BMI Calculator — Body Mass Index & Healthy Weight Range | Magic Ai Calculator

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Everyday Tools — Health & Fitness

— BMI Enter height & weight

BMI Calculator: check your Body Mass Index in seconds.

Enter your height and weight, in metric or imperial units, and instantly see your BMI, your category, and the healthy weight range for your height — no manual math needed.

Enter your details

The gauge on the right updates instantly.

1. Units
2. Height & weight
3. BMI categories (adults 20+)
Underweight< 18.5
Normal18.5 – 24.9
Overweight25 – 29.9
Obese30 +
Formula

Metric: BMI = weight (kg) ÷ height² (m²). Imperial: BMI = [weight (lb) ÷ height² (in²)] × 703. Both give the same result for the same body.

Categories

Adult BMI is grouped into underweight, normal, overweight, and obese. These ranges apply to adults 20 and older, regardless of age or sex.

A starting point, not a diagnosis

BMI doesn’t separate fat from muscle or bone. Use it as a screening signal, and talk to a healthcare provider about what your number means for you.

This calculator is for general informational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

About

Understanding your Body Mass Index

Maintaining a healthy lifestyle starts with understanding your body, and Body Mass Index is one of the easiest starting points — fast to calculate and useful for anyone who wants to stay informed about their health, whether the goal is losing weight, building muscle, or simply tracking progress.

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What is BMI?

Body Mass Index is a numerical value calculated from your height and weight. Doctors, fitness professionals, and health organizations use it to sort people into weight groups — underweight, normal weight, overweight, or obese.

BMI doesn’t measure body fat directly, but it’s a reliable indicator of whether your weight sits within a healthy range for your height.

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How the calculator works

  • Enter your height — in centimeters or feet and inches.
  • Enter your weight — in kilograms or pounds.
  • Get an instant result — your BMI value plus the category it falls into, shown on the gauge above.

The same formula works for both men and women; only how the result is interpreted may shift slightly with age, muscle mass, and activity level.

Healthy tips based on your BMI category

Underweight

Focus on nutrient-rich foods and strength training to build healthy mass.

Normal weight

Maintain a balanced diet and stay consistent with regular exercise.

Overweight

Increase physical activity gradually and keep an eye on calorie intake.

Obese

Seek professional guidance for a diet and lifestyle plan that fits you.

BMI is a useful screening tool, but it has limits — athletes can read high due to muscle mass, older adults can carry more body fat at a “normal” BMI, and it doesn’t show where on the body that weight sits. Treat it as a general guideline rather than a diagnosis.

Reference categories via the CDC’s guide to Body Mass Index.

FAQs

Common questions

Is BMI accurate for everyone?+
Not perfectly. Athletes can score high on BMI purely from muscle mass, while older adults can have a “normal” BMI but a higher body fat percentage. BMI also can’t show where on the body fat is carried, so it works best as a general screening guide rather than a precise health measurement.
Is the BMI formula the same for men and women?+
Yes, the calculation itself is identical for adult men and women. What can differ is how a given BMI is interpreted, since factors like muscle mass and activity level vary between individuals.
Does BMI work the same way for children as for adults?+
No. For adults 20 and older, standard BMI categories apply regardless of age or sex. For children and teens, BMI is compared against a percentile chart for their age and sex rather than the fixed adult ranges, so a child’s result should be read differently from an adult’s.
What counts as a healthy BMI?+
For most adults, a BMI between 18.5 and 24.9 falls in the normal weight range. Below 18.5 is considered underweight, 25–29.9 is overweight, and 30 or above is classed as obese.
Can a high or low BMI affect my health?+
A consistently high BMI is associated with a greater risk of conditions like high blood pressure, high cholesterol, and type 2 diabetes, while a very low BMI can point to nutritional deficiencies. Either way, it’s worth discussing your result with a healthcare provider rather than reacting to the number alone.
Should I use BMI alone to judge my health?+
No — BMI is best used as one screening signal among several. Your medical history, activity levels, and other health measurements all matter too, so treat your BMI result as a starting point for a conversation with a healthcare provider, not a final verdict.