BMI Calculator

BMI Calculator: Understanding Your Body Mass Index

Body Mass Index (BMI) is a widely used screening tool that estimates body fat based on your height and weight. While not a direct measure of body fat, BMI provides a quick assessment of whether your weight falls within a healthy range for your height. Our calculator supports both metric (kg/cm) and imperial (lbs/feet) units, displays your BMI category on a visual scale, shows your healthy weight range, and calculates your ideal weight for optimal health.

We include both WHO standard classifications and Asian BMI scales, recognizing that health risks occur at different BMI thresholds for different populations. Premium users can track their BMI over time with our progress tracking feature, helping monitor weight management journeys. For related health calculations, see our Calorie Calculator and Percentage Calculator.

The BMI Formula and Categories

BMI Formula: BMI = Weight (kg) ÷ Height (m)². For imperial units: BMI = (Weight (lbs) × 703) ÷ Height (inches)². A person weighing 70 kg at 175 cm height has a BMI of 70 ÷ 1.75² = 22.9, which falls in the "Normal" category.

WHO Standard Categories: Underweight (<18.5), Normal (18.5-24.9), Overweight (25-29.9), Obese Class I (30-34.9), Obese Class II (35-39.9), Obese Class III (≥40). These thresholds are based on statistical associations with health risks across diverse populations.

Asian BMI Scale: Research shows that Asian populations experience higher health risks at lower BMI levels. The Asian BMI scale uses modified thresholds: Normal (18.5-22.9), Overweight (23-24.9), Obese Class I (25-29.9), Obese Class II (≥30). Our calculator lets you switch between scales based on your background.

BMI Limitations and When It Falls Short

Athletes and muscle mass: BMI doesn't distinguish between muscle and fat. A muscular athlete may have a "overweight" BMI while having very low body fat. Similarly, elderly individuals may have normal BMI but unhealthy body composition due to muscle loss (sarcopenia).

Age and gender: Women naturally carry more body fat than men, and body composition changes with age. BMI uses the same thresholds regardless, which may over- or underestimate health risks for certain demographics.

Fat distribution matters: Where you carry fat affects health risk more than total fat. Abdominal (visceral) fat is more dangerous than subcutaneous fat. Someone with normal BMI but high waist circumference may face elevated health risks. Consider measuring waist-to-hip ratio alongside BMI. Plan your finances with our Savings Calculator.

Not for children: Child and adolescent BMI uses age- and gender-specific percentiles rather than fixed thresholds. Our calculator is designed for adults 18+. Pediatric BMI assessment requires different tools.

Healthy Weight Ranges and What They Mean

Our calculator shows your healthy weight range—the weight range where your BMI would fall between 18.5 and 25 (or 18.5-23 for Asian scale). This gives you a realistic target rather than a single number, acknowledging that healthy weight varies.

The ideal weight (BMI of 22) represents the midpoint of the healthy range, often associated with the lowest health risks statistically. However, your personal ideal may differ based on body composition, fitness level, and individual health factors. Consult healthcare providers for personalized guidance.

Weight change recommendations appear when your BMI falls outside the healthy range, showing approximately how much weight to lose or gain. These are estimates for reference—actual weight management should involve healthcare professionals and consider individual circumstances. Calculate discounts on gym memberships with our Discount Calculator.

Using BMI for Health Decisions

BMI as one data point: BMI should be considered alongside other health metrics: blood pressure, cholesterol, blood sugar, physical activity level, diet quality, and family history. A "normal" BMI doesn't guarantee good health, and an "overweight" BMI doesn't necessarily indicate poor health.

Track trends, not single readings: A single BMI measurement is less meaningful than tracking changes over time. Our premium progress tracking lets you record measurements and visualize trends, which is more useful for monitoring weight management efforts.

Frequently Asked Questions

What is a healthy BMI?

By WHO standards, a BMI between 18.5 and 24.9 is considered normal/healthy. For Asian populations, 18.5-22.9 is considered normal due to different body composition characteristics. These ranges are associated with the lowest statistical health risks.

Why does my BMI seem wrong for my body?

BMI is a population-level statistical tool, not a precise individual measure. If you're very muscular, tall, short, or have unusual body proportions, BMI may misclassify you. Consider additional measures like body fat percentage, waist circumference, or consult a healthcare provider for comprehensive assessment. Use our Markup Calculator for financial calculations.

Should I use WHO or Asian BMI scale?

If you're of Asian descent (East Asian, South Asian, Southeast Asian), the Asian scale may better reflect your health risks. Research shows these populations develop metabolic conditions at lower BMI levels. However, consult your healthcare provider for guidance specific to your situation.

How often should I calculate my BMI?

For weight management, weekly or bi-weekly weight checks are sufficient—more frequent checking can be counterproductive due to normal daily fluctuations. Record your BMI monthly for meaningful trend data. Premium users can use our history feature to track progress over time.