BMI Calculator
Calculate your Body Mass Index in seconds with our free BMI Calculator. Instantly see if you’re underweight, normal, overweight or obese and get science-backed health tips
BMI Category Scale
Free Online BMI Calculator
The BMI Calculator lets you work out your Body Mass Index in one click. Simply enter your height and weight, choose metric or imperial units, and learn whether you fall into the under-, normal-, over- or obese weight ranges
How the BMI Formula Works
BMI is weight divided by height squared.
Metric: BMI = weight (kg) ÷ height² (m)
Imperial: BMI = 703 × weight (lb) ÷ height² (in)
Our calculator auto-converts units, removes rounding errors and displays one-decimal-place precision—exactly what clinicians use
BMI Classification Table
| Category | BMI Range (kg/m²) | Health Insight |
|---|---|---|
| Underweight | < 18.5 | Possible nutrient deficiencies |
| Normal | 18.5 – 24.9 | Lowest risk profile |
| Overweight | 25.0 – 29.9 | Raised risk of heart disease |
| Obesity I | 30.0 – 34.9 | Higher risk of type 2 diabetes |
| Obesity II | 35.0 – 39.9 | Greater risk of sleep apnoea |
| Obesity III | ≥ 40 | Severe cardiovascular strain |
Why Knowing Your BMI Matters
A BMI outside the 18.5–24.9 window correlates with elevated chances of hypertension, coronary artery disease and certain cancers . Early awareness helps you seek advice before complications arise.
Who Should Use a BMI Calculator?
Adults 20 + years looking for a quick weight-status screen
Fitness enthusiasts tracking progress
Clinicians needing a fast triage tool
Limitations: BMI doesn’t differentiate muscle from fat and may misclassify athletes, pregnant women or the elderly . Pair it with waist-to-height ratio for deeper insight.
How to Improve a High BMI
Adopt a balanced calorie-controlled diet rich in fibre and lean protein (link: /calorie-calculator).
Aim for 150 minutes of moderate aerobic activity weekly (CDC guideline) .
Strength-train twice a week to preserve muscle mass.
Consult a healthcare professional for personalised goals .
Frequently Asked Questions
Q1. What is a healthy BMI for women?
The normal adult range (18.5–24.9 kg/m²) applies to both sexes .
Q2. Is BMI accurate for bodybuilders?
No. High muscle mass can inflate BMI. Use body-fat calipers or DEXA scans alongside BMI .
Q3. Does age affect BMI interpretation?
Yes. For children and teens, percentiles—not adult cut-offs—should be used