BMI Calculator
Calculate Body Mass Index and understand your health category
BMI Categories
Underweight
< 18.5
Normal
18.5 – 25
Overweight
25 – 30
Obese
30+
What is it?
BMI (Body Mass Index) is a simple screening measure that estimates whether your weight is healthy for your height. It's widely used by health organizations as a quick, population-level indicator, though it doesn't directly measure body fat.
Formula
BMI = Weight (kg) ÷ Height (m)²
Formula Explanation
The formula divides your weight in kilograms by the square of your height in meters. Squaring the height adjusts for the fact that taller people naturally weigh more, making BMI a reasonable way to compare body weight across people of different heights.
Example Calculation
A person weighing 70 kg with a height of 1.75 m has a BMI of 70 ÷ (1.75 × 1.75) = 22.9, which falls in the Normal weight range.
How to Use
- Enter your weight and select kg or lbs.
- Enter your height in cm, or in feet and inches.
- View your BMI value and category instantly.
Benefits
- Gives a quick, free way to screen for weight-related health risk without special equipment.
- Uses only height and weight, so it can be checked anywhere in seconds.
- Widely recognized by doctors and health organizations, making results easy to discuss with a professional.
Use Cases
- Tracking weight trends over time as part of a fitness or health routine.
- Getting a starting point before a medical checkup or health insurance assessment.
- Screening large groups quickly in clinical or research settings.
What Your Result Means
Your BMI places you into one of four categories — Underweight, Normal, Overweight, or Obese. This is a screening indicator, not a diagnosis: it flags whether your weight-to-height ratio is in a range associated with higher health risk, but factors like muscle mass, age, and body composition also matter.
Tips
- Weigh yourself at the same time of day (e.g. morning, before eating) for consistent tracking.
- Track BMI trends over weeks or months rather than reacting to a single reading.
- Pair BMI with other measures like waist circumference or body fat % for a fuller picture.
Common Mistakes
- Treating a single BMI reading as a medical diagnosis instead of a screening estimate.
- Entering height or weight in the wrong unit (e.g. lbs instead of kg) without switching the selector.
- Ignoring that BMI can overestimate body fat in very muscular people and underestimate it in older adults with low muscle mass.
FAQs
What is a healthy BMI range?
A BMI between 18.5 and 24.9 is generally considered a healthy weight range for most adults.
Does BMI account for muscle mass?
No, BMI doesn't distinguish between muscle and fat, so athletes or very muscular individuals may show a higher BMI despite having low body fat.
Is BMI accurate for everyone?
BMI is a general screening tool and may be less accurate for children, elderly people, pregnant women, and highly muscular individuals — consult a doctor for a full assessment.
How often should I check my BMI?
Checking every few months is enough for most people, since BMI mainly reflects weight trends over time rather than day-to-day changes.
Is BMI different for men and women?
The BMI formula itself is the same for everyone, though women naturally tend to have a higher body fat percentage than men at the same BMI.
Can BMI be used for children?
No, this calculator is for adults. Children and teens need age- and sex-specific BMI percentile charts instead of the fixed adult categories.
What should I do if my BMI is outside the normal range?
Use it as a starting point for a conversation with a doctor or dietitian rather than making major changes based on BMI alone.
Does losing weight always lower BMI?
Yes — since BMI is calculated from current weight and height, any change in weight directly changes your BMI, regardless of whether the loss is fat or muscle.
Why do two people with the same BMI look different?
BMI does not account for body composition, so someone with more muscle and less fat can have the same BMI as someone with less muscle and more fat, yet look and be very different physically.
References
This tool is for educational and informational purposes only. Not medical advice.
Last updated: July 25, 2026