Everyday

Calorie Calculator

Estimate how many calories you burn in a day, and so how many keep your weight steady, from your age, height, weight and how active you are.

Enter your age, height and weight to estimate how many calories you need a day.

Estimate. A real-world figure based on the assumptions listed below, which you can change.

How this calculator works

Your daily calorie needs have two parts. Resting energy, often called BMR, is what your body burns at complete rest to breathe, circulate blood and keep warm. On top of that is everything you do, from walking to the car to a workout. The calculator estimates the first and multiplies it by an activity level for the second.

Resting energy comes from the Mifflin-St Jeor equation, published in 1990 from measurements of 498 healthy adults. A systematic review by the American Dietetic Association found it the most reliable of the common equations: it came within 10% of measured resting energy for more people than any other, with the narrowest range of errors.

The activity levels are the ones the National Academies set out in 2023 from doubly labeled water studies, which measure the energy people actually burn over days of normal life. Each comes with a concrete example of a day, so you can pick the one that matches yours. Inactive (× 1.4) is daily living only; very active (× 2.05) is about two hours of exercise on top.

The result is the number of calories that would keep your weight where it is. Turn on the macronutrient split to see it as grams of carbohydrate, protein and fat, checked against the ranges the National Academies recommend for adults.

The formula

Exactly what happens to your numbers, step by step.

Resting energy (Mifflin-St Jeor)

women: 10 × kg + 6.25 × cm − 5 × age − 161
men:   10 × kg + 6.25 × cm − 5 × age + 5

Daily calories

resting energy × activity level
inactive 1.4 · low active 1.6
active 1.75 · very active 2.05

Macronutrients

grams = calories × share ÷ calories per gram
4 for carbohydrate and protein, 9 for fat

A worked example

A 35-year-old woman, 5′6″ and 150 lb, who walks for about an hour most days.

What you enter

Sex: Female
Age: 35
Height: 5 ft 6 in (167.64 cm)
Weight: 150 lb (68.04 kg)
Activity level: Low active

Step by step

Resting energy: 10 × 68.04 + 6.25 × 167.64 − 5 × 35 − 161 ≈ 1,392 calories
Activity level: Low active: × 1.6
Daily calories: 1,392 × 1.6 ≈ 2,230

About 2,230 calories a day to maintain her weight

Many calculators would put her at about 1,910, using a "lightly active" multiplier of 1.375. Those common multipliers, 1.2 to 1.9, have no published source, and they run below the energy the National Academies measured in people with days like hers.

Daily calories, worked out

Common questions, each answered with the Mifflin-St Jeor equation and the National Academies activity levels.

1.How many calories should a 30-year-old woman who is 5′4″ and 140 lb eat a day?
1. Resting energy: 10 × 63.50 kg + 6.25 × 162.6 cm − 5 × 30 − 161 ≈ 1,340 calories.
2. At a low active level (× 1.6): 1,340 × 1.6 ≈ 2,140.
About 2,140 calories a day to maintain her weight.
2.How many calories does an active 40-year-old man who is 5′10″ and 180 lb need?
1. Resting energy: 10 × 81.65 kg + 6.25 × 177.8 cm − 5 × 40 + 5 ≈ 1,733 calories.
2. Active (× 1.75): 1,733 × 1.75 ≈ 3,030.
About 3,030 calories a day.
3.What is the BMR of a 25-year-old man who is 6′0″ and 170 lb?
1. Resting energy: 10 × 77.11 kg + 6.25 × 182.9 cm − 5 × 25 + 5 ≈ 1,794 calories.
About 1,794 calories a day at complete rest, or about 2,510 with daily living (× 1.4).
4.How many calories does an inactive 60-year-old woman who is 5′3″ and 160 lb need?
1. Resting energy: 10 × 72.57 kg + 6.25 × 160.0 cm − 5 × 60 − 161 ≈ 1,265 calories.
2. Inactive (× 1.4): 1,265 × 1.4 ≈ 1,770.
About 1,770 calories a day.
5.How many grams of protein is 20% of 2,000 calories?
1. 20% of 2,000 calories is 400 calories.
2. Protein has 4 calories per gram, so 400 ÷ 4 = 100.
100 grams of protein a day.

Heights and weights are converted at exactly 2.54 cm per inch and 0.45359237 kg per pound, and shown to two decimal places of a kilogram and one of a centimeter. Daily calories are rounded to the nearest 10: the equation is an estimate, and even the best one comes within 10% of measured resting energy for most people, not all, so a figure to the single calorie would claim precision it does not have.

Assumptions

Every result here rests on these. Change your inputs and the result changes with them.

You are an adult (18 or over) and not pregnant or breastfeeding, both of which raise calorie needs.
Your weight is steady. The result is the intake that would keep it that way, not a plan for losing or gaining.
The activity level describes a typical day, averaged over a week.

What this cannot tell you

Every equation is an estimate. Two people with the same age, height and weight can differ by several hundred calories, mostly because of differences in muscle. Only measurement (indirect calorimetry) gives your own figure.
Very muscular people, people with obesity, older adults and some ethnic groups were under-represented in the studies, and the equation may be further off for them.
It is not medical or dietary advice. For a medical condition, weight-loss goal or eating disorder, talk to a doctor or registered dietitian.
To plan a change in weight over time, use the NIH Body Weight Planner, which models how your needs shift as your weight does.

Questions people ask

How many calories should I eat a day?

To keep your weight steady, about as many as you burn. For a 35-year-old woman who is 5′6″, 150 lb and lightly active that is roughly 2,230; for an active 40-year-old man who is 5′10″ and 180 lb, roughly 3,030. Enter your own details above. Your real number can differ by a few hundred calories either way.

What is the difference between BMR and TDEE?

BMR (basal or resting metabolic rate) is what you burn at complete rest. TDEE (total daily energy expenditure) is everything you burn in a day, including movement and digesting food. TDEE is BMR times an activity level, and it is the number to compare with what you eat.

Why is this higher than other calorie calculators?

Most calculators multiply BMR by 1.2 for a "sedentary" person. That figure has no published source, and studies that measure the energy people actually burn rarely find adults that low. This calculator uses the National Academies activity levels instead, which start at 1.4 for daily living with no exercise.

How many calories should I eat to lose weight?

Fewer than the number here, but the old rule that cutting 3,500 calories loses a pound overstates how fast weight comes off, because your needs fall as you lose weight. The NIH Body Weight Planner models that properly. Very low intakes should be supervised by a doctor.

How accurate is the Mifflin-St Jeor equation?

It is the most accurate of the common equations for healthy adults, but it is still an estimate. In the American Dietetic Association review it came within 10% of measured resting energy for more people than any other equation, and errors larger than that do happen.

Sources and review

Sources

Methodology version 1.0.0 · Last reviewed October 12, 2026

Cite this calculator

For coursework, a resource list or your own site. How every calculator is built and checked is set out on the methodology page.

Citation

Chalk Calculator. (2026, October 12). Calorie Calculator (Methodology version 1.0.0). https://chalkcalculator.com/calorie-calculator/

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