BMI Calculator
Body Mass Index from height and weight.
Adult BMI
Healthy weight22.9
kg/m²Introduction
Body Mass Index is an adult screening measure for whether weight falls in a reference range for height. It doesn’t know your muscle mass, so treat it as a starting point — not a verdict. Children and teens need BMI-for-age assessment instead.
What is BMI Calculator?
Body mass index is a screening measure calculated from weight relative to height. It can be useful for population screening and as one health data point, but it does not directly measure body fat or diagnose health conditions.
Definition: BMI Calculator estimates adult body mass index from height and weight.
Formula
BMI = weight (kg) ÷ height (m)²
Calculation steps
Formula. BMI = weight (kg) / height (m)². Imperial inputs are converted to metric first.
Categories. The ranges shown follow the World Health Organization’s adult classification. Different guidance applies to children, pregnant people and some ethnic groups.
Limits. BMI does not distinguish muscle from fat, so it can misclassify athletes as overweight. Pair it with a body-fat estimate for a fuller picture.
Worked example
Example: BMI for a 70 kg person who is 175 cm tall
Inputs: Weight = 70 kg, Height = 175 cm
- Convert height to metres: 175 cm ÷ 100 = 1.75 m
- Square height: 1.75² = 3.0625
- Divide weight by height²: 70 ÷ 3.0625 = 22.9
BMI ≈ 22.9 — within the normal weight range (18.5–24.9).
Use cases
- Checking an adult BMI from a current height and weight
- Tracking a trend alongside other health measures
- Starting a conversation with a healthcare professional when appropriate
Advantages
- Browser-based processing — entered values and selected files are not sent to our servers
- No account required
- Instant results with a clean, readable interface
- Transparent formula shown on this page
Limitations
- Adult BMI categories are not designed for children or adolescents.
- BMI can be less informative for pregnancy, older adults, muscular athletes, and people with atypical body composition.
- BMI is a screening measure, not a diagnosis or an assessment of body fat distribution.
Frequently asked questions
- Is BMI accurate for athletes?
- Not always — muscle weighs more than fat, so muscular people often land in the ‘overweight’ band. Use the body-fat calculator alongside it.
- Does BMI apply to children?
- No. Children use age- and sex-specific BMI percentiles, not the adult 18.5–24.9 range.
Sources & references
Key points
- BMI Calculator is a free, browser-based calculator for body Mass Index from height and weight.
- Formula: BMI = weight (kg) ÷ height (m)²
- Private, browser-only processing
- Private, browser-based processing