BMI Calculator
Body Mass Index (BMI) is a simple screening measure for body fat based on height and weight. Enter your measurements to see your BMI, which category you fall into, and the healthy weight range for your height.
Body Mass Index (BMI) is a number derived from your height and weight that's used as a quick population-level screen for underweight, healthy weight, overweight, and obesity. The CDC and WHO both publish BMI category cutoffs that have been used for decades in clinical and public-health settings.
This calculator uses the standard adult BMI formula. Enter height and weight (imperial or metric) and you'll see your BMI value, the category it falls into, and the healthy-weight range for your height. The math is simple, but the interpretation is where most people get into trouble.
BMI is a screening tool, not a diagnostic one. It treats a 200-pound bodybuilder and a 200-pound sedentary office worker of the same height as identical, even though their actual health profiles are very different. It also doesn't account for sex, age, ethnicity, or where fat is distributed on the body — and waist circumference, body fat percentage, and metabolic markers (blood pressure, cholesterol, fasting glucose) tell a much more complete story.
Inputs
Results
Your BMI
24.4
Category
Normal
Healthy Range
129 - 174 lbs
BMI Categories
Formula
How to use this calculator
- Choose imperial or metric units using the toggle.
- Enter your height. For imperial, use whole feet and inches; for metric, use centimeters.
- Enter your weight. For imperial, use pounds; for metric, use kilograms.
- Read the BMI value and the category. The healthy-weight range shown is the weight range corresponding to BMI 18.5–24.9 at your height.
- Use this as a starting point for a conversation with a clinician, not as a final verdict on your health. A normal BMI does not guarantee good metabolic health, and an elevated BMI does not always indicate a problem (especially for muscular adults).
Worked examples
Average adult
Height: 5'8" (173 cm) Weight: 165 lb (75 kg) BMI: (165 / 68²) × 703 ≈ 25.1 Category: Overweight (just barely — 1 lb less puts this person in Normal) Most healthy-range targets cluster between BMI 20–24, which for this height translates to roughly 131–157 lb.
Muscular athlete
Height: 6'0" (183 cm) Weight: 215 lb (97.5 kg), low body fat BMI: (215 / 72²) × 703 ≈ 29.2 Category: Overweight per BMI But with body fat below 15%, this person has very low metabolic risk. BMI flags them as overweight because the formula can't see muscle vs fat. Use body composition or waist measurement for context.
Healthy-range target
For a person 5'5" (165 cm), the BMI 18.5–24.9 range corresponds to roughly: Lower bound: 111 lb (50.5 kg) Upper bound: 150 lb (68 kg) A 25-pound move within or out of this range tends to be the difference between BMI categories at this height. For larger frames it can take less.
When to use this calculator
Use BMI for a quick gut-check of where you fall on a standard population scale, especially if you've gained or lost meaningful weight and want to know whether you've crossed a clinical category boundary. It's a useful conversation starter with a doctor and a reasonable filter for population studies.
Don't use BMI alone to: - Diagnose obesity in a single individual (especially athletes or older adults with sarcopenia) - Set weight loss goals (waist circumference and body fat percentage are usually more relevant) - Evaluate children or adolescents (BMI-for-age percentiles are the right tool — different from adult cutoffs) - Compare across ethnicities directly (research suggests Asian populations face elevated metabolic risk at lower BMIs, and Black/African populations may carry more muscle mass at the same BMI)
A complementary metric is waist-to-height ratio (waist ≤ half your height is a common simple cutoff). For body composition, DEXA scans, hydrostatic weighing, and BodPod are the gold standards; bioelectrical impedance scales are convenient but noisy.
Common mistakes to avoid
- Treating BMI as a diagnosis instead of a screen. A "high" BMI is a flag to look closer, not a verdict.
- Using adult BMI cutoffs for children. Children use BMI-for-age percentiles from the CDC growth charts, which adjust for age and sex.
- Forgetting that BMI doesn't distinguish muscle from fat. Athletes routinely score in the "overweight" range with very low health risk.
- Mixing units. Plugging pounds into the metric formula (or kg into imperial) gives nonsense. Use one system consistently.
- Comparing your BMI to social-media targets. Many influencer "ideal" BMIs are in the underweight range, which is associated with worse outcomes than mildly overweight.
- Ignoring fat distribution. Two people with the same BMI but different waist sizes have meaningfully different metabolic risk. Central (abdominal) fat is the higher-risk pattern.
Frequently Asked Questions
Sources & further reading
- About Body Mass Index (BMI) — U.S. Centers for Disease Control and Prevention
- A healthy lifestyle — WHO recommendations — World Health Organization
- Clinical Guidelines on the Identification, Evaluation, and Treatment of Overweight and Obesity in Adults — U.S. National Heart, Lung, and Blood Institute