BMI Calculator
Calculate Body Mass Index with a visual scale, healthy weight range, and BMI categories.
Your BMI
24.4
NormalHealthy weight range for your height
129 - 174 lbs
BMI is a general screening tool and not a diagnostic measure. It does not account for muscle mass, bone density, age, sex, or ethnicity. Athletes and muscular individuals may have a high BMI despite being healthy. Consult a healthcare professional for personalized health assessment.
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BMI Categories and What They Mean
| BMI Range | Category | Health Risk |
|---|---|---|
| Below 18.5 | Underweight | Increased risk of nutritional deficiency, osteoporosis |
| 18.5–24.9 | Normal weight | Lowest risk for weight-related health conditions |
| 25.0–29.9 | Overweight | Elevated risk for cardiovascular disease, type 2 diabetes |
| 30.0–34.9 | Obesity Class I | High risk for multiple chronic conditions |
| 35.0–39.9 | Obesity Class II | Very high risk |
| 40+ | Obesity Class III | Extremely high risk |
BMI Limitations
BMI doesn't distinguish muscle from fat. A highly muscular person (bodybuilder, athlete) may have an "overweight" or "obese" BMI while having very low body fat. Conversely, someone with a "normal" BMI can have high body fat and low muscle (called "normal weight obesity").
BMI also doesn't account for fat distribution — abdominal fat carries higher health risk than fat stored elsewhere. Use our body fat calculator for a more detailed estimate. BMI is a screening tool, not a diagnostic one. Always consult a healthcare provider for medical advice.
BMI vs. Other Measures
For a more comprehensive picture of your body composition, consider using our body fat calculator which compares a legacy Hodgdon–Beckett circumference equation with a BMI-based screening formula. Our ideal weight calculator compares multiple medical formulas (Devine, Robinson, Miller, Hamwi) to give you a range of estimates.
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How this is calculated
Body mass index (BMI) compares weight with height. The calculator converts to metric first, then applies the standard formula and category bands.
Formulas
BMI is weight in kilograms divided by height in meters squared, rounded to one decimal.
BMI = kg ÷ m²
With pounds and inches the same value is:
BMI = lb ÷ in² × 703
The categories use the bands in the NHLBI guidelines, with the obesity classes the guidelines define.
under 18.5 · 18.5–24.9 · 25.0–29.9 · class I 30.0–34.9 · class II 35.0–39.9 · class III 40 and above
The weight range shown as healthy is the weight at BMI 18.5 to 24.9 for your height.
weight = BMI × m²
Sources
- NHLBI, Clinical Guidelines on the Identification, Evaluation, and Treatment of Overweight and Obesity in Adults. Gives the BMI formula in kg/m² and in pounds and inches (× 703), and the weight classification table by BMI.
- NHLBI, Calculate Your BMI. Lists the underweight, healthy, overweight and obesity ranges.
How we test this
This tool is checked against independent formulas every time the site is released, and a release does not ship if a check fails. Example from the test suite: 70 kg at 1.75 m gives BMI 22.9, Normal. The test divides 70 by 1.75² itself and checks the calculator and its category agree.
The test is “bmi: 70 kg at 1.75 m is 22.9 (Normal)” in tests/golden-calculators.test.mjs. More on how all tools are tested: our testing approach.
Assumptions and limits
- BMI does not separate fat from muscle, so it can overstate body fat in muscular people and understate it in older adults who have lost muscle.
- The bands are for adults. Children and teenagers use age- and sex-specific percentiles that this calculator does not provide.
- An estimate for general information, not medical advice. Talk to a health professional about your own situation.
Last reviewed , the date of the latest change to this tool's calculation or content.
Navigation
When to use this
You step on a scale at the doctor's office and hear the number, but a number without context is meaningless. BMI exists to give that weight a rough frame of reference — it compares your weight to your height and places the result on a standardized scale used by clinicians worldwide. If you are curious where you fall on that scale before an appointment, or tracking changes over months of lifestyle adjustments, this calculator gives you an instant answer in both imperial and metric units.
BMI is also commonly requested on health insurance applications, military and law enforcement fitness screenings, and certain employment physicals. If a form asks for your BMI and you do not have it memorized, plug in your height and weight here and you will have it in seconds. It is faster than doing the math manually (weight in kg divided by height in meters squared) and eliminates unit-conversion errors.
That said, BMI is a population-level screening tool, not a diagnosis. It cannot distinguish between muscle and fat, does not account for bone density, and was originally designed using data from European populations. A bodybuilder and a sedentary person of the same height and weight will get the same BMI. If your result surprises you — in either direction — talk to a healthcare provider who can assess body composition, waist circumference, blood markers, and the full picture that a single number cannot capture.
Good to know
The formula is simple but the interpretation is not. BMI equals weight in kilograms divided by height in meters squared (kg/m²). The math is straightforward, but the WHO category boundaries — 18.5, 25, 30 — are statistical thresholds, not cliff edges. A BMI of 24.9 and 25.1 are clinically almost identical, even though they fall in different categories.
Athletes routinely score "overweight" or "obese." Muscle is denser than fat. Rugby players, powerlifters, and even recreational CrossFitters often have BMIs above 25 while carrying very little body fat. If you train with weights regularly, BMI alone is not a useful health metric for you — consider a body fat percentage measurement instead.
BMI underestimates risk in some groups. Research shows that people of South Asian descent may face elevated metabolic risk at BMIs below 25, leading some health organizations to use lower thresholds for those populations. Age also matters — older adults tend to lose muscle mass, so a "normal" BMI may mask a higher body fat percentage.
Children and teens use a different system. Pediatric BMI is expressed as a percentile relative to age and sex rather than the fixed adult categories. This calculator uses the adult formula, so it is not appropriate for anyone under 18.
It is one data point, not a verdict. BMI correlates with health outcomes at a population level, but individual health depends on dozens of factors: blood pressure, cholesterol, blood sugar, fitness level, sleep, stress, and genetics. Use BMI as a starting point for a conversation with your doctor, not as the final word.
Quick Reference
| BMI Range | WHO Category | Notes |
|---|---|---|
| Below 16.0 | Severe Underweight | Medical attention recommended |
| 16.0 – 16.9 | Moderate Underweight | May indicate nutritional deficiency |
| 17.0 – 18.4 | Mild Underweight | Monitor trends over time |
| 18.5 – 24.9 | Normal Weight | Statistically lowest health risk |
| 25.0 – 29.9 | Overweight | Risk depends on other factors |
| 30.0 – 34.9 | Obese Class I | Increased metabolic risk |
| 35.0 – 39.9 | Obese Class II | Significantly increased risk |
| 40.0 and above | Obese Class III | Highest risk category |