MiniCalci

Calculators & Converters
Health & Fitness

BMI Calculator

Calculate your Body Mass Index (BMI) using metric (cm/kg) or imperial (ft-in/lb) units, plus your WHO weight category. General screening tool only.

What Does This BMI Calculator Do?

This calculator computes your Body Mass Index (BMI) from your height and weight, using either metric (cm/kg) or imperial (ft-in/lb) units, and shows which WHO weight category your BMI falls into.

The BMI Formula

BMI = Weight (kg) / [Height (m)]²

Worked Example: 170 cm, 70 kg

  • Height in meters: 1.70 m
  • Height squared: 1.70 x 1.70 = 2.89
  • BMI = 70 / 2.89 = 24.2 (Normal weight)

BMI Categories (WHO)

  • Under 18.5: Underweight
  • 18.5 - 24.9: Normal weight
  • 25 - 29.9: Overweight
  • 30 and above: Obese

Important Disclaimer

BMI is a general screening tool, not a diagnosis. It doesn't account for muscle mass, bone density, body composition, or other individual health factors, so it can be misleading for athletes, older adults, or people with unusual body composition. Always consult a doctor or qualified healthcare provider for a full, personalized health assessment.

See also the calorie calculator to estimate your daily energy needs.

Frequently Asked Questions

What is BMI?
Body Mass Index (BMI) is a simple screening measure that uses your height and weight to estimate whether you're in an underweight, normal weight, overweight, or obese range, according to World Health Organization (WHO) categories.
How is BMI calculated?
BMI = weight (kg) / height (m) squared. For imperial units, height and weight are first converted to metric before applying the same formula.
What are the BMI categories?
Under 18.5 is Underweight, 18.5-24.9 is Normal weight, 25-29.9 is Overweight, and 30 and above is Obese, according to the standard WHO classification used worldwide.
Is BMI an accurate measure of health?
BMI is a useful general screening tool for populations, but it has real limitations for individuals — it doesn't distinguish between muscle and fat mass, so athletes and very muscular people can show a high BMI despite low body fat. It's not a diagnostic tool.
Does BMI account for age or sex?
The standard adult BMI formula and categories used here do not adjust for age or sex. Some clinical contexts use different reference ranges for children, older adults, or specific populations — consult a doctor for a more personalized assessment.
What should I do if my BMI is outside the normal range?
BMI alone doesn't determine your health status. If you have concerns about your weight or BMI result, consult a doctor or qualified healthcare provider, who can consider your full health picture, not just height and weight.
How do I calculate BMI in imperial units by hand?
BMI = 703 x weight (lb) / [height (in)]². For example, a 154 lb person at 5'7" (67 inches): 703 x 154 / 67² = 703 x 154 / 4489 ≈ 24.1.

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How this is calculated: This tool uses standard, well-established formulas for health & fitness calculations. Results are estimates for informational and planning purposes — always double-check figures for anything with real-world consequences (e.g. ordering materials or submitting grades).