rate is suggested.
Load this exampleLean-mass BMR for an athlete
Male, 50 years, 183 cm, 95 kg, 22% body fat, Katch-McArdle BMR × PAL 1.76, maintain.
3,468 kcal/day (NASEM active cross-check: 3,168).
Load this exampleWhat this calculator
does not do.
- Every equation predicts an average for people like you. The NASEM equations’ typical error is ±339 kcal a day for men and ±246 for women, and BMR × PAL depends heavily on the activity level you pick.
- The weight-change target uses the static 3,500 kcal per pound rule. Real loss usually slows as weight falls, and the energy per pound varies with body fat.
- For adults only. It does not cover pregnancy, breastfeeding, children, athletes in heavy training blocks, eating disorders or medical conditions, where needs differ.
- An informational estimate, not medical or dietary advice. Talk to a clinician or registered dietitian before a large deficit or a very low intake.
Common questions.
How many calories should I eat a day?
It depends on your size, age, sex and activity. For a 35-year-old, 5 ft 10 in, 180 lb man who is low active, the NASEM equation gives about 2,898 kcal a day to maintain. Enter your own details for your estimate.
What is the difference between BMR and TDEE?
BMR is the energy you use at complete rest. TDEE adds digestion and all movement, and is usually about 1.4 to 2.0 times BMR. The BMR calculator shows BMR alone.
Where do the activity multipliers come from?
Here they are physical activity levels (daily energy ÷ BMR) from FAO/WHO/UNU’s human energy requirements report and the NASEM 2023 activity ranges. The popular 1.2 to 1.9 multipliers on many sites are not tied to a source we could verify, so we do not use them.
How long will it take to lose 10 pounds?
At 500 kcal a day below maintenance the rule of thumb says about 1 lb a week, so roughly 10 weeks, but real loss usually slows over time.
Why does the calculator flag my target?
Targets under 1,200 kcal a day for women or 1,500 for men are below the usual guideline weight-loss prescriptions, and under 800 kcal is a very-low-calorie diet, which the AHA/ACC/TOS guideline reserves for medical supervision.
- National Academies of Sciences, Engineering, and Medicine. Dietary Reference Intakes for Energy (2023), Summary, Table S-1 — adult TEE equations for four activity levels; RMSE 339 kcal/day (men) and 246 (women)
- NASEM. Dietary Reference Intakes for Energy (2023), chapter 5: development of prediction equations — adult PAL ranges: inactive 1.00–1.53, low active 1.53–1.68, active 1.68–1.85, very active 1.85–2.50
- FAO/WHO/UNU. Human energy requirements, 2001 consultation, chapter 5: energy requirements of adults — PAL = TEE ÷ BMR; examples at 1.53, 1.76 and 2.25; PAL above 2.40 difficult to maintain
- Mifflin MD, St Jeor ST et al. A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr 1990 (PubMed abstract) — the default BMR equation for BMR × PAL
- Jensen MD et al. 2013 AHA/ACC/TOS Guideline for the Management of Overweight and Obesity in Adults (PMC) — 1,200–1,500 kcal/day (women) and 1,500–1,800 (men), or a 500 or 750 kcal/day deficit; very-low-calorie diets (<800 kcal/day) only under medical supervision
- Hall KD. What is the required energy deficit per unit weight loss? Int J Obes 2008;32:573-6 (PMC) — the 3,500 kcal per pound rule, when it fits and when it overestimates
Maintenance comes from the NASEM 2023 adult equations or from a BMR equation times your PAL, using height in centimetres and weight in kilograms (US inputs converted exactly). The target adds or subtracts the weekly change at 3,500 kcal per pound. Our tests check six worked cases against a separate 40-digit Python Decimal script with the coefficients typed from the report. They confirm that US and metric entries of the same body agree, that the equations rise with weight and height and fall with age, that each activity level gives more than the one below for typical adults, that BMR × PAL matches the BMR calculator, and that the target always differs from maintenance by exactly the stated deficit.
Built and reviewed by CalculatorLab against the sources above; every worked example on this page is re-checked by our automated test suite before each release. How we build and check calculators. Found a problem? Tell us.