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BMI Calculator for Men, Women & Kids
Instantly calculate your Body Mass Index (BMI) to check if you're in a healthy weight range. Updated for 2025 with WHO standards.
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Understanding Your BMI Results
Body Mass Index (BMI) is a simple calculation using a person's height and weight. The formula is BMI = kg/m² where kg is a person's weight in kilograms and m² is their height in metres squared. A BMI of 25.0 or more is overweight, while the healthy range is 18.5 to 24.9.
💡 Expert Tip from Sarah Jenkins, RD
Don't stress too much about the exact number. BMI is just a screening tool—it can't tell the difference between muscle and fat. I've worked with athletes who have "high" BMIs but are in amazing shape. Think of this as a starting point, not some final judgment on your health.
Is BMI Accurate for Everyone?
While BMI is useful for the general population, it has limitations. It does not distinguish between weight from fat and weight from muscle. Therefore:
- Athletes: May be classified as overweight due to muscle mass.
- Elderly: May be classified as normal weight but have low muscle mass (sarcopenia).
- Pregnancy: BMI is not applicable during pregnancy.
⚠️ Common Mistake: Weighing at the Wrong Time
Your weight fluctuates throughout the day by up to 2-3 kg (4-6 lbs) due to water retention and food intake. For the most consistent BMI tracking, weigh yourself first thing in the morning, after using the bathroom and before breakfast.
BMI Categories (WHO Standards)
According to the World Health Organization (WHO), the standard weight status categories associated with BMI ranges for adults are:
- Underweight: BMI below 18.5
- Normal weight: BMI 18.5 – 24.9
- Overweight: BMI 25.0 – 29.9
- Obesity: BMI 30.0 and above
References
- Centers for Disease Control and Prevention. About Adult BMI.
- World Health Organization. Obesity and Overweight.
Reviewed by Sarah Jenkins, RD
Registered Dietitian & Sports Nutritionist
Sarah double-checks that everything here is medically accurate and up-to-date.
Frequently Asked Questions
Is BMI accurate for muscular people?
Not really. BMI can't tell the difference between muscle and fat. If you lift weights regularly or you're an athlete, your BMI might say you're "overweight" even if you're lean. In those cases, body fat percentage or waist circumference are better measures.
What's a healthy BMI range?
For adults, a BMI between 18.5 and 24.9 is considered normal weight. Below 18.5 is underweight, 25-29.9 is overweight, and 30+ is classified as obese. But remember, these are just guidelines—individual health varies.
Should I use BMI to track weight loss?
It's okay as a rough guide, but don't obsess over it. Track your BMI monthly, not daily. Better yet, combine it with how your clothes fit, energy levels, and strength improvements. The scale doesn't tell the whole story.