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Nutrition basics
Learn how balanced eating supports a healthy weight and better well-being.
Nutrition basics guideWhat Is BMI? Learn How BMI Works
BMI, or Body Mass Index, is a simple number that uses your height and weight to estimate whether your weight is in a healthy range for adults. It is a quick screening measure and a starting point — not a medical diagnosis.
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How BMI is calculated: the BMI formula
The BMI formula divides your weight by your height squared (BMI = weight ÷ height²), using kilograms and meters. You can enter metric or imperial units — feet, inches, and pounds — and the free BMI calculator does the math for you. Because BMI only uses height and weight, it has limitations and works best when read alongside other information about your health.
Explore key topics
Move more
Discover simple ways to add more movement to your day and stay active.
Move more guide
Sleep and recovery
Find out how quality sleep helps your body recover and supports a healthy weight.
Sleep and recovery guide
Healthy habits
Build daily habits that support your mind, body, and long-term health.
Healthy habits guide
BMI vs body fat percentage
Compare what BMI and body fat percentage each show — and where they fall short.
BMI vs body fat guide
Healthy recipes
Simple breakfast, lunch, dinner and tea ideas that support a balanced eating routine.
Healthy recipes guide
BMI formula
Worked metric and imperial examples showing exactly how BMI is calculated.
BMI formula guide
BMI limitations
Why BMI can read differently for athletes, older adults, and different body compositions.
BMI limitations guide
Healthy weight range
See the adult healthy-weight range in kilograms or pounds for your own height.
Healthy weight range guide
What your result means
Read your personal BMI category and result with the right context.
Result meaning guideHealthy habits that support a better BMI
Eat well
Focus on whole foods, vegetables, lean proteins, whole grains, and healthy fats.
Stay active
Aim for regular movement throughout the week—walking, cardio, or strength training.
Sleep enough
Aim for 7–9 hours of quality sleep each night to support recovery and hormone balance.
Stay consistent
Small, consistent actions over time lead to lasting results and better habits.
What affects your BMI?
Body composition
BMI doesn’t distinguish between fat mass and lean mass.
Age
Metabolism and body composition change with age.
Muscle mass
More muscle can lead to a higher BMI, even with low body fat.
Daily activity
Your activity level affects your energy needs and weight management.
Lifestyle factors
Stress, hydration, sleep, and environment all play a role.
BMI is a screening tool, not a full diagnosis. It should be used with other health information and professional guidance.
Understanding BMI limitations
BMI does not measure body fat directly and may be less accurate for athletes, bodybuilders, older adults, pregnant people, and others. It’s one of many tools. Use it to get a general idea, not as the only measure of health.
Small changes that help
Eat balanced meals
Include vegetables, fruits, whole grains, lean proteins, and healthy fats.
Walk more
A short walk each day can boost energy and support weight goals.
Try strength training
Build muscle, improve posture, and support metabolism.
Stay hydrated
Drink water throughout the day to support digestion and energy.
Get professional advice
Speak with a healthcare professional for personalized guidance and support.
Frequently asked questions
Is BMI an accurate measure of body fat?
BMI does not directly measure body fat. It is a screening estimate based on height and weight.
What BMI range is considered healthy?
For most adults, a BMI between 18.5 and 24.9 is commonly considered the healthy BMI range.
Can I have a healthy BMI and still be unhealthy?
Yes. BMI does not show muscle mass, body fat percentage, fat distribution, blood pressure, fitness level, or other health markers.
How can I improve my BMI?
Small habits can help: balanced meals, regular movement, enough sleep, hydration, and professional guidance when needed.
This tool is for adults 18 years and older and is intended for informational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment.
How this content is maintained
T9 BMI Check is an educational resource for adults. BMI is a screening tool, not a medical diagnosis, and the information here is general rather than personalized medical advice. We research our content against trusted public-health sources, work to keep it factually accurate, and review it periodically. For guidance about your own health, please consult a qualified healthcare professional.
References
Last reviewed: 2026-07-17