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Browse all calculatorsEstimate the calories your body uses in a day, then see a daily figure for keeping, losing or gaining weight. The working is shown and results update as you type.
Moderate exercise 3 to 5 days a week (x 1.55).
| Goal | Calories a day | Change a day |
|---|
This is a general estimate for educational use. It is not medical advice, a diagnosis or a treatment plan. Talk to a doctor, registered dietitian or other qualified professional before you change your diet, exercise or health care.
Body fat unlocks Katch-McArdle. A goal weight adds a rough time estimate to the goal rows.
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A calorie calculator estimates how many calories your body uses in a day. It works out your basal metabolic rate (BMR) from age, sex, height and weight with a published equation, then multiplies it by an activity factor from 1.2 to 1.9. The result is a maintenance estimate that daily figures for losing or gaining weight are measured from.
Food labels use the word calorie for a kilocalorie (kcal), and so does this page. The calculator shows the maintenance figure first, then a table of estimated daily calories for mild, regular and extreme weight loss and for mild and regular weight gain. Two optional extras are a goal weight, which adds a rough time estimate, and a body fat percentage, which unlocks a third formula. The working for every step is written out under the result. To see how the same BMR turns into energy use at each activity level, try the TDEE calculator.
| Person and formula | BMR | Maintain | Lose 0.5 kg | Gain 0.5 kg |
|---|---|---|---|---|
| Woman, 30 y, 165 cm, 65 kg (Mifflin-St Jeor) | 1,370 | 2,124 | 1,574 | 2,674 |
| Man, 30 y, 180 cm, 80 kg (Mifflin-St Jeor) | 1,780 | 2,759 | 2,209 | 3,309 |
| Same man (revised Harris-Benedict) | 1,854 | 2,873 | 2,323 | 3,423 |
| Same man, 20% body fat (Katch-McArdle) | 1,752 | 2,716 | 2,166 | 3,266 |
| Woman, 50 y, 160 cm, 55 kg, Sedentary (Mifflin-St Jeor) | 1,139 | 1,367 | 1,200 (minimum applied) | 1,917 |
The first answer is already on screen. Change any number and it updates at once, with no Calculate button.
Pick female or male, metric or US units, then type age (18 to 100), weight and height. US units take feet and inches, and the page converts them for you.
Five levels from Sedentary to Extra active, each with its factor and a one-line description of the weekly exercise it stands for.
Maintenance comes first, then the loss and gain rows. A small tag appears next to any figure that was capped or raised to a minimum, with the reason in words underneath.
Open More options to switch the BMR formula, type a body fat percentage for Katch-McArdle, or add a goal weight for a rough time to get there. Then copy the result or share a link.
There are two steps. First an equation turns your body measurements into a BMR, the energy used at rest. Then the BMR is multiplied by an activity factor to allow for movement through the day. All the arithmetic is done in kilograms and centimetres, so pounds are multiplied by 0.45359237 and inches by 2.54 first.
The default equation is Mifflin-St Jeor, published in 1990 from measurements on 498 healthy adults. The revised Harris-Benedict equations from 1984 are offered as a second choice. Katch-McArdle uses lean body mass instead, which is why it needs a body fat percentage. The numbers for each equation are in the table, and the worked examples above use them. Once you have the energy side, the macro calculator shows one way to split a daily figure into protein, carbohydrate and fat.
| Formula | Equation | Source |
|---|---|---|
| Mifflin-St Jeor | Men: 10w + 6.25h – 5a + 5 Women: 10w + 6.25h – 5a – 161 |
Mifflin et al., 1990 |
| Revised Harris-Benedict | Men: 88.362 + 13.397w + 4.799h – 5.677a Women: 447.593 + 9.247w + 3.098h – 4.330a |
Roza and Shizgal, 1984, with coefficients as printed in Pavlidou et al., 2023 |
| Katch-McArdle | 370 + 21.6 x lean body mass, where lean body mass = w x (1 – body fat % / 100) | Irvine Valley College lab text |
| Level | What it stands for | Factor |
|---|---|---|
| Sedentary | Little or no exercise | 1.2 |
| Lightly active | Light exercise 1 to 3 days a week | 1.375 |
| Moderately active | Moderate exercise 3 to 5 days a week | 1.55 |
| Very active | Hard exercise 6 to 7 days a week | 1.725 |
| Extra active | Hard daily exercise plus a physical job, or two sessions a day | 1.9 |
The goal rows use a rough rule of thumb: about 7,700 kcal per kilogram, or 3,500 kcal per pound, of body weight. The daily change is capped at 1,000 kcal.
| Weekly rate | Working | Daily change | Shown as |
|---|---|---|---|
| 0.25 kg a week | 0.25 x 7,700 / 7 | 275 kcal | Loss and gain |
| 0.5 kg a week | 0.5 x 7,700 / 7 | 550 kcal | Loss and gain |
| 1 kg a week | 1 x 7,700 / 7 | 1,100 kcal | Loss only, capped at 1,000 |
| 0.5 lb a week | 0.5 x 3,500 / 7 | 250 kcal | Loss and gain |
| 1 lb a week | 1 x 3,500 / 7 | 500 kcal | Loss and gain |
| 2 lb a week | 2 x 3,500 / 7 | 1,000 kcal | Loss only |
The rule ignores the way the body adapts as weight changes, so real results usually drift from the plan. Hall and colleagues described this in a 2011 Lancet paper. Treat every time estimate as a rough guide, not a forecast.
Many calorie calculators take a few numbers and print a single figure. These are the details that change what the number means.
| Feature | Basic calorie calculator | This calculator |
|---|---|---|
| Results | Often needs a Calculate button | Updates as you type, with an answer on first load |
| Formulas | One, rarely named | Mifflin-St Jeor, revised Harris-Benedict and Katch-McArdle, each with its equation printed |
| Ages | Sometimes includes teenagers | Adults only, 18 to 100; under 18 gets a plain note instead of numbers |
| Low targets | May show any number | Loss targets are raised to a sourced minimum of 1,200 (women) or 1,500 (men) kcal, with a tag and a sentence |
| Large deficits | Uncapped, or silent about it | Daily change capped at 1,000 kcal, and the capped rate is stated |
| Goal weight | Rarely offered | Optional, with a rough time for each row and a note on why it is rough |
| Working | Answer only | Each step written out, including unit conversions and rounding |
| Sources | Few or none | Papers and institutional pages listed with links |
| Sharing | Rare | Copy the result or share a link that opens with the same inputs |
Get a first maintenance figure to compare with what you currently eat or with a figure a dietitian gave you.
Read how many kcal a day a 0.25, 0.5 or 1 kg weekly change represents, and see when the calculator caps or raises it.
Switch between the three equations to see how far apart they land for the same person, then keep the one you can explain.
Type a goal weight for a rough number of weeks at each rate, along with the reminder that real change slows.
Carry a daily figure into the protein calculator or the carbohydrate calculator to see published ranges in grams.
Estimate the energy of one workout with the calories burned calculator and compare it with the daily figure.
Any equation is an estimate. These points show where the calculator can drift from a real person, with figures taken from the calculator itself.
The default woman gets a BMR of 1,370 from Mifflin-St Jeor and 1,430 from revised Harris-Benedict, about 60 kcal a day apart before the activity factor is applied.
It multiplies the whole BMR. For the default woman, moving from 1.375 to 1.55 raises maintenance by about 240 kcal a day, so the level picked changes the answer noticeably.
An 80 kg person at 20% body fat gets a BMR of 1,752; at 30% body fat the same weight gives 1,580, because there is less lean mass.
The figure of 7,700 kcal per kilogram is a convention, not a measurement of any one body, and it is the reason the time estimate is labelled rough.
This page applies the Harvard Health Publishing figures of 1,200 and 1,500 kcal. The NIDDK Body Weight Planner warns that intake must be at least 1,000 calories a day, so published tools differ.
Nothing you type leaves your browser. After the page loads, the calculator keeps working without a connection. For an exact age in years, use the age calculator.
The Mifflin-St Jeor equations were derived from adults aged 19 to 78, so results at the edges of the 18 to 100 range are extrapolated. For anyone under 18, a doctor, dietitian or school nurse can help.
The equations came from measurements on healthy people, and this page does not adjust for pregnancy, breastfeeding, illness or medicines. A doctor or registered dietitian can advise where those apply.
It prints numbers and sources and does not tell anyone what to eat or how fast to change weight. For general information, see the CDC page on steps for losing weight.
Every equation, factor and minimum on this page comes from one of these pages. Where a primary source could not be read in full, the list says what was checked instead.
Short answers about calories, BMR and the weight-goal rows. For all other calculators, see the free online calculators page.
It depends on age, sex, height, weight and how active you are. With the Mifflin-St Jeor equation and a Moderately active level, a 30 year old woman of 165 cm and 65 kg comes out near 2,124 kcal a day for keeping her weight, and a 30 year old man of 180 cm and 80 kg near 2,759. Type your own details to see your estimate.
It uses a published equation to estimate your basal metabolic rate, the energy your body uses at rest, then multiplies it by an activity factor from 1.2 to 1.9 to estimate maintenance calories. The goal figures are the maintenance estimate minus or plus a daily energy change for the chosen weekly rate.
Mifflin-St Jeor is the default. The revised Harris-Benedict equations, and Katch-McArdle once a body fat percentage is typed, can be chosen under More options. The 1990 Mifflin paper reported that the original Harris-Benedict equations overestimated measured resting energy expenditure in its sample, but no equation is exact for every person.
BMR is the energy the body uses at rest to stay alive. Maintenance calories add the energy of movement and exercise, so they are the BMR multiplied by the activity factor. For the default woman the BMR is 1,370 and the maintenance estimate is 2,124.
Pick the description that matches a typical week, from Sedentary at 1.2 to Extra active at 1.9. The factor multiplies the whole BMR, so the choice moves the answer by hundreds of calories: for the default woman, 1.375 gives about 1,884 kcal and 1.55 gives about 2,124.
A common rule of thumb is 3,500 kcal per pound, which is roughly 7,700 kcal per kilogram, and this calculator uses it. A 2011 paper in The Lancet by Hall and colleagues describes the rule as ignoring how the body adapts as weight changes, so real results usually differ from the arithmetic.
On the 3,500 kcal rule of thumb, 3,500 divided by 7 days is 500 kcal a day, and 1 kilogram a week would be 1,100 kcal a day. The CDC describes a gradual, steady pace of about 1 to 2 pounds a week as more likely to keep the weight off.
Harvard Health Publishing says daily intake should not fall below 1,200 for women or 1,500 for men except under the supervision of a health professional. This page raises any loss target to that figure, tags it and explains it in words. Other published tools use different minimums, for example 1,000 in the NIDDK Body Weight Planner.
It divides the difference between current and goal weight by the weekly rate for each row, using the same rule of thumb as the daily figures. Because the rule ignores the way the body adapts, the number of weeks is a rough guide, not a forecast. No time is shown for a goal weight with a BMI under 18.5, which the CDC lists as the underweight range.
The equations were derived from adults, and the Mifflin-St Jeor study measured people aged 19 to 78. Under 18 the page shows a plain note instead of numbers, because energy needs in young people depend on growth. Above 78 the result is an extrapolation.
They may use different equations, different activity factors, different rounding or different minimum limits. On this page the same woman gets a BMR of 1,370 from Mifflin-St Jeor and 1,430 from revised Harris-Benedict, so a gap of tens of calories a day appears before activity is applied.
No. The calculation runs in your browser and nothing is sent to a server. Your numbers appear in the page address only after you change something, so a shared link opens with the same inputs, and your choice of metric or US units is remembered on your own device.