What is a healthy BMI?
For most adults, a healthy BMI falls between 18.5 and 24.9. Body mass index is weight in kilograms divided by height in meters squared. It is a quick screening number, not a full health assessment, and the calculator below can show where you land in common adult categories.
How to read the BMI categories
Common adult categories used by WHO are:
| BMI | Category |
|---|---|
| Below 18.5 | Underweight |
| 18.5–24.9 | Healthy / normal weight |
| 25.0–29.9 | Overweight |
| 30.0 and above | Obesity (further classes may apply) |
Read the table as labels for a screening number, not as a diagnosis. If your result sits in the healthy band, that only means the index matched that band, not that every other health marker is fine. If it sits outside the band, that is a prompt to look closer with a clinician, not a verdict by itself.
Edges matter: 18.5 and 25.0 are the usual cutoffs between underweight, healthy, and overweight in this scheme. A BMI of 24.9 and a BMI of 25.0 differ by only 0.1 on the index, yet they land in different labels. That is another reason not to treat the boundary as a cliff.
These bands are population tools. A WHO expert consultation (Lancet 2004; 363:157-63) kept the international BMI cut-offs and identified additional public-health action points (23.0, 27.5, 32.5, and 37.5) for Asian populations. Those action points are for public-health discussion, not a second set of personal targets on this page. Ask a clinician which cut-offs apply to you. This page does not set targets or give personal advice.
WHO’s obesity and overweight fact sheet defines overweight as BMI ≥ 25 and obesity as BMI ≥ 30 for adults. The fuller underweight / normal / overweight / obesity bands in the table above follow WHO’s adult BMI classification used in its nutrition landscape materials.
Children and teens are a different system: WHO and other agencies use age- and sex-specific BMI-for-age charts, not the adult cutoffs on this page. If you are looking up a child’s number, stop here and use a pediatric source instead.
Formula and method
BMI = weight_kg / (height_m × height_m)
Example conversions:
- 5 ft 7 in ≈ 170 cm = 1.70 m
- 154 lb ≈ 70 kg
The on-page tool can take metric or imperial inputs; the worked numbers below use the metric path in the calculator. Convert first if you are working by hand: centimeters to meters (divide by 100), pounds to kilograms (multiply by about 0.4536). Wrong units are the most common way people get a nonsense BMI.
Worked examples
Example A: 170 cm and 70 kg:
Someone who weighs 70 kg and is 1.70 m (170 cm) tall has BMI ≈ 24.2 (Normal).
That is BMI 24.2, category normal.
Example B: same height, 82 kg:
Someone who weighs 82 kg and is 1.70 m (170 cm) tall has BMI ≈ 28.4 (Overweight).
BMI 28.4, category overweight.
Example C: 175 cm and 72 kg:
| Input | Value |
|---|---|
| Height | 175 cm (1.75 m) |
| Weight | 72 kg |
| BMI | 23.5 |
| Category | normal |
That third row uses the same calculator with different height and weight inputs. Use it to see how a small height change shifts the index even when weight barely moves.
Where BMI can mislead
BMI is weight relative to height. It does not measure body fat, muscle, bone, or where weight sits on the frame. Two people with the same BMI can have very different body composition. Muscular people can land in a higher BMI category without high body fat. Treat the number as one screening input, then ask a clinician what else to measure.
Check your BMI
Enter your height and weight to see the number and category instantly. Nothing is sent to a server.
How to read the result
- Pair BMI with other information your clinician uses, never with a single weigh-in as the whole story.
- If the category surprises you, ask what else should be measured rather than chasing the index by itself.
- Children and teens need age- and sex-specific charts; adult cutoffs on this page are not for them.
Related reading
Open the full BMI calculator anytime.
Frequently asked questions
What BMI is considered healthy for adults?
For many adults, a BMI between 18.5 and 24.9 is labeled healthy or normal weight under common WHO-style categories. Individual health still depends on muscle, age, and medical context.
How do you calculate BMI?
BMI = weight (kg) ÷ height (m)². In imperial units, convert pounds and inches to metric first, or use a calculator that handles both.
Is BMI accurate for athletes?
BMI does not separate fat from muscle, so muscular people can score higher without excess fat. Treat BMI as a screening number, not a diagnosis.
Should children use the same BMI ranges?
No. Children and teens need age- and sex-specific BMI percentiles. Adult cutoffs do not apply.
Is this medical advice?
No. Numbrixiya calculators are educational estimates. Talk with a qualified clinician about your health.