Calorie Calculator
Estimate your daily calorie needs with the Mifflin-St Jeor formula and get targets for maintaining, losing or gaining weight.
Calorie Calculator — input your values
What does this health calculator do?
This calorie calculator estimates your basal metabolic rate (BMR) with the Mifflin-St Jeor equation and multiplies it by an activity factor to find your total daily energy expenditure (TDEE) — the calories needed to maintain your current weight.
It then translates that number into practical targets: maintenance, a mild 250-kcal deficit, a standard 500-kcal deficit for weight loss, and a 500-kcal surplus for weight gain, all in a single table and chart.
These are estimates based on population equations. Individual needs vary with genetics, muscle mass, hormones and daily activity, so treat the numbers as a starting point — and consult a professional before making major dietary changes.
Formula and variables
TDEE = BMR × activity factor, where the factor ranges from 1.2 (sedentary) to 1.9 (extra active).
| Symbol | Meaning |
|---|---|
| w | Weight in kilograms |
| h | Height in centimeters |
| a | Age in years |
Worked example
A 30-year-old man, 175 cm, 75 kg, moderately active (factor 1.55).
- BMR = 10 × 75 + 6.25 × 175 − 5 × 30 + 5 = 1,668.75 kcal.
- TDEE = 1,668.75 × 1.55 = 2,586.6 kcal/day.
- Weight loss target = 2,587 − 500 = 2,087 kcal/day.
- Weight gain target = 2,587 + 500 = 3,087 kcal/day.
Answer: Maintenance ≈ 2,587 kcal/day; about 2,087 kcal/day for weight loss.
Tips and common mistakes
Tips
- Weigh yourself weekly at the same time and adjust your intake by 100–200 kcal based on the trend.
- Food scale portions for a week or two — most people underestimate serving sizes.
- Protein helps preserve muscle during a deficit; aim for about 1.6–2.2 g per kg of body weight.
- Activity factors are rough — a step counter gives a more personalized maintenance estimate over time.
Common mistakes to avoid
- Picking 'extra active' when you only exercise a few times a week — most people are lightly or moderately active.
- Eating the same calories on rest days as on training days without adjusting.
- Dropping calories too aggressively; very low intakes are hard to sustain and can slow progress.
Calorie Calculator — frequently asked questions
How many calories should I eat a day?
It depends on your age, sex, height, weight and activity. The calculator estimates your maintenance calories and then shows you targets for losing or gaining weight.
What is BMR?
Basal metabolic rate is the energy your body burns at complete rest to keep you alive — breathing, circulation and organ function. It's usually the largest part of your daily burn.
How many calories should I eat to lose weight?
A deficit of about 500 kcal per day below maintenance typically produces roughly 0.5 kg of weight loss per week, which is considered a safe, sustainable rate.
What is the Mifflin-St Jeor equation?
It's a widely validated formula for estimating BMR using weight, height, age and sex: 10 × kg + 6.25 × cm − 5 × age, plus 5 for men or minus 161 for women.
Are the results accurate?
These equations are accurate within about 10% for most people. Individual differences in muscle mass and genetics can shift your true needs either way.
Is it safe to eat at a 500-calorie deficit?
For most adults, yes. Avoid going below roughly 1,200 kcal/day for women and 1,500 kcal/day for men, and check with a healthcare provider if you have medical conditions.