KokoroFlow calculator
Use US units to estimate BMI from height and weight.
Use US units: feet, inches, and pounds.
Body Mass Index is a simple estimate based on height and weight. It can be useful as a broad screening number, but it does not measure body composition, muscle, age, or health conditions.
BMI = weight in pounds ÷ height in inches squared × 703.
For personal medical questions, use a qualified health professional.
Body Mass Index estimates body fat using only two numbers — height and weight — so it's fast to calculate but blind to what actually makes up your weight. Two people at the same height and weight can have very different body compositions: one might carry more muscle, the other more fat, and BMI cannot tell them apart. That's why it's best used as a broad screening number, not a diagnosis. Clinicians typically pair it with other measures — waist circumference, activity level, family history — before drawing conclusions about health.
| Category | BMI range |
|---|---|
| Underweight | Below 18.5 |
| Normal range | 18.5 – 24.9 |
| Overweight | 25.0 – 29.9 |
| Obese | 30.0 and above |
An adult who is 5'8" (68 inches) and weighs 160 lb: BMI = 160 ÷ (68 × 68) × 703 = 24.3 — inside the normal range, close to the upper edge. At that same height, the normal-range window (18.5–24.9) spans roughly 122–164 lb, so a change of a few pounds near the edges can shift the category, which is one reason BMI is treated as a screening estimate rather than a precise health verdict.
Not reliably. Muscle is denser than fat, so a muscular, low-body-fat person can score "overweight" on BMI despite having a lean physique. BMI does not distinguish muscle mass from fat mass, which is its best-known limitation.
The standard adult BMI scale (18.5–24.9 as "normal") is the same reference range for adult men and women. It is not adjusted for age within adulthood, though body composition naturally shifts with age — which is part of why doctors weigh BMI alongside other factors rather than using it alone.
It doesn't measure body fat percentage, fat distribution (e.g. waist-to-hip ratio), muscle mass, bone density, or ethnicity-specific risk differences. Waist circumference and body composition testing are common complements when a fuller picture is needed.
No — this calculator uses the adult BMI formula and adult category thresholds. Children and teens are assessed against age- and sex-specific growth percentiles instead, which a pediatrician or a dedicated pediatric BMI tool should be used for.
Treat it as a starting point for a conversation, not an endpoint. If your result concerns you, or you want a more complete picture, a qualified health professional can interpret it alongside your full history.