BMI Calculator

Calculate BMI with ideal weight, BMI Prime, and personalized health insights

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Unit System

BMI Formula

BMI = weight (kg) / height (m)²

How to Use BMI Calculator

Enter your details

Input your height and weight in metric or imperial units.

Calculate

Click calculate to see your BMI score and category.

Review

See where you fall on the BMI scale with health guidance.

Why Choose AllTools BMI Calculator?

  • ✓ 100% free, no account needed
  • ✓ No data stored or transmitted
  • ✓ Metric and imperial units
  • ✓ BMI category classification
  • ✓ Instant results
  • ✓ Ideal weight range for your height
  • ✓ BMI Prime calculation
  • ✓ Ponderal Index
  • ✓ Age and gender inputs
  • ✓ Health risk level indicator
  • ✓ Weight to lose/gain display

Frequently Asked Questions

What is BMI? ▼
BMI (Body Mass Index) is a measure of body fat based on height and weight. It is used as a screening tool for weight categories.
How is BMI calculated? ▼
BMI is calculated by dividing your weight in kilograms by your height in meters squared (kg/m²).
What is a healthy BMI range? ▼
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 obese.
Is BMI accurate for everyone? ▼
BMI is a useful screening tool but does not account for muscle mass, bone density, or body composition. Consult a healthcare provider for personalized advice.
Is my health data stored? ▼
No. All calculations happen in your browser. Nothing is sent to any server.
Does this work on mobile? ▼
Yes, all AllTools tools are mobile-optimized and work on iOS and Android browsers.
What is my ideal weight? ▼
The tool calculates your ideal weight range based on your height using BMI 18.5-24.9 as the healthy range. It shows the exact kg/lbs you need to reach that range.
What is BMI Prime? ▼
BMI Prime is your BMI divided by 25. A value of 1.0 means you are at the upper limit of normal weight. Below 1.0 is normal, above 1.0 is overweight.
What is Ponderal Index? ▼
Ponderal Index (PI) is similar to BMI but uses height cubed instead of squared, making it more accurate for very tall or very short individuals.
Does age and gender affect BMI interpretation? ▼
Yes, the tool adjusts health risk guidance based on age and gender, as healthy weight ranges can vary across demographics.

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