BMI Calculator

Estimate your bmi from the values you enter. The calculation runs entirely in your browser using published formulas, so your weight, height, age, sex, and activity level are never sent to our servers.

Enter your details above to see an estimate with a plain-language explanation of what it means and its limitations. The result is general information, not a medical assessment.

BMI CalculatorCalorie Calculator
Calorie/BMI Calculator

Understanding Your Results

BMI compares your weight with your height and places you in a broad weight category. It is a quick screening measure, not a diagnosis, and it cannot distinguish muscle from fat — so it can be misleading for athletes, older adults, and some other groups.

The calorie estimate uses the Mifflin-St Jeor equation to approximate your basal metabolic rate, then applies a standard activity multiplier. Individual needs vary with genetics, body composition, and metabolism, so treat the number as a starting reference rather than a target. For personal guidance, consult a qualified healthcare professional.

How this calculator works

These results are estimates produced by the formulas below. They are provided for general information and are not professional financial or medical advice.

Formula

BMI = weight(kg) / height(m)²
BMR (male) = 10 × weight(kg) + 6.25 × height(cm) − 5 × age + 5
BMR (female) = 10 × weight(kg) + 6.25 × height(cm) − 5 × age − 161
Estimated daily calories = BMR × activity multiplier

weight
Body weight in kilograms (kg).
height
Height in centimetres (cm). It is divided by 100 to give metres for the BMI formula.
age
Age in years.
BMR
Basal Metabolic Rate: the kilocalories (kcal) your body uses at rest.
activity multiplier
A factor from 1.2 to 1.9 applied to BMR to estimate total daily energy use.

Worked example

BMI: 70 kg and 170 cm → 70 ÷ (1.70 × 1.70) = 24.2, which falls in the “Normal weight” category (18.5-24.9).

Calories: a 30-year-old male, 80 kg, 180 cm, moderately active → BMR = 10×80 + 6.25×180 − 5×30 + 5 = 1780 kcal. Multiply by 1.55 → 2759 kcal per day.

What the result includes

  • A BMI value and its WHO weight category (underweight, normal weight, overweight, or obesity).
  • An estimated Basal Metabolic Rate using the Mifflin-St Jeor equation.
  • An estimated total daily calorie figure for the selected activity level.
  • Standard activity multipliers: sedentary ×1.2 (little or no exercise), lightly active ×1.375 (light exercise 1-3 days/week), moderately active ×1.55 (moderate exercise 3-5 days/week), very active ×1.725 (hard exercise 6-7 days/week), extra active ×1.9 (very hard exercise or a physical job).

What the result excludes

  • Clinical measurements such as body-fat percentage, waist circumference, or muscle mass.
  • A medical diagnosis, treatment plan, or prescribed calorie target.
  • Adjustments for pregnancy, lactation, illness, or medical conditions.
  • Imperial (lb/in) units — this version accepts metric units only.

Assumptions and limitations

  • BMI is a screening measure and does not distinguish muscle from fat; muscular or athletic people can have a high BMI without excess body fat.
  • BMI categories follow World Health Organization thresholds and are intended for adults; they are not diagnostic.
  • Calorie estimates use the Mifflin-St Jeor equation, which is a population average; individual needs commonly vary by about 10-20%.
  • The estimate assumes a generally healthy adult who is not pregnant and has no condition that alters metabolic rate.
  • Results are general information and not medical advice. Consult a qualified healthcare professional before acting on them.

References

Formulas last reviewed against the sources above on 2026-10-08. No credentialed professional reviewer was involved.

Frequently Asked Questions

What does my BMI number actually mean?

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BMI (Body Mass Index) compares your weight with your height and places you in a broad category: under 18.5 is underweight, 18.5-24.9 is normal weight, 25-29.9 is overweight, and 30 or higher is obesity. It is a screening measure, not a diagnosis, and it does not account for muscle mass or body composition, so athletes and very muscular people can have a high BMI without excess body fat.

How close is the calorie estimate to my actual needs?

Click to expand

The calorie figure uses the Mifflin-St Jeor equation to estimate your Basal Metabolic Rate (BMR), then applies a standard activity multiplier. It is a population-based estimate rather than a measurement of your individual metabolism, so real needs commonly differ by roughly 10-20% depending on genetics, body composition, and other factors. Treat the result as a general reference, not a precise target.

Can this calculator tell me how many calories to eat to lose weight?

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No. It estimates the energy your body may use per day and does not prescribe a diet or a calorie target. Body weight is influenced by many factors, and changing it safely depends on your personal circumstances. If weight is a concern for you, speak with a qualified healthcare professional or registered dietitian rather than acting on this estimate alone.

Should I use BMI or the calorie estimate?

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The two tools describe different things. BMI is a quick screening measure of weight relative to height, while the calorie estimate approximates daily energy use. Both are general information rather than personal medical advice. If you have health concerns, combine your results with guidance from a qualified healthcare professional.

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