BMI Calculator
Body Mass Index (BMI) is a quick screening tool that estimates whether your weight is in a healthy range for your height. Enter your measurements below to get your BMI and healthy weight range.
BMI Categories
| BMI Range | Category | What it means |
|---|---|---|
| Below 18.5 | Underweight | May indicate malnutrition or other health concerns |
| 18.5 – 24.9 | Normal weight | Associated with the lowest health risk in population studies |
| 25.0 – 29.9 | Overweight | Modestly elevated risk for some conditions |
| 30.0 and above | Obese | Associated with higher risk for heart disease, type 2 diabetes, and other conditions |
These categories apply to adults 20 and older. BMI thresholds differ for children, adolescents, and some ethnic groups (see below).
BMI Formula
Imperial: BMI = (weight in lbs × 703) ÷ (height in inches)²
Metric: BMI = weight in kg ÷ (height in meters)²
For example, a person who is 5′9″ (69 inches) and weighs 160 lbs:
BMI = (160 × 703) ÷ (69²) = 112,480 ÷ 4,761 = 23.6 — Normal weight.
Limitations of BMI
BMI is a useful population-level screening tool, but it has well-known limitations for individuals:
- Muscle mass — Athletes and bodybuilders can have a high BMI while carrying very little body fat, because muscle is denser than fat.
- Body fat distribution — Two people with the same BMI can have very different health risks depending on where they carry weight (abdomen vs. hips).
- Age and sex — Older adults tend to carry more fat for a given BMI than younger adults. Women typically carry more fat than men at the same BMI.
- Ethnicity — Asian populations generally have higher health risks at lower BMI thresholds; some health organisations use a cutoff of 23 (rather than 25) for overweight in Asian adults.
- Children — BMI for children (ages 2–19) is interpreted using age- and sex-specific growth chart percentiles, not the fixed adult thresholds above.
BMI is a starting point for a conversation with a healthcare provider, not a diagnosis.
Frequently Asked Questions
What is a healthy BMI?
For adults, a BMI between 18.5 and 24.9 is classified as normal weight. This range is associated with the lowest all-cause mortality in large population studies, though individual health is influenced by many factors beyond BMI.
How do I calculate BMI in pounds and inches?
Multiply your weight in pounds by 703, then divide by your height in inches squared. Our calculator handles this automatically — just enter feet, inches, and pounds in the Imperial tab.
Is a BMI of 25 overweight?
Yes, by standard WHO and CDC definitions, a BMI of 25.0 marks the start of the overweight range. A BMI of 24.9 is the upper limit of normal weight.
Does BMI apply to pregnant women?
No — standard BMI is not used during pregnancy. Weight gain during pregnancy is assessed separately based on pre-pregnancy BMI.
Can I lose weight to reach a healthy BMI?
The healthy weight range displayed above shows you the target weight span for your height. Reaching it through sustained calorie management and exercise is the standard approach; consult a healthcare provider for personalised guidance.
