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In this article (7 sections)
How do you calculate daily calorie needs?
There is no single calorie target for everyone. The calorie-needs calculator uses a prediction equation and an activity assumption. The result should not be presented as a measurement of your personal energy expenditure.
What determines your calorie needs?
The calculator uses the following inputs:
| Input | Role in the Estimate |
|---|---|
| Weight | Enters the resting-energy equation in kilograms |
| Height | Enters the equation in centimeters |
| Age | Enters the equation in years |
| Sex coefficient | Selects one of the original equation constants |
| Activity assumption | Multiplies predicted resting expenditure |
The formula behind the number
The Mifflin-St Jeor equation predicts resting energy expenditure (REE). The original 1990 study gives these simplified equations:
| Equation Coefficient | Predicted Resting Energy Expenditure (kcal/day) |
|---|---|
| Male | 10 × weight (kg) + 6.25 × height (cm) − 5 × age + 5 |
| Female | 10 × weight (kg) + 6.25 × height (cm) − 5 × age − 161 |
For US measurements, divide pounds by about 2.205 to get kilograms and multiply inches by 2.54 to get centimeters. For example, 154 lb is about 70 kg and 66 in is 167.6 cm. Use total height in inches, not just the inches after feet.
The calculator then applies an activity multiplier: 1.2, 1.375, 1.55, 1.725 or 1.9. These are additional modeling assumptions, not part of the original resting-energy equation or a measurement of exercise. Work, routine movement and training all affect the activity estimate.
Four calculation examples
All numbers below are calculated using the formula above and rounded to the nearest 10 calories:
| Person | Factor 1.2 | Factor 1.375 | Factor 1.55 |
|---|---|---|---|
| Female, 30 years, 65 kg, 168 cm | 1,670 kcal | 1,910 kcal | 2,150 kcal |
| Male, 30 years, 80 kg, 180 cm | 2,140 kcal | 2,450 kcal | 2,760 kcal |
| Female, 50 years, 70 kg, 165 cm | 1,580 kcal | 1,820 kcal | 2,050 kcal |
| Male, 60 years, 85 kg, 178 cm | 2,000 kcal | 2,290 kcal | 2,580 kcal |
For the 30-year-old male example, the chosen activity factors change the rounded estimate from 2,140 to 2,760 kcal. This illustrates sensitivity to an assumption; it does not establish which factor is correct for a particular person.
For a broad explanation of what daily needs mean, see how many calories per day. For exercise accounting, see TDEE and active versus total calories.
And if you want to lose weight?
Weight-management goals require more than subtracting a fixed amount from a calculator result. Individual circumstances and nutritional adequacy matter. See calories for weight loss and calorie deficits for the limitations of those calculations.
When should you not aim for a calorie number?
The formula is designed for healthy adults. If you are under 18, pregnant or breastfeeding, have or have had an eating disorder, are taking medication that affects weight or appetite, or have diabetes or another chronic illness — then talk to your doctor or a registered dietitian before setting a calorie number as a goal. Nothing in this article is medical advice.
Frequently Asked Questions
How many calories should a woman eat per day?
For the female example in the table, age 30, 65 kg and 168 cm gives about 1,910 kcal after applying the assumed 1.375 multiplier. This is a worked example, not a target for all women. Open the calculator.
How many calories should a man eat per day?
For the male example, age 30, 80 kg and 180 cm gives about 2,450 kcal with the assumed 1.375 multiplier. It is not a universal target for men.
What is the difference between BMR and daily calorie needs?
Basal metabolic rate and resting energy expenditure describe energy use under different resting measurement conditions. Mifflin-St Jeor predicts REE; the additional activity multiplier estimates daily expenditure. Neither figure by itself is a minimum safe intake or an individually prescribed target.
Does calorie need decrease with age?
In this equation, increasing age by 20 years while holding other inputs fixed reduces predicted resting expenditure by 100 kcal. After an activity multiplier, the change in predicted daily expenditure is larger. This describes the equation, not an individual's measured change with age.
How accurate is a calculated calorie need?
It is an estimate, not a measurement. Individuals with identical inputs can have different expenditure. The formula does not directly measure body composition or daily activity, and the output has no guaranteed accuracy for a particular person.