BMI Calculator
It divides weight by height squared to produce Body Mass Index and maps the result to the WHO weight categories.
Body mass index
23.4
Healthy range
129–174 lb
Category
Healthy
Scale
WHO adult
What it calculates
It divides weight by height squared to produce Body Mass Index and maps the result to the WHO weight categories.
Why it matters
BMI is the standard population screening measure used by clinicians as a first indicator of weight-related health risk.
Who it's for
Anyone tracking weight change, and clinicians or coaches needing a fast screening figure.
Formula
- kg
- Body mass in kilograms
- m
- Height in meters
Worked example
82 kg at 1.78 m
- 1Height squared: 1.78² = 3.168
- 2BMI = 82 ÷ 3.168
BMI 25.9 — overweight range (25.0–29.9)
How the bmi calculator works
BMI = kg/m². In imperial units the equivalent is 703 × lb/in². The categories are: under 18.5 underweight, 18.5–24.9 normal, 25.0–29.9 overweight, 30 and above obese.
BMI compares weight to height and is a screening figure, not a diagnosis. It does not distinguish muscle from fat, so athletes often read high.
The healthy band spans 18.5 to 24.9. For your height that is 128.9–173.5 lb.
Common mistakes
- Treating BMI as a body fat measurement — it does not distinguish muscle from fat.
- Applying adult categories to children, who need age-and-sex percentile charts.
- Measuring height in shoes or weight after a large meal.
Tips and best practice
- Pair BMI with waist circumference for a much better risk picture.
- Track the trend over months rather than reacting to a single reading.
Frequently asked questions
What is a healthy BMI?
For most adults, 18.5 to 24.9 is classed as a healthy range by the World Health Organization.
Is BMI accurate for athletes?
Often not. Dense muscle raises weight, so muscular people can score in the overweight range with low body fat.
How do I calculate BMI in pounds and inches?
BMI = 703 × weight(lb) ÷ height(in)². This calculator does it automatically when you switch to imperial.
Does BMI differ by ethnicity?
Yes. Several health bodies use a lower overweight threshold (around 23) for people of South Asian descent.
Can I use BMI during pregnancy?
No. Use pre-pregnancy BMI and follow clinical weight-gain guidance instead.
Related calculators
Further reading
Methodology & trust
- Formula source
- World Health Organization BMI classification.
- Last updated
- 2026-07-28
- Privacy
- Every calculation runs in your browser. No inputs are sent to a server or stored.
- Accessibility
- Keyboard navigable, labeled inputs and WCAG AA color contrast.