Maintenance
- Input
- Man, 30, 80 kg, 180 cm, moderate
- Output
- BMR 1,780 · TDEE 2,759 kcal
The maintenance figure. Eating at this level should hold weight steady over a period of weeks.
Calorie Calculator
A calorie calculator estimates how much energy your body uses in a day. Mifflin-St Jeor is the default equation because the American Dietetic Association's evidence review found it lands within 10% of measured resting metabolic rate more often than the older Harris-Benedict. Katch-McArdle is offered as well, since it uses lean mass and is more accurate for lean, muscular people where the others under-predict.
Runs entirely in your browser — your figures are never uploaded.
How many calories do I need a day?
Daily needs are basal metabolic rate multiplied by an activity factor. A 30-year-old man weighing 80 kg at 180 cm has a BMR of 1,780 kcal; moderately active, that gives about 2,759 kcal a day to maintain weight.
These are estimates for general information, not medical or dietary advice. Consult a doctor or registered dietitian before making significant changes to your diet.
years
kg
cm
kg/week
Negative to lose, positive to gain. 0.5 kg a week is a common sustainable rate.
Daily calorie target
2,209 kcal
to lose 0.5 kg a week
- BMR
- 1,780 kcal
- TDEE
- 2,759 kcal
- Daily adjustment
- −550 kcal
At complete rest
Maintenance
Macronutrient split
%
%
%
- Protein
- 166 g
- Carbs
- 221 g
- Fat
- 74 g
4 kcal per gram
4 kcal per gram
9 kcal per gram
The maths
Calorie Calculator formula
Formula
BMR (Mifflin-St Jeor) = 10 × kg + 6.25 × cm − 5 × age + 5 (men) or − 161 (women) · TDEE = BMR × activity factor
- kg
- Body weight in kilograms
- cm
- Height in centimetres
- age
- Age in years
- activity factor
- 1.2 sedentary to 1.9 extremely active
Worked example
A 30-year-old man, 80 kg, 180 cm, moderately active
Inputs
- Weight
- 80 kg
- Height
- 180 cm
- Age
- 30
- Activity
- Moderate (1.55)
Working
- BMR = 10 × 80 + 6.25 × 180 − 5 × 30 + 5
- = 800 + 1,125 − 150 + 5 = 1,780 kcal
- TDEE = 1,780 × 1.55
2,759 kcal a day to maintain. For 0.5 kg a week of loss, subtract 550 kcal to give about 2,209.
How to
How to use the Calorie Calculator
- 1
Enter your details
Age, sex, height and weight. These four inputs determine basal metabolic rate — the energy used at complete rest.
- 2
Pick an activity level
Choose honestly. Most people overestimate; a desk job with three gym sessions a week is 'moderately active', not 'very active'.
- 3
Set a rate of change
Enter the weekly weight change you want. This is converted to a daily calorie adjustment using roughly 7,700 kcal per kilogram.
- 4
Read the macro split
The daily target is divided into protein, carbohydrate and fat in grams, which is more usable than percentages when planning meals.
Reference
Activity multipliers
| Level | Multiplier | Typical pattern |
|---|---|---|
| Sedentary | 1.2 | Desk work, little deliberate exercise |
| Lightly active | 1.375 | Light exercise 1–3 days a week |
| Moderately active | 1.55 | Moderate exercise 3–5 days a week |
| Very active | 1.725 | Hard exercise 6–7 days a week |
| Extremely active | 1.9 | Physical job or twice-daily training |
Examples
Calorie Calculator examples
Losing half a kilo a week
- Input
- Same person, −0.5 kg/week
- Output
- 2,209 kcal a day
A 550 kcal daily deficit, since a kilogram of body fat is roughly 7,700 kcal. Sustainable for most people.
Formula comparison
- Input
- Same person, all three equations
- Output
- Mifflin 1,780 · Harris 1,854 · Katch 1,839 at 15% fat
Roughly 4% between them. Mifflin is the general default; Katch is better when body fat is known and low.
Why use it
What the Calorie Calculator gives you
The best-evidenced equation by default
Mifflin-St Jeor outperforms Harris-Benedict in validation studies, and all three are available so results can be compared.
Targets as a weekly rate
Expressing the goal as kilograms per week rather than an abstract deficit makes an unrealistic target immediately obvious.
Macros in grams
Percentages are hard to act on. Grams of protein, carbohydrate and fat translate directly into meal planning.
Nothing recorded
Body measurements are never transmitted or stored.
Good to know
Calorie Calculator limitations
- All BMR equations are estimates. Individual metabolic rate varies by 10% or more from the predicted figure even in healthy adults.
- Activity multipliers are coarse. Two people at the same nominal level can differ by several hundred calories a day.
- The 7,700 kcal per kilogram figure is an approximation, and the body adapts to sustained deficits by reducing expenditure.
- Not appropriate for children, during pregnancy or breastfeeding, or for anyone with a medical condition affecting metabolism.
Summary
Calorie Calculator in short
- BMR (Mifflin-St Jeor) = 10 × kg + 6.25 × cm − 5 × age, +5 for men and −161 for women.
- TDEE = BMR × an activity factor from 1.2 to 1.9.
- About 7,700 kcal equals one kilogram of body fat.
- A 550 kcal daily deficit gives roughly 0.5 kg a week.
- Estimates vary by 10% or more between individuals.
FAQ
Calorie Calculator questions
How many calories should I eat a day?
It depends on your basal rate and activity. A moderately active 30-year-old man of 80 kg and 180 cm needs about 2,759 kcal to maintain weight, and roughly 2,209 to lose half a kilogram a week.
What is the difference between BMR and TDEE?
BMR is what your body uses at complete rest to run its basic functions. TDEE adds everything else — moving, digesting, exercising — by multiplying BMR by an activity factor between 1.2 and 1.9.
Which BMR formula is most accurate?
Mifflin-St Jeor for the general population; the American Dietetic Association's review found it within 10% of measured rates more consistently than Harris-Benedict. Katch-McArdle is better if you know your body fat percentage and are lean.
How big a calorie deficit is safe?
A deficit of 500–750 kcal a day, giving roughly 0.5–0.75 kg a week, is commonly recommended. Larger deficits increase muscle loss and are harder to sustain, and intakes below about 1,200 kcal warrant medical supervision.
Which activity level should I choose?
Most people pick too high. A desk job with three or four gym sessions a week is 'moderately active' at 1.55. 'Very active' at 1.725 means hard training six or seven days a week, not occasional exercise.
What macronutrient split should I use?
A common starting point is 30% protein, 40% carbohydrate and 30% fat, adjusted to preference and goal. Protein and carbohydrate provide 4 kcal per gram and fat 9, which is how grams are derived from the split.
Why has my weight loss stopped?
As weight falls, both BMR and the energy cost of movement fall with it, so the original target becomes maintenance. Recalculating at your current weight usually explains a plateau.
How accurate are these numbers?
They are estimates with a genuine margin of error — individual metabolic rate can differ from prediction by 10% or more. Use the figure as a starting point and adjust based on what actually happens over three to four weeks.
Is my health data uploaded?
No. Age, weight and height are used for a calculation in your browser and never sent anywhere. Nothing is stored, logged or associated with you.
Sources
- Mifflin MD, St Jeor ST et al., American Journal of Clinical Nutrition, 1990
- Roza AM, Shizgal HM — revised Harris-Benedict, 1984
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