How to use the calorie calculator
- Pick your units and enter your sex, age, height and current weight.
- Choose the activity level that matches a typical week. If you are between two levels, pick the lower one — most people overestimate how active they are.
- Read your results. The headline number keeps your weight steady; the targets below it are for mild loss, loss and mild gain.
The Mifflin-St Jeor equation
Your basal metabolic rate (BMR) is the energy your body uses at complete rest to breathe, circulate blood and keep your organs working. This calculator estimates it with the equation published by Mark Mifflin, Sachiko St Jeor and colleagues in 1990:
- Men: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age (years) + 5
- Women: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age (years) − 161
A 2005 review in the Journal of the American Dietetic Association compared the common prediction equations against measured resting metabolism and found Mifflin-St Jeor the most reliable of them for healthy adults, which is why many dietitians now prefer it to the older Harris-Benedict equation.
BMR is then multiplied by an activity factor to estimate your total daily energy expenditure — the calories you burn on a normal day, including exercise, everyday movement and digesting food:
| Activity level | Description | Factor |
|---|---|---|
| Sedentary | Desk job, little or no exercise | 1.2 |
| Lightly active | Light exercise 1–3 days a week | 1.375 |
| Moderately active | Moderate exercise 3–5 days a week | 1.55 |
| Very active | Hard exercise 6–7 days a week | 1.725 |
| Extra active | Very hard training or a physical job | 1.9 |
Worked example
A 30-year-old man who weighs 80 kg (about 176 lb) and is 180 cm (about 5 ft 11 in) tall:
BMR = 10 × 80 + 6.25 × 180 − 5 × 30 + 5 = 800 + 1,125 − 150 + 5 = 1,780 calories. If he is moderately active, his maintenance level is 1,780 × 1.55 ≈ 2,759 calories a day. Eating about 2,259 calories (500 fewer) would be expected to produce a loss of roughly 1 pound a week at first.
Calorie targets for losing or gaining weight
The targets assume the old rule of thumb that about 3,500 calories equals one pound of body fat, an estimate that dates back to work by Max Wishnofsky in 1958. It is only an approximation. As you lose weight your body needs fewer calories and adapts in other ways, so weight loss usually slows over time even if you keep eating the same amount. The NIH Body Weight Planner models this in more detail.
- Go gradually. The CDC notes that people who lose about 1 to 2 pounds a week are more likely to keep the weight off.
- Respect a floor. A commonly cited guideline is not to eat fewer than about 1,200 calories a day for women or 1,500 for men without medical supervision. The calculator warns you when a target falls below that level.
- Check and adjust. Track your weight for two to three weeks. If it is not moving the way you expect, adjust your intake by 100–200 calories and reassess.
Limitations
Any equation gives an estimate for an average person with your measurements. Your real needs can differ because of muscle mass, genetics, medical conditions such as thyroid disorders, and some medications. The equation is not designed for pregnancy or breastfeeding, when energy needs rise, or for children and teens who are still growing.
When to see a professional
Talk to your doctor or a registered dietitian before changing your diet if you are pregnant or breastfeeding, have diabetes, kidney disease or another chronic condition, take medication that affects appetite or weight, or have a history of disordered eating.
Important: results are estimates for general information only and are not medical advice. They cannot replace an assessment by a doctor, registered dietitian or other qualified health professional.
Frequently asked questions
What is the difference between BMR and maintenance calories?
BMR is what your body burns at complete rest. Maintenance calories (total daily energy expenditure) add the energy used for movement, exercise and digestion, so they are always higher than BMR.
How many calories should I cut to lose a pound a week?
The traditional estimate is about 500 calories a day, based on 3,500 calories per pound of fat. Real results vary and loss tends to slow as your weight drops.
Which activity level should I choose?
Choose the one that matches a normal week, not your best week. If you sit most of the day and exercise three times a week, “lightly active” or “moderately active” usually fits. When unsure, pick the lower level.
Why am I not losing weight at the calculated target?
The equation is an estimate and can be off for an individual, food portions are easy to underestimate, and water weight can hide fat loss for a week or two. Track for several weeks, then adjust by 100–200 calories.
Is Mifflin-St Jeor better than Harris-Benedict?
The Harris-Benedict equation dates from 1919 and was revised in 1984. In comparisons with measured metabolism, Mifflin-St Jeor has generally been more accurate for today’s adults, so it is the default here.
Last updated: October 8, 2026