Body‑Mass Index (BMI) is a quick way to gauge whether your weight is in a healthy range for your height. Enter your stats in our BMI Calculator, then use the chart below to understand what the number means for your health.
What is BMI?
BMI is calculated with a simple formula: weight (kg) ÷ height (m)2. Because it relies on height and weight alone, BMI is easy to measure but can’t differentiate muscle from fat.
BMI Classification Chart
| BMI | Category |
|---|---|
| < 18.5 | Underweight |
| 18.5 – 24.9 | Normal weight |
| 25 – 29.9 | Overweight |
| 30 – 34.9 | Obesity I |
| 35 – 39.9 | Obesity II |
| ≥ 40 | Obesity III |
Health risks by category
- Underweight – potential nutrient deficiency, bone loss.
- Normal weight – lowest overall health risk.
- Overweight – elevated risk of hypertension, pre‑diabetes.
- Obesity (all classes) – increased risk of type 2 diabetes, heart disease, sleep apnea, certain cancers.
Limitations of BMI
BMI doesn’t account for muscle mass, body‑fat distribution, age or ethnicity. An athlete with high muscle can have a “high” BMI while maintaining low body fat. Pair BMI with waist‑to‑height ratio or body‑fat % for a clearer picture.
How to improve your BMI
- Create a slight calorie deficit (or surplus if underweight).
- Combine strength training with cardio.
- Prioritise whole foods rich in fibre and protein.
- Sleep 7–9 hours per night; manage stress.
- Consult a healthcare professional before major lifestyle changes.
FAQ
- Is BMI accurate for athletes?
- Not always. High muscle mass can inflate BMI, categorising athletes as “overweight” even with low body‑fat.
- Does BMI change with age?
- BMI formula is constant, but body composition shifts with age. Older adults may have more fat at the same BMI.
- How often should I check my BMI?
- Every few months is sufficient unless you’re tracking rapid weight changes under medical guidance.