Calorie Calculator
Estimate your daily calorie needs using the Mifflin–St Jeor formula. Metric and imperial inputs.
Calorie Calculator Tool
Disclaimer: Calorie estimates are general guides based on the Mifflin–St Jeor formula and are not a substitute for personalised dietary advice. Consult a qualified dietitian or healthcare provider before making significant changes to your diet.
How to Use the Calorie Calculator
Select your unit system
Toggle between Metric (cm / kg) and Imperial (ft + in / lbs) using the buttons at the top of the calculator. Each system has its own height and weight fields, and switching clears the last result.
Enter your age, gender, height and weight
Fill in all four fields accurately. The equation is for adults, so the calculator takes ages 18 to 100 and notes when you are outside the 19 to 78 range it was built on. For height, stand straight without shoes. For weight, use a morning reading after using the bathroom for consistency.
Choose your activity level
Choose the option that best describes a typical week. The multipliers run from 1.2 for sedentary to 1.9 for very hard daily exercise. Most people who work at a desk and exercise little are sedentary or lightly active, and if you are unsure, the lower level is the safer choice.
Get your daily calories instantly
Your estimated maintenance calories appear first, with a lower and a higher target below: maintenance minus 500 kcal and plus 300 kcal. Those two offsets are common rules of thumb rather than prescriptions, and the page explains their limits. If the lower figure falls under 1,200 kcal a day, the result says so, because NICE keeps diets that low for specialist services.
Daily Calories — Your Most Important Health Number
What this calculator estimates
Maintenance calories, or total daily energy expenditure, are the energy you use in a day. The calculator builds the figure in two steps. First it estimates your resting energy expenditure with the Mifflin-St Jeor equation, from weight, height, age and sex. Then it multiplies by an activity factor between 1.2 and 1.9. Eat around that total and your weight should stay roughly steady; eat less and it should fall, slowly.
Where the equation comes from
Mifflin and colleagues (Mifflin et al., Am J Clin Nutr 1990) measured the resting energy expenditure of 498 healthy adults aged 19 to 78 by indirect calorimetry, 247 women and 251 men, about half of them normal weight and half obese. Their equation, simplified, is 10 × weight (kg) + 6.25 × height (cm) − 5 × age + 5 for men, and the same with −161 in place of +5 for women. It explained about 71% of the variation between people (R² = 0.71). In the same study the older Harris-Benedict equations of 1919 overestimated measured resting expenditure by 5%. Adding body-fat distribution did not improve the prediction, but fat-free mass on its own was the best single predictor, which is why two people of the same weight can burn different amounts.
The activity multipliers are a convention, not part of Mifflin's study, and they do not match the physical activity levels the FAO/WHO/UNU expert consultation uses: 1.40–1.69 for a sedentary or light-activity lifestyle, 1.70–1.99 for an active one and 2.00–2.40 for a vigorous one (Human Energy Requirements, 2004, Table 5.3). This calculator's 1.2 is closer to the 1.21 that report gives for people who are totally inactive. The multiplier is the widest source of error in the result. Treat the number as a starting point and adjust it by what your weight actually does over several weeks.
"The bodyweight response to a change of energy intake is slow, with half times of about 1 year."
Hall et al., The Lancet 2011The limits of the 500-calorie rule
The −500 kcal target comes from a familiar rule of thumb: about 7,700 kcal per kilogram, the metric form of 3,500 kcal per pound, so 500 kcal a day would be about 0.45 kg a week. Kevin Hall and colleagues showed why that static arithmetic overpromises. As you lose weight, you need less energy, so a fixed cut produces a shrinking deficit and loss slows; their model puts the half time of the body-weight response at about a year. People with more body fat lose more for the same cut, and take longer to reach a new steady weight. Recalculating as your weight changes keeps the target honest.
When the lower figure is too low
For a small, sedentary or older adult, maintenance minus 500 can be a very small number. A 70-year-old woman of 150 cm and 45 kg who is sedentary comes out at about 1,050 kcal a day to maintain, and about 550 to lose. NICE's 2025 guideline on obesity (NG246, recommendations 1.16.8 and 1.16.9) keeps diets of 800 to 1,200 kcal a day, and diets under 800, for specialist weight-management services with long-term support. When the lower figure crosses either line, the result flags it rather than printing it as a plan. The NHS suggests aiming to lose 0.5 to 1 kg a week.
Body size and ethnicity
A WHO expert consultation (WHO Expert Consultation, The Lancet 2004) found that Asian populations have a different relationship between BMI, body fat and health risk from European ones: a substantial share of Asian people are at high risk of type 2 diabetes and cardiovascular disease at BMIs below 25. It kept the international cut-offs but proposed additional public-health action points at 23, 27.5, 32.5 and 37.5. That is a finding about risk at a given BMI. It does not change the calorie estimate here, which depends on weight, height, age and sex, but it is a reason not to judge a healthy weight by BMI alone.
What Mifflin measured, and what the 500-calorie rule leaves out
The Mifflin-St Jeor equation was derived from 498 healthy adults aged 19 to 78, measured by indirect calorimetry.
The group was 247 women and 251 men, with 264 of normal weight and 234 obese.
The simplified equation for men is 10 × kg + 6.25 × cm − 5 × age + 5; for women the constant is −161.
The equation explained about 71% of the variation in resting energy expenditure between people.
In Mifflin's study, the 1919 Harris-Benedict equations overestimated measured resting expenditure by 5%.
Fat-free mass was the best single predictor of resting expenditure in the same study.
This calculator's activity multipliers run from 1.2 (sedentary) to 1.9 (very hard daily exercise). They are a convention, not part of Mifflin's study.
Hall and colleagues found body weight responds to a change in intake slowly, with a half time of about a year.
People with more body fat lose more for the same cut in intake, Hall's model found, and take longer to settle.
A WHO consultation found many Asian people are at high risk of diabetes and heart disease at BMIs below 25.
Frequently Asked Questions
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There is no single number. This calculator estimates your maintenance calories from your age, sex, height, weight and activity level. It also shows maintenance minus 500 kcal and plus 300 kcal as rough loss and gain targets. Use the result as a starting point, then adjust it by what your weight does over several weeks.
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Maintenance calories (also called TDEE — Total Daily Energy Expenditure) is the number of calories your body burns in a typical day, accounting for both your resting metabolism and your physical activity. Eating at exactly this number keeps your weight stable over time.
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For most healthy adults a moderate cut like this is a common starting point, but it does not keep producing 0.45 kg a week. Hall and colleagues showed that as weight falls, energy needs fall too, so a fixed cut produces a shrinking deficit and weight loss slows. For a small or older person the lower figure can fall under 1,200 kcal a day, a level NICE keeps for specialist services, and the result flags it when it does. If you are pregnant, have a medical condition or take medication, talk to a doctor or registered dietitian before cutting calories.
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Any food diary works if you use it consistently. Enter the target from this calculator as your goal, log what you eat, and compare the trend in your weight with what you expected. If your weight moves faster or slower than planned for several weeks, adjust the target rather than the diary.
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The Mifflin-St Jeor equation was derived from 498 adults in the United States, and we have not found a validation study in Southeast Asian adults that we could read and cite. What is well documented is that Asian populations carry more health risk at a given BMI: a WHO expert consultation found a substantial share at high risk below a BMI of 25. For an individual figure, a measured test of resting energy expenditure is more reliable than any equation.
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This Calorie Calculator gives you a single fast result: your daily maintenance calories plus simple loss and gain targets. The TDEE & Calorie Calculator goes deeper — it uses the same Mifflin-St Jeor equation and the same activity factors, so the two give the same maintenance figure, and it adds a protein, carbohydrate and fat split for each goal. Use this tool for a quick number; use the TDEE Calculator for the macro split.
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In Mifflin's original study, the equation explained about 71% of the variation in resting energy expenditure between people, so individuals can sit well above or below it. The activity multiplier adds more uncertainty, because it depends on your own estimate of how active you are. The best check is your weight over several weeks at the calculated intake.
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Choose the level that matches a typical week, not your best one. A desk job with little exercise is sedentary (×1.2); one to three sessions of structured exercise a week is lightly active (×1.375). If you are unsure, pick the lower level, and move up only if you lose weight when you meant to maintain it.
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Whenever your weight changes by several kilograms or your activity changes. The Mifflin-St Jeor equation lowers resting expenditure by 10 kcal for each kilogram lost, so after losing 10 kg your estimate falls by about 100 kcal before the activity multiplier, and about 120 to 190 kcal after it. That is one reason a deficit that worked at the start stops working.
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Method & sources
How it computes
EnergyNeedsKernel (shared with /tdee-calculator/): Mifflin-St Jeor 1990 resting energy (10 × kg + 6.25 × cm − 5 × age + 5, or −161 for women) × an activity factor of 1.2-1.9, a calculator convention rather than the FAO/WHO/UNU activity levels. −500 and +300 kcal are shown as rules of thumb; a −500 figure under NICE NG246's 1,200 or 800 kcal/day line is flagged, and ages outside Mifflin's 19-78 sample are noted.
What this tool implements
- Mifflin 1990: derived from 498 healthy adults aged 19-78 by indirect calorimetry; R² = 0.71; Harris-Benedict overestimated measured REE by 5%. The activity factors are a convention and the page says so.
- Removed as unsourced: an HPB '1,800-2,200 kcal' recommendation, an NPHS 11.6% obesity figure, a '65% of adults below 150 minutes' survey, Malaysian and Indonesian survey figures, hawker-dish calorie counts, a '±10%' accuracy claim and a pull-quote calling 500 kcal 'the evidence-based sweet spot'.
- Hall 2011: body weight responds to an intake change with a half time of about a year, so the 0.45 kg/week of the −500 target is an early-weeks figure at best. WHO 2004 on Asian BMI is cited as a risk finding, not as a calorie adjustment.
- FAO/WHO/UNU 2004, Table 5.3: sedentary or light activity 1.40-1.69, active 1.70-1.99, vigorous 2.00-2.40, and 1.21 for people who are totally inactive; the page sets the calculator's 1.2-1.9 against these rather than presenting them as measured.
- NICE NG246 (2025) 1.16.8-1.16.9: diets of 800-1,200 kcal/day, and under 800, only within specialist services. When the −500 figure crosses either line the result says so; the page works the case of a sedentary 70-year-old woman of 150 cm and 45 kg (about 1,050 to maintain, 550 to lose). NHS guidance of 0.5-1 kg a week is quoted for pace.
- Inputs: adults 18-100 in whole years (ages outside Mifflin's 19-78 noted); 1 lb = 0.45359237 kg and 1 in = 2.54 cm exactly; feet 3-8 as a whole number, inches 0-11, the result inside 100-250 cm; 67-661 lb (the 66 lb floor was 29.94 kg, under the 30 kg one).
Sources
- Mifflin MD, St Jeor ST, Hill LA, Scott BJ, Daugherty SA, Koh YO. A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr 1990;51(2):241-247. https://doi.org/10.1093/ajcn/51.2.241
- Hall KD, Sacks G, Chandramohan D, Chow CC, Wang YC, Gortmaker SL, Swinburn BA. Quantification of the effect of energy imbalance on bodyweight. Lancet 2011;378(9793):826-837. https://doi.org/10.1016/S0140-6736(11)60812-X
- WHO Expert Consultation. Appropriate body-mass index for Asian populations and its implications for policy and intervention strategies. Lancet 2004;363(9403):157-163. https://doi.org/10.1016/S0140-6736(03)15268-3
- FAO/WHO/UNU. Human Energy Requirements: Report of a Joint FAO/WHO/UNU Expert Consultation, Rome, 17-24 October 2001. FAO Food and Nutrition Technical Report Series 1; 2004. Table 5.3: https://www.fao.org/4/y5686e/y5686e07.htm
- National Institute for Health and Care Excellence. Overweight and obesity management (NG246), 2025, recommendations 1.16.8-1.16.9. https://www.nice.org.uk/guidance/ng246/chapter/Physical-activity-…
- Hall KD. What is the required energy deficit per unit weight loss? Int J Obes 2008;32(3):573-576 (3,500 kcal per pound, 32.2 MJ per kg). https://pmc.ncbi.nlm.nih.gov/articles/PMC2376744/
- NHS. Tips to help you lose weight ("aim to lose 1 to 2lbs, or 0.5 to 1kg, a week"). https://www.nhs.uk/live-well/healthy-weight/managing-your-weight/…
What can make this go out of date
- None at runtime — the equation, the activity convention and the NICE thresholds are fixed publications.
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