BMI Calculator
Calculate your body mass index and see the healthy weight range for your height.
For adults 20+ · Based on CDC & WHO guidelines · Updated
Enter your height and weight
Your BMI
Healthy weight for your height: –
Your result and the healthy range for your height will appear here.
Waist-to-height ratio:
If you’re worried about eating or your weight, free and confidential support is available from ANAD.
Under 20? BMI works differently for kids and teens.
Use the Kids & Teens calculator →
Show detailsHide details
- Healthy range
- Calculation
- –
- BMI Prime
- –
- Asian cut-offs
- –
Asian BMI calculator →
History cleared.
Before you rely on BMI
- Under 20? Use the Kids & Teens calculator.
- Pregnant? Weight guidance uses your pre-pregnancy BMI.
- Very muscular or an athlete? BMI may overestimate body fat.
- History of an eating disorder? Talk to a healthcare professional before focusing on numbers. Free, confidential support: ANAD.
Next steps: Check your waist-to-height ratioSee the healthy weight for your heightTalk to your doctor if your BMI is outside the healthy range
On this page
What does your BMI mean?
For adults 20 and older, BMI places you in one of these categories. It’s a quick screening tool: it can flag a possible weight-related health risk, but it doesn’t diagnose anything on its own.
| Below 18.5 | Underweight |
|---|---|
| 18.5–24.9 | Healthy weight |
| 25–29.9 | Overweight |
| 30–34.9 | Obesity, class 1 |
|---|---|
| 35–39.9 | Obesity, class 2 |
| 40 and above | Obesity, class 3 |
Lower cut-offs (overweight from 23, obesity from 27.5) are recommended for people of South Asian, Chinese, other Asian, Middle Eastern, Black African or African-Caribbean family background. Asian BMI calculator →
See the full BMI chart by height and weight →
What specific values mean: 18.5 · 23 · 25 · 27 · 30 · 35 · 40
How is BMI calculated?
BMI is your weight divided by your height squared.
- Metric: BMI = weight (kg) ÷ height (m)². Example: 70 ÷ 1.70² = 24.2
- US units: BMI = 703 × weight (lb) ÷ height (in)². Example: 703 × 150 ÷ 67² = 23.5
Healthy weight for your height
A healthy BMI (18.5–24.9) corresponds to a weight range that depends on your height.
BMI for children and teens
For ages 2 to 19, BMI is compared with children of the same age and sex using CDC growth charts. The result is a percentile, not an adult category, so the same BMI can mean different things at different ages. A healthy weight runs from the 5th to just below the 85th percentile.
Limitations of BMI
BMI doesn’t separate muscle from fat or show where fat is stored, so it can overestimate body fat in athletes and underestimate it in older adults who have lost muscle. Fat around the middle carries more health risk, so guidelines now pair BMI with a waist measure. The UK’s National Institute for Health and Care Excellence (NICE) advises keeping your waist to less than half your height, a waist-to-height ratio under 0.5. In 2025, a Lancet commission advised against diagnosing obesity from BMI alone.
BMI for women and men
Adult BMI uses the same formula and the same categories for women and men. At the same BMI, women tend to carry more body fat than men, which is one reason a waist measurement is a useful second check. US guidance links higher health risk to a waist above 35 inches (88 cm) for women and 40 inches (102 cm) for men.
Frequently asked questions
What is a healthy BMI for adults?
18.5 to 24.9. With the lower cut-offs recommended for people of South Asian, Chinese, other Asian, Middle Eastern, Black African or African-Caribbean family background, the healthy range is 18.5 to 22.9.
Is BMI accurate?
It measures weight relative to height accurately and works well for screening, but it’s only an indirect estimate of body fat. Pair it with a waist measurement and your clinician’s assessment.
What BMI is considered obese?
A BMI of 30 or higher for most adults, or 27.5 or higher with the lower cut-offs above. Obesity is split into class 1 (30–34.9), class 2 (35–39.9) and class 3 (40 or higher).
Why does my BMI say overweight when I’m muscular?
BMI only sees total weight, and muscle is dense. If you’re very muscular, your waist-to-height ratio or a body-fat measurement will give a better picture.
How often should I check my BMI?
There’s no set rule. BMI usually changes slowly, so occasional checks, or the measurements taken at routine medical visits, are enough for most adults. You can save results on this device to see changes over time.