Quick facts
- •BMI is weight in kilograms divided by height in metres squared. At 175 cm and 75 kg that is 24.5, which falls in the healthy range.
- •For adults, the standard WHO bands are: under 18.5 underweight, 18.5 to 24.9 healthy weight, 25 to 29.9 overweight, and 30 or above obesity.
- •At 5 ft 8 in (173 cm), the healthy range is about 122 to 164 lb (55 to 74 kg).
- •Some health bodies use lower cut-offs for people of South Asian, Chinese and several other backgrounds, because health risks can appear at a lower BMI. A common pair is 23 for increased risk and 27.5 for high risk.
- •Children and teenagers are not judged on the adult table. They use BMI-for-age percentiles that take age and sex into account.
Quick reference
| BMI | Category | When it can mislead |
|---|---|---|
| Below 18.5 | Underweight | Naturally slim builds, but also low muscle or illness |
| 18.5 to 24.9 | Healthy weight | Older adults who have lost muscle |
| 25.0 to 29.9 | Overweight | Muscular people and athletes |
| 30.0 to 34.9 | Obesity, class 1 | Very muscular people |
| 35.0 to 39.9 | Obesity, class 2 | Rarely misleading |
| 40.0 and above | Obesity, class 3 | Rarely misleading |
Worked examples
I am 5 ft 8 in and 175 lb. What is my BMI?
BMI 26.6, which is in the overweight band
The formula is 175 × 703 ÷ 68² (height in inches). The healthy range for your height is about 122 to 164 lb, so you are about 11 lb above the top of it. Whether that matters depends on your waist size, your fitness and your blood pressure and bloods.
I lift weights four days a week and my BMI says overweight. Should I worry?
Not by itself. Check waist size and body fat too
A 5 ft 10 in person weighing 200 lb has a BMI of 28.7, even with low body fat. A sedentary person at the same size gets the same number. A tape measure around the waist and a body fat estimate show the difference.
What is the healthy weight at 175 cm?
About 57 to 76 kg
Multiply 18.5 and 24.9 by the height in metres squared (1.75 × 1.75 = 3.0625). That gives roughly 56.7 kg and 76.3 kg. At 75 kg the BMI is 24.5.
My 80-year-old mother has a normal BMI. Is that reassuring?
Partly. Ask about muscle, strength and appetite
At that age, losing muscle or losing weight without trying is often a bigger concern than the BMI number. A doctor can check strength, diet and nutrition.
Treating BMI as a verdict on your health
The mistake
Reading one BMI figure as proof that you are healthy or unhealthy.
Do this instead
Use BMI as one input. Add waist circumference, blood pressure, blood sugar, fitness and how you feel. If you are very muscular, ask about body fat percentage.
Why it matters
People can feel needless shame over a number, or be falsely reassured and miss warning signs such as muscle loss or fat around the waist.
Why a bmi calculator matters
A screening number, not a diagnosis
- •BMI is quick, free and easy to compare. That is why doctors use it as a first check.
- •It suggests when other measures, such as waist size, blood pressure or blood tests, are worth looking at.
- •It does not tell you how healthy you are or how you eat, sleep or move.
- •If a result worries you, talk to a doctor instead of relying on one number.
Why athletes can score high
- •BMI uses weight and height only. It cannot tell muscle from fat.
- •People who lift weights or play contact sports can land in the overweight band with a low body fat percentage.
- •Waist measurement and body fat percentage give a clearer picture for them.
- •If you train regularly, treat the result as a prompt to measure something else.
What changes after 65
- •Muscle tends to decline with age, even when weight stays the same.
- •A healthy-looking BMI can sit alongside low muscle mass and low strength.
- •Grip strength, walking speed and recent unplanned weight loss tell doctors more at that stage.
- •For older adults, a slightly higher BMI is not always a concern, so ask your doctor what is right for you.
What makes this bmi calculator useful
Metric and imperial
Enter kilograms and centimetres, or pounds and feet and inches. The result and the healthy range follow whichever you choose.
Healthy range for your height
You see a weight range in your own units, not just a category label.
Athlete and age notes
Short notes explain when the number can be misleading, including for people who train and for adults over 65.
Printable summary
A clean summary with the limits stated, which you can take to an appointment.
Professional applications
Primary care
Doctors use BMI as a quick first check and then look at waist size, blood pressure, blood sugar and family history.
A BMI of 31 leads to a conversation and further tests, not a diagnosis on its own.
Public health
Researchers use BMI because it is easy to collect from large groups and compare across countries and years.
It is well suited to tracking trends in a population, and less suited to judging one person.
Fitness coaching
Coaches pair BMI with waist circumference, strength and body fat rather than relying on it alone.
A client whose BMI barely moved but whose waist dropped 3 inches is making progress that the scale does not show.
Historical context
Frequently asked questions
How is BMI calculated?+
In metric units, divide weight in kilograms by height in metres squared. In imperial units, multiply weight in pounds by 703 and divide by height in inches squared. For example, 175 lb at 68 inches gives 175 × 703 ÷ 4,624 = 26.6.
What is a good BMI for an adult?+
For most adults, 18.5 to 24.9 is classed as a healthy weight. Some groups, including people of South Asian and Chinese background, may have higher health risk at lower BMIs, so ask your doctor which range applies to you.
Is BMI accurate for athletes and older adults?+
It is less reliable for both. Muscular people can read high with low body fat. Older adults can read normal while losing muscle. Body composition tests such as DEXA scans or skinfold measurements are more informative.
Can I use this BMI calculator for children?+
No. Under 18, BMI is compared with percentiles for the child’s age and sex, such as the CDC growth charts. The adult categories do not apply, so ask a paediatrician or school nurse.
What this calculator cannot do+
It cannot measure body fat, muscle, bone density or where fat is stored. It does not adjust for ethnicity, pregnancy or medical conditions, and it cannot diagnose anything. Use it as one data point and talk to a healthcare professional about your results.