BMI Calculator

Enter Your Height & Weight

Height (cm)

Weight (kg)

0.0

1518.5253040+

Weight Categories

< 18.5

Underweight

18.5 - 24.9

Normal

25 - 29.9

Overweight

30+

Obese

Your Healthy Weight Range (BMI 18.5-24.9)

BMI Chart by Height (Metric)

Weight (kg) at the boundary of each BMI category, for common heights.

Height	Underweight <	Normal	Overweight	Obese ≥

How BMI is Calculated

Metric Formula

BMI = Weight (kg) ÷ [Height (m)]²

Imperial Formula

BMI = 703 × Weight (lbs) ÷ [Height (in)]²

Worked Example (Metric)

A person who is 170 cm (1.70 m) tall and weighs 70 kg:

BMI = 70 ÷ (1.70 × 1.70)
BMI = 70 ÷ 2.89
BMI = 24.2 (Normal weight)

Worked Example (Imperial)

A person who is 5'7" (67 inches) tall and weighs 154 lbs:

BMI = 703 × 154 ÷ (67 × 67)
BMI = 108,262 ÷ 4,489
BMI = 24.1 (Normal weight)

Healthy Weight Range for a Given Height

Rearranging the formula to solve for weight at the boundaries of the normal range (BMI 18.5 and 24.9):

Min healthy weight (kg) = 18.5 × [Height (m)]²
Max healthy weight (kg) = 24.9 × [Height (m)]²

Try These Examples

Click any example to instantly calculate.

170 cm, 70 kg

BMI 24.2 - Normal weight

160 cm, 45 kg

BMI 17.6 - Underweight

175 cm, 85 kg

BMI 27.8 - Overweight

5'7", 154 lbs

BMI 24.1 - Normal weight

5'10", 220 lbs

BMI 31.6 - Obese

Frequently Asked Questions

A BMI between 18.5 and 24.9 is considered a healthy weight range for most adults, according to the World Health Organization and CDC. Below 18.5 is classified as underweight, 25 to 29.9 as overweight, and 30 or above as obese. These ranges are population-level guidelines, not a diagnosis - a doctor considers BMI alongside other factors like muscle mass, waist circumference, and overall health.

No. BMI does not distinguish between muscle and fat, so muscular athletes and bodybuilders are often classified as overweight or obese despite having low body fat. It can also underestimate body fat in older adults who have lost muscle mass. BMI is a useful, quick screening tool for the general population, but it does not account for body composition, fat distribution, sex, ethnicity, or age. For a more complete picture, doctors also look at waist circumference, body fat percentage, and family health history.

Metric: BMI = weight in kilograms divided by height in metres, squared (kg/m²). Imperial: BMI = 703 × weight in pounds, divided by height in inches, squared. For example, a person who is 1.7 m tall and weighs 70 kg has a BMI of 70 ÷ (1.7 × 1.7) = 24.2, which falls in the healthy weight range.

The BMI formula and the standard weight categories (underweight, normal, overweight, obese) are the same for adult men and women - BMI itself does not adjust for sex. However, women naturally tend to carry a higher percentage of body fat than men at the same BMI, because BMI cannot distinguish fat from muscle. This is one of the reasons doctors use BMI as a starting screening tool rather than a final verdict on health.

Not with the same fixed categories used for adults. For children and teens (ages 2 to 19), BMI is calculated the same way but then plotted on age- and sex-specific growth charts, since healthy body fat levels change significantly as children grow. A child's result is expressed as a percentile compared to other children of the same age and sex, not as a fixed number like 'normal' or 'overweight'. This calculator uses the adult BMI categories and is intended for adults 20 and older.

A BMI outside the 18.5-24.9 range is a signal to look closer, not a diagnosis. If your BMI suggests underweight or overweight/obese, consider discussing it with a doctor, who can assess waist circumference, blood pressure, blood sugar, and family history alongside your BMI. Small, sustainable changes to diet and activity levels are generally more effective long-term than dramatic short-term changes. If you are muscular with a high BMI but low body fat, BMI alone likely does not reflect your health status accurately.

BMI Calculator - Understand Your Body Mass Index and What It Means

Body Mass Index (BMI) is the simplest, most widely used screening tool for assessing whether your weight is in a healthy range for your height. Doctors, insurers, and health organizations worldwide - including the WHO and CDC - use the same formula and the same four weight categories. This calculator gives you your exact BMI number, your category, and the specific weight range that would put you in the "normal" category at your current height, in both metric and imperial units.

The formula: BMI = Weight (kg) ÷ Height (m)² · Imperial: BMI = 703 × Weight (lbs) ÷ Height (in)²
Quick example: 170 cm, 70 kg BMI 24.2 (Normal weight)

BMI Categories Explained

Below 18.5 - Underweight: May indicate insufficient nutrition, an underlying health condition, or a naturally lean build. Being significantly underweight is linked to weakened immunity and bone density issues.
18.5 to 24.9 - Normal weight: Associated with the lowest average health risk in most population studies. This is the target range most health guidelines recommend for adults.
25 to 29.9 - Overweight: Associated with a moderately increased risk of conditions like type 2 diabetes and high blood pressure, though individual risk varies a lot based on muscle mass, fat distribution, and lifestyle.
30 and above - Obese: Associated with a further increased risk of cardiovascular disease, diabetes, and other conditions. Obesity itself is sometimes further split into Class 1 (30-34.9), Class 2 (35-39.9), and Class 3 (40+).

Why BMI Has Limits - and Why It's Still Useful

BMI only uses two numbers - height and weight - so it cannot tell the difference between muscle, fat, and bone. A muscular athlete and a sedentary person of the same height and weight will get the identical BMI, even though their body composition and health risks are very different. BMI also does not account for where fat is stored on the body (visceral fat around organs is riskier than fat elsewhere), sex differences in typical body fat percentage, or changes in muscle mass with age.

Despite these limits, BMI remains valuable because it is fast, free, requires no special equipment, and correlates reasonably well with body fat percentage across large populations. It is best used as a first screening step - a signal for whether a closer look (waist circumference, body fat percentage, blood work) is worthwhile - rather than a final verdict on anyone's health.

How to Improve an Out-of-Range BMI

If Underweight

Increase calorie intake with nutrient-dense foods (nuts, avocado, whole grains, lean protein)
Add strength training to build muscle mass, not just fat
Eat more frequently - 5-6 smaller meals if large meals feel difficult
Rule out underlying causes (thyroid issues, digestive conditions) with a doctor if weight loss is unintentional

If Overweight or Obese

Aim for a modest, sustainable calorie deficit rather than an extreme one
Prioritize protein and fiber to stay fuller for longer
Combine cardio with strength training to preserve muscle while losing fat
Track progress over weeks, not days - weight naturally fluctuates daily

How this calculator works, and where the numbers come from

The BMI Calculator applies the standard formula for this calculation to the values you enter and updates the result as you type. The calculation itself happens in your browser, and the page explains the method so you can check any result by hand.

Please note: This tool gives general estimates based on published population formulas. It is not medical advice and does not replace assessment by a doctor, dietitian or other qualified professional.

Sources and further reading

Learn more

Read our guide: What BMI Tells You, and What It Quietly Misses

Last reviewed: October 6, 2026 by the CalcQube Editorial Team. See our editorial policy for how we build and check calculators, or report an error.