Daily Calorie Calculator for Weight Loss or Gain

How to use it

Choose Metric or Imperial, then select your sex and enter your age.
Enter your Height and Weight, or the feet, inches and pounds fields if you chose imperial.
Choose your Activity level and your Goal. Add a Body fat figure only if you know it.
Read the Daily calorie target, then the grams of protein, fat and carbohydrate in the table.

How the figures are calculated

Your resting energy (BMR) is the energy your body uses at rest. This calculator uses the Mifflin-St Jeor equation, published in 1990 by Mifflin, St Jeor and colleagues in the American Journal of Clinical Nutrition: 10 times your weight in kilograms, plus 6.25 times your height in centimetres, minus 5 times your age in years, plus 5 for men and minus 161 for women.

Your daily need (TDEE) is the BMR multiplied by an activity factor from 1.2 for little exercise to 1.9 for very hard exercise or a physical job. The factors are commonly used estimates, not measurements.

The target adds or takes away calories for your goal. About 7,700 kcal is commonly taken as the energy in one kilogram of body fat, so losing 0.5 kg a week means about 550 kcal less each day.

When you enter body fat, the page also shows the Katch-McArdle figure, 370 + 21.6 x lean body mass in kg, from McArdle, Katch and Katch, Exercise Physiology (5th edition, 2001). It is shown for comparison only and does not change the target.

These figures are estimates for information only. They are not medical advice: talk to a doctor before you change your diet or exercise, especially if you are pregnant, ill or take medicine.

BMR, men    = 10 x kg + 6.25 x cm - 5 x years + 5
BMR, women  = 10 x kg + 6.25 x cm - 5 x years - 161
TDEE        = BMR x activity factor
Target      = TDEE + (kg a week x 7,700) / 7

Why the target never falls below 1,200 or 1,500 kcal

The NHS describes a very low calorie diet as one of under 800 or 1,200 calories a day, and says such diets are not suitable or safe for everyone. This calculator therefore never sets a target below 1,200 kcal for women or 1,500 kcal for men. If the figure would be lower, it is raised to the minimum and a note tells you.

Women: no target below 1,200 kcal a day.
Men: no target below 1,500 kcal a day.
A lower intake needs a doctor's advice.

Protein, fat and carbohydrate

The table splits the target into 20% protein, 30% fat and 50% carbohydrate. The grams follow from the energy in each: about 4 kcal per gram of protein and of carbohydrate, and 9 kcal per gram of fat.

The Institute of Medicine's report on macronutrients (2005) defines Acceptable Macronutrient Distribution Ranges, given as a percentage of energy for fat, carbohydrate and protein. The split here is one balanced example; a dietitian can set the split for you.

What this calculator does not include

Illness, medicines, pregnancy and breastfeeding, which all change energy needs.
Heavy training: athletes can need far more than the top activity factor.
Body composition beyond the optional body fat figure, which only adds the Katch-McArdle resting energy.

Worked example: 35-year-old woman, 165 cm, 65 kg

The resting energy is 10 x 65 + 6.25 x 165 - 5 x 35 - 161 = 1,345 kcal a day.

With moderate activity (factor 1.55) the daily need is 1,345.25 x 1.55 = 2,085 kcal. Losing 0.5 kg a week takes 550 kcal a day off that, so the target is 1,535 kcal.

The split gives 307 kcal of protein (77 g), 461 kcal of fat (51 g) and 767 kcal of carbohydrate (192 g).

Step	Result
Resting energy (BMR)	1,345 kcal
Daily need (TDEE), moderate activity	2,085 kcal
Target for losing 0.5 kg a week	1,535 kcal

Frequently asked questions

What is the difference between BMR and TDEE?

BMR is the energy your body uses at rest for breathing, circulation and keeping warm. TDEE adds the energy of your daily activity and exercise, so it is the intake that keeps your weight steady.

Why is my target never below 1,200 or 1,500 kcal?

The NHS says very low calorie diets are under 800 or 1,200 calories a day and not suitable or safe for everyone. The calculator raises a lower target to 1,200 kcal for women or 1,500 kcal for men and shows a note.

How exact is the 7,700 kcal per kilogram rule?

It is a rough rule of thumb. Real weight change depends on water, muscle and how the body adapts to a lower intake, so weight can change faster or slower than the number predicts.

Why does the target not change when I enter body fat?

The target uses the Mifflin-St Jeor figure, which needs only height, weight, age and sex. The Katch-McArdle figure uses lean body mass and is shown next to it for comparison.

Can I use the protein, fat and carbohydrate grams as my own plan?

They are one balanced example, not a plan for you. Needs depend on health, training, pregnancy and medicines, so a dietitian or doctor can set the right amounts.

Are my figures sent to a server?

No. The calculation runs in your browser and nothing you enter is sent to us.

Sources

Figures and text last checked on Tuesday, November 10, 2026.

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