Calorie calculator
How many calories you burn in a day, at rest and with your activity: roughly what keeps your weight steady.
Calories you burn a day
2,084 calories
moderately active, at 143 lb
- 1,345 at rest
- Activity × 1.55
At 35, 5 ft 5 in and 143 lb, a moderately active woman burns about 2,084 calories a day: roughly what you can eat to keep your weight where it is.
About 1,345 of them keep your body running at rest; moving around and exercise add the other 739.
I’m not a doctor or a dietitian. This is an estimate, for information only. For decisions about your health, check with a professional.
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Your calories at each activity level
| Activity level | Multiplier | Calories a day |
|---|---|---|
| Sedentary | × 1.2 | 1,613 |
| Lightly active | × 1.375 | 1,849 |
| Moderately active (you) | × 1.55 | 2,084 |
| Very active | × 1.725 | 2,319 |
| Extra active | × 1.9 | 2,555 |
In short: The NHS uses about 2,000 calories a day for women and 2,500 for men as a guide. Your own number is your resting burn multiplied by an activity factor from 1.2 to 1.9.
How it works
- First, your resting burn: the calories your body uses in a day at complete rest. The calculator uses the Mifflin-St Jeor equation (1990): 10 × weight in kilograms + 6.25 × height in centimeters − 5 × age, then + 5 for men or − 161 for women. Pounds, feet and inches are converted first.
- Then it multiplies by an activity factor: 1.2 if you’re sedentary, 1.375 lightly active, 1.55 moderately active, 1.725 very active, 1.9 extra active. The result is what you burn on a typical day, which is roughly what you can eat to keep your weight steady.
- These are food calories, the ones on nutrition labels (kilocalories, or kcal).
Worked example
A 35-year-old woman, 5 ft 5 in (165.1 cm) and 143 lb (64.86 kg): 10 × 64.864 + 6.25 × 165.1 − 5 × 35 − 161 = 1,344.5 calories at rest. Moderately active, × 1.55 = 2,084 calories a day. If she were sedentary, she would burn about 1,613; if very active, about 2,319.
Sources
- Mifflin and others (1990), American Journal of Clinical Nutrition: the equation (PubMed)
- Frankenfield and others (2005), Journal of the American Dietetic Association: how accurate the equations are (PubMed)
- FAO, WHO and UNU: Human energy requirements, energy needs as resting burn × activity level
- USDA and HHS: Dietary Guidelines for Americans, 2025–2030 (PDF)
- FDA nutrition labeling rules, 21 CFR 101.9: the 2,000-calorie reference on labels
- NHS: Understanding calories (UK)
Text checked on September 30, 2026
Good to know
- It’s an estimate. In a 2005 review, this equation came within 10% of the measured value for more people than any other common equation, but for some people it misses by more.
- The activity multipliers are a convention: nearly every calculator uses these five, but nobody measured them for you. If your weight keeps drifting while you eat this amount, your real number is a bit different.
- Older adults and some ethnic groups were underrepresented in the studies behind these equations, so the estimate is less certain for them.
- It isn’t meant for pregnancy, breastfeeding, teens or athletes in heavy training: their needs are different, and a doctor or registered dietitian can work them out.
Frequently asked questions
How many calories do I need a day?
It depends on your age, sex, height, weight and how active you are, which is what this calculator works out. As a rough guide, the NHS says an average man needs about 2,500 calories a day and an average woman about 2,000. US nutrition labels use 2,000 a day for general advice.
What’s the difference between BMR and TDEE?
BMR (basal metabolic rate) is what you burn at complete rest; this calculator gives your resting burn, which is very close to it. TDEE (total daily energy expenditure) adds everything you do in a day. The small number above is your resting burn, the big one your TDEE.
How many calories should I eat to lose weight?
US obesity guidelines often start with 500 to 750 fewer calories a day than you burn. The calorie deficit calculator works out your number and how many weeks it takes to reach a goal, with the safety limits.
Why do other calculators give a different number?
They use different equations and different activity multipliers. The older Harris-Benedict equation, for example, came out about 5% above measured values in the 1990 study that produced the Mifflin-St Jeor equation used here.
Does it work for teenagers?
No, it’s for adults. The equation was built on people aged 19 to 78, and teens need extra energy to grow, as the Dietary Guidelines for Americans point out. A pediatrician or registered dietitian can help.
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A worked example in stones and feet
A 52-year-old man, 5 ft 10 in and 13 st 7 lb, with an office job and no regular exercise:
- Convert: 5 ft 10 in = 70 in × 2.54 = 177.8 cm. 13 st 7 lb = 189 lb × 0.4536 = 85.7 kg.
- Resting burn: 10 × 85.7 + 6.25 × 177.8 − 5 × 52 + 5 = about 1,714 calories.
- Sedentary (× 1.2): about 2,056 calories a day.
- If he starts walking briskly most days and moves to lightly active (× 1.375): about 2,356.
- The same day in kilojoules: 2,056 × 4.184 = about 8,600 kJ. One kilocalorie is 4.184 kJ, the conversion used by the FAO, WHO and UNU.
The NHS notes that labels show calories under the “energy” heading, often in both kcal and kJ: to go from kJ to calories, divide by 4.184.
Picking your activity level honestly
The activity level moves the result more than anything else: in the example above, the gap between sedentary and very active is about 900 calories a day. The FAO, WHO and UNU report on human energy requirements describes whole lifestyles rather than gym sessions, which is a useful reality check:
- Sedentary or light activity (1.40 to 1.69 × resting burn): for example, urban desk workers who rarely do strenuous tasks.
- Active or moderately active (1.70 to 1.99): for example, people with desk jobs who also exercise moderately to vigorously for about an hour a day, or construction workers.
- Vigorous (2.00 to 2.40): for example, manual farm labourers who work for hours with hand tools and carry heavy loads.
The same report notes that levels above 2.40 are hard to keep up for long. Two practical points follow. First, three gym sessions a week on top of a desk job is closer to the light end than to “very active”. Second, the five multipliers in this calculator are a convention: its 1.2 for “sedentary” is lower than the FAO range for desk workers, so if you walk a lot during the day, “lightly active” may be closer to the truth.
When the number is likely to be off
- Very sedentary days or an unusually low metabolism: the NIH notes that its own calorie estimates may come out too high for these people.
- Logging what you eat: the NIH also notes that people tend to underestimate how much they eat, so a “steady weight” on paper may hide extra intake.
- Under 18, pregnant or breastfeeding: the NIH Body Weight Planner, built on more detailed models, is also not intended for these groups. Ask a doctor, midwife or registered dietitian.
- A medical condition or a special diet for health reasons: the NHS suggests talking to a GP or healthcare professional before counting calories.
How to turn the estimate into your real number
- Eat around the calculated amount for two to three weeks and weigh yourself at the same time of day, a few times a week.
- If the average stays flat, the estimate is close to your real burn.
- If it drifts, size the correction from the trend: using the 7,700-calories-per-kilogram rule, a change of about 1 kg over four weeks means your intake is roughly 275 calories a day away from your real burn.
- For a longer plan that accounts for how your body adapts as weight changes, the free NIH Body Weight Planner simulates your weight over time from the same inputs.
Sources
- FAO, WHO and UNU: Human energy requirements, physical activity levels (Table 5.3)
- FAO, WHO and UNU: Human energy requirements, units of energy (1 kcal = 4.184 kJ)
- NIDDK (NIH): Body Weight Planner
- NHS: Understanding calories
- NHS Better Health: Calorie counting
- NHS: Advice for underweight adults
More questions
How do I convert kilojoules to calories?
Divide by 4.184. One kilocalorie (the “calorie” on food labels) equals 4.184 kJ, so 8,400 kJ is about 2,000 calories.
Which activity level should I choose if I go to the gym three times a week?
If you sit at work the rest of the time, usually lightly active. In the FAO, WHO and UNU report, even a desk job plus about an hour of exercise a day counts only as moderately active.
Why am I gaining weight while eating my calculated calories?
The estimate may be too high for you, or intake may be higher than logged: the NIH notes people tend to underestimate what they eat. Track for a few weeks, then correct by the gap the scale shows.
How many calories should I eat if I want to gain weight?
Start a little above the number shown and watch the trend over a few weeks. If you’re underweight or have lost weight without trying, see a doctor first, because it can be a sign of an underlying condition.