📏 BMI Calculator (Body Mass Index)

Use this BMI calculator to estimate your body mass index and weight category using either imperial or metric units. Enter your height and weight to see where you fall on standard BMI ranges for adults.

BMI results

Enter your height and weight above, choose your preferred unit system, then select Calculate BMI to see your estimated body mass index and weight category.

BMI breakdown for your height and weight

Once you calculate your BMI, this section will show a detailed breakdown of your inputs, unit conversions, and the healthy weight range for your height.

BMI calculator inputs and key terms

Understanding how BMI is calculated and what each input means can help you use this tool more effectively.

• Unit system: Choose imperial (feet, inches, pounds) or metric (centimeters, kilograms). The calculator automatically performs the necessary conversions.
• Height: Your standing height. In imperial mode, you enter feet and additional inches. In metric mode, you enter height in centimeters.
• Weight: Your body weight in pounds or kilograms, depending on the selected unit system.
• Body Mass Index (BMI): A ratio of weight to height used as a screening tool to classify underweight, normal weight, overweight, and obesity in adults.
• Weight category: A label (such as “Normal weight” or “Overweight”) based on your BMI value and standard adult BMI thresholds.
• Healthy weight range: The range of body weights that would correspond to a BMI of 18.5–24.9 for your height. This is often used as a general target range for adults.

BMI is a population-based screening tool. It does not directly measure body fat and does not distinguish between weight from muscle and weight from fat. People with very high muscle mass, certain medical conditions, or unique body types may not fit neatly into standard BMI categories.

Formulas used in the BMI Calculator

This calculator uses the standard adult BMI formula. Internally, all calculations are performed in metric units, even if you choose imperial inputs.

BMI formula (metric)

When height is in meters and weight is in kilograms:
BMI = Weight (kg) ÷ [Height (m)]²

Converting imperial to metric

For imperial inputs, the calculator first converts your height and weight to metric units:
Height (m) = total height in inches × 0.0254
Weight (kg) = Weight (lb) × 0.45359237

You may also see BMI written directly in imperial form:
BMI = 703 × Weight (lb) ÷ [Height (in)]²
This formula is mathematically equivalent to converting to metric and using the standard BMI equation.

Healthy weight range (BMI 18.5–24.9)

To estimate a weight range that corresponds to a “normal” BMI, the calculator uses:
Minimum healthy weight (kg) = 18.5 × [Height (m)]²
Maximum healthy weight (kg) = 24.9 × [Height (m)]²
Results are then shown in kilograms or pounds depending on your selected unit system.

BMI Calculator FAQs

• What is BMI and what does it tell me?
  BMI, or Body Mass Index, is a quick way to compare your weight to your height. It helps classify adults into groups such as underweight, normal weight, overweight, or obesity. It does not directly measure body fat, but it is widely used as a screening tool for weight-related health risks.
• What is a healthy BMI range for adults?
  For most adults, a BMI between 18.5 and 24.9 is often considered a “normal” or healthy range. A BMI below 18.5 is typically classified as underweight, 25–29.9 as overweight, and 30 or higher as obesity. These ranges are general guidelines and may not apply to everyone.
• Is BMI accurate for athletes or very muscular people?
  BMI can be misleading for people with high muscle mass, such as strength athletes. Because muscle is denser than fat, muscular individuals may have a higher BMI even when their body fat level is moderate. In those cases, body fat measurements and professional evaluation are more informative than BMI alone.
• Can I use this BMI calculator for children or teenagers?
  No. Children and teens use age- and sex-specific BMI charts and percentiles, not the adult cutoffs included here. If you have questions about a child’s growth or weight, it’s best to talk with a pediatrician or other qualified healthcare professional.
• Should I aim for the lowest possible BMI in the healthy range?
  Not necessarily. The healthy BMI range is fairly broad, and the best target for you depends on your body type, health history, and goals. Being at the low end of the range is not automatically better than being in the middle. Focus on overall health, sustainable habits, and guidance from your healthcare team.
• How often should I check my BMI?
  For most adults, checking BMI occasionally—such as a few times a year or during major lifestyle changes—is enough. Day-to-day fluctuations are less important than overall trends in your weight, health habits, and how you feel.