BMI Calculator
Calculate your Body Mass Index (BMI) from height and weight in metric or imperial units.
Your BMI
24.2
BMI
24.22
Normal weight
Category range
18.5 – 24.9
What Is BMI and How Should You Use It?
Body Mass Index (BMI) is a number from your height and weight that gives a quick screening of whether your weight is in a range often linked to health. The formula — weight in kilograms divided by height in metres squared — is used worldwide by public health bodies. It needs no special equipment and at the population level relates reasonably well to body fat.
Common BMI bands are: underweight (below 18.5), normal (18.5–24.9), overweight (25.0–29.9), and obese (30.0 and above). People outside the normal band have, on average, higher risks of some diseases — but these are group-level trends, not personal diagnoses. BMI cannot tell muscle from fat, bone density, or where fat is stored (visceral fat matters more than subcutaneous fat).
Treat BMI as a starting point. If yours is outside the healthy range, discuss it with a clinician; they may use waist size, body composition, or blood tests. Together with fitness, diet, blood pressure, and glucose, BMI is one part of the picture — sustainable habits matter more than any single number.
BMI is a screening index, not a diagnosis—muscle mass, bone density, and fat distribution vary widely. Athletes may read “overweight” while metabolically healthy.
Pair with the TDEE calculator when moving from screening to rough calorie planning; the unit converter helps swap kg/lb without rework.
Related tools
These free tools pair well with this page — open them in a new tab to finish your workflow.
Frequently Asked Questions
What is BMI?
Body Mass Index (BMI) is a number derived from your height and weight. The formula is weight(kg) / height(m)². It is widely used as a screening tool to identify potential weight-related health issues in adults.
What are the BMI categories?
The standard WHO categories are: Underweight (< 18.5), Normal weight (18.5–24.9), Overweight (25–29.9), and Obese (≥ 30). Obesity is further split into Class I (30–34.9), Class II (35–39.9), and Class III (≥ 40).
Is BMI accurate for everyone?
BMI is a useful population-level screening tool, but it has limitations. It does not account for muscle mass, age, sex, or ethnic differences. Athletes often have a high BMI despite low body fat. Consult a healthcare professional for a complete assessment.
How is imperial BMI calculated?
Using pounds and inches: BMI = 703 × weight(lb) / height(in)². The factor 703 is a unit-conversion constant. For example, a 5′7″ (67 in) person weighing 154 lb: BMI = 703 × 154 / 67² ≈ 24.1.
What BMI is considered healthy?
A BMI between 18.5 and 24.9 is generally considered healthy for most adults. However, for some ethnic groups (e.g. Asian adults) health risks may begin at lower thresholds (around 23). Always consider BMI alongside other health indicators.