BMI Calculator
Check your body mass index instantly. Enter your height and weight to see your BMI, category, healthy weight range, and visual gauge.
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Your BMI Results
Your BMI
23.6
Category
Normal
Healthy Weight Range
125 – 169 lb
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How to Calculate Your BMI
Body Mass Index (BMI) is a simple screening tool that estimates body fat based on your height and weight. Our free online BMI calculator gives you an instant result with a colour-coded gauge so you can see where you fall on the spectrum at a glance.
To use the calculator, choose Imperial (feet/inches & pounds) or Metric (centimetres & kilograms), enter your height and weight, and your BMI updates in real time. The result includes your numeric BMI value, the WHO category (Underweight, Normal, Overweight, or Obese), and the healthy weight range for your specific height.
BMI Formula & Categories
The BMI formula in metric units is:
BMI = weight (kg) ÷ height (m)²
For imperial units the equivalent is:
BMI = (weight (lb) × 703) ÷ height (in)²
The World Health Organization classifies adult BMI as follows:
- Underweight: BMI < 18.5
- Normal weight: BMI 18.5 – 24.9
- Overweight: BMI 25.0 – 29.9
- Obese: BMI ≥ 30.0
What Is a Healthy BMI?
A healthy BMI for most adults falls between 18.5 and 24.9. Within this range you have the lowest statistical risk of weight-related conditions such as heart disease, type 2 diabetes, and high blood pressure. Our calculator also shows exactly how much you would need to weigh to reach the normal range at your current height.
Keep in mind that BMI is a screening metric, not a diagnostic tool. It doesn't account for muscle mass, bone density, or body composition. Athletes, pregnant women, and the elderly may need more tailored assessments. Always consult a healthcare provider for personalised advice.
Frequently Asked Questions
How is BMI calculated?
BMI is calculated by dividing your weight in kilograms by your height in metres squared: BMI = kg / m². For imperial units, the formula is (weight in pounds × 703) / (height in inches)². Our calculator handles both unit systems automatically.
What are the BMI categories?
The World Health Organization (WHO) defines four categories: Underweight (BMI below 18.5), Normal weight (18.5–24.9), Overweight (25–29.9), and Obese (30 or above). Our calculator shows your category instantly with a colour-coded gauge.
What is a healthy BMI for adults?
A BMI between 18.5 and 24.9 is considered healthy (normal weight) for most adults. This range is associated with the lowest risk of weight-related health problems. The calculator also shows the exact healthy weight range for your specific height.
Is BMI accurate for athletes and muscular people?
BMI does not distinguish between muscle and fat mass. Athletes or people with high muscle mass may have a high BMI despite being healthy. BMI is best used as a general screening tool — consult a healthcare professional for a comprehensive assessment.
Does BMI differ by age or gender?
The standard adult BMI formula and categories apply to anyone aged 20 and over, regardless of gender. For children and teens (2–19), BMI is interpreted differently using age-and-sex-specific percentile charts. This calculator is designed for adults.
How often should I check my BMI?
Checking your BMI once every few months is enough for general health monitoring. If you're on a weight-management programme, you might check monthly. Remember that BMI is only one indicator — waist circumference, body-fat percentage, and overall fitness matter too.