BMI Calculator (Women, Men & Kids)
Free BMI Calculator Online to calculate your Body Mass Index (BMI) for men, women, and kids using age, KG/CM, or LB/FT units. Get Instant BMI results and health insights.
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About BMI Calculator for Men, Women & Kids
This free BMI calculator estimates body mass index from height and weight. Choose Men, Women, or Kids, set age, and switch between Metric (kg/cm), US (lb, ft/in), and UK (st/lb, ft/in) units. Instant guidance shows your category and how much weight to lose or gain toward a healthy range.
How to calculate BMI online
- 1
Choose profile and units
Select Men, Women, or Kids, then pick Metric, US, or UK measurement units.
- 2
Enter age, height, and weight
Add your age and body measurements. Kids mode uses age-based BMI guidance for ages 2–19.
- 3
Read the guidance
Review your BMI category, healthy weight band, and how much to lose or gain to reach a healthier range.
Why use this BMI calculator
Men, Women & Kids
Adult WHO categories plus approximate pediatric BMI guidance by age.
Metric, US & UK units
Switch freely between kg/cm, lb with ft/in, and stone/lb with ft/in.
Lose / gain targets
See a healthy weight range and how much to change to get there.
Clear category guidance
Underweight, healthy, overweight, and obesity explained in plain language.
How BMI Calculator Works - Calculation & Formulas
Body Mass Index (BMI) is a simple height-and-weight screen. This tool uses the standard BMI formula to calculate BMI from your inputs, then maps the result to adult WHO categories or age-based kids guidance.
Metric BMI formula
BMI = weight (kg) ÷ [height (m)]²Example: 70 kg and 1.75 m → 70 ÷ (1.75 × 1.75) ≈ 22.9
Imperial / US formula
BMI = 703 × weight (lb) ÷ [height (in)]²Example: 154 lb and 69 in → 703 × 154 ÷ (69 × 69) ≈ 22.7. The calculator converts lb and ft/in so results stay consistent.
Adult BMI categories (WHO)
Underweight: BMI under 18.5. Healthy weight: 18.5–24.9. Overweight: 25–29.9. Obesity: 30 or higher. These bands apply to the Men and Women profiles.
Kids BMI (ages 2–19)
For children and teens, BMI is interpreted with age and sex rather than fixed adult cutoffs. This tool uses approximate percentile-style bands as a quick screen — a clinician should review official growth charts.
Healthy weight range
From your height, the calculator estimates a weight band that maps to a healthy BMI range, then shows how much to lose or gain to reach it.
Frequently asked questions - FAQs
Quick answers about BMI Calculator.
Yes. You can calculate BMI online for free with no account required.
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