Everyday Tools
Calorie / BMR Calculator
Estimate the calories your body burns at rest and across a typical day, using the Mifflin-St Jeor equation.
Calculation inputs
Height and weight can be entered in metric or imperial units.
Results
No result yet
Complete the fields and select Calculate to show results here.
Estimates only, for general information. Not medical or nutritional advice.
About this calculator
This tool estimates your basal metabolic rate, the calories your body burns at rest, and then scales that number up based on how active you are day to day. People use it to set a starting calorie target for weight loss, maintenance, or muscle gain.
How the calculation works
- Men: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age + 5
- Women: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age − 161
- Daily calories = BMR × activity multiplier (1.2 to 1.9)
Notes and assumptions
Mifflin-St Jeor is the most widely used estimate, but individual metabolism varies by body composition, genetics, and medication.
How it works in plain English
Basal metabolic rate, or BMR, is the energy your body needs just to keep breathing, circulating blood, and running basic cell repair while completely at rest. The calculator uses the Mifflin-St Jeor equation, which combines your weight, height, age, and sex into a single formula, because those four factors explain most of the variation in resting metabolism between people.
Weight and height feed in directly, age is subtracted because metabolism slows gradually over the years, and sex adjusts the baseline because men typically carry more lean muscle mass, which burns more calories than fat tissue even at rest.
BMR alone only covers being still in bed all day, so the calculator multiplies it by an activity factor that accounts for exercise, walking, and general movement, producing an estimated total daily energy expenditure, or TDEE. That TDEE is the number most people actually use to plan calorie intake.
The formula
- Men: BMR = 10 x weight(kg) + 6.25 x height(cm) - 5 x age + 5
- Women: BMR = 10 x weight(kg) + 6.25 x height(cm) - 5 x age - 161
- Daily calories = BMR x activity multiplier
Worked example
Consider a 35-year-old man who is 5 feet 9 inches (about 175 cm) tall and weighs 170 pounds (about 77 kg). His BMR works out to 10 x 77 + 6.25 x 175 - 5 x 35 + 5, which equals 770 + 1,094 - 175 + 5, or roughly 1,694 calories at rest. If he is moderately active, exercising three to five days a week, the calculator multiplies that by 1.55, giving an estimated daily need of about 2,626 calories to maintain his current weight. If his goal is gradual weight loss, he might subtract roughly 500 calories from that maintenance figure, aiming for about 2,126 calories a day, a deficit commonly associated with losing around one pound per week. If instead his job changes and he becomes only lightly active, the multiplier drops to 1.375, lowering his estimated maintenance calories to about 2,330 per day even though his BMR itself has not changed at all.
Activity multipliers used in the Mifflin-St Jeor calculation
| Activity level | Description | Multiplier |
|---|---|---|
| Sedentary | 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 | Physical job or twice-daily training | 1.9 |
Multipliers follow the widely used Harris-Benedict/Mifflin-St Jeor activity scale.
Frequently asked questions
How accurate is the Mifflin-St Jeor equation?
It is considered one of the more reliable predictive equations for resting metabolism in healthy adults, typically landing within about 10 percent of measured values. It is still an estimate, not a lab measurement, so actual metabolism can vary based on muscle mass, genetics, and hormone levels.
Should I eat exactly at my calculated calorie number?
Treat it as a starting point rather than an exact target. Weight change over two to three weeks tells you more than the formula alone, so adjust intake up or down based on how your weight actually trends once you start tracking.
Why does the calculator ask for activity level separately from BMR?
BMR only reflects energy burned at complete rest, similar to lying in bed all day. Movement, exercise, and even fidgeting burn additional calories, so the activity multiplier scales the resting number up to reflect a realistic full day.
Does this calculator account for muscle mass directly?
Not directly. It uses weight, height, age, and sex as proxies for body composition, so two people of the same weight but very different muscle-to-fat ratios will get the same estimate even though their true metabolic rates differ somewhat.
Is this safe to use for weight loss planning?
It is a general planning tool, not medical advice. Extreme or fast weight loss goals, pregnancy, certain medical conditions, or eating disorders all call for guidance from a qualified healthcare provider rather than relying on a calculator alone.