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FitDiary

BMI calculator for women and men

Work out your body mass index from your height and weight. See what your result means and the healthy weight range for your height. It works for adults aged 18 and over, in kg or lb.

Your height and weight

Units
Height

For adults aged 18 and over. For children and teens, use the CDC child and teen BMI calculator.

Your result

Enter your height and weight to see your BMI.

What is BMI?

BMI (body mass index) is your weight in kilograms divided by your height in metres squared. For adults, the World Health Organization treats a BMI below 18.5 as underweight, 18.5 to 24.9 as a healthy weight, 25 to 29.9 as overweight and 30 or more as obesity. It’s a quick screening number, not a measure of body fat.

Doctors use BMI because it’s quick and needs only a tape measure and a set of scales. It works well for comparing groups of people, and less well for any one person, which is why it’s worth reading the limits further down.

How to calculate BMI

There’s one formula, written two ways. Both give the same result:

  • Metric: BMI = weight (kg) ÷ height (m)²
  • Imperial: BMI = 703 × weight (lb) ÷ height (in)²

The calculator shows your BMI to one decimal place and uses that rounded number for the category, so a result of 24.96 shows as 25.0 and counts as overweight. If you use feet and inches, it works from your exact height in inches.

BMI says nothing about how much to eat. For a daily calorie target from your height, weight, age and activity, use the TDEE calculator.

BMI chart for adults

These are the adult categories. They are the same for women and men, and at every age from 18 upwards.

CategoryBMI
UnderweightBelow 18.5
Healthy weight18.5 to 24.9
Overweight25.0 to 29.9
Obesity (class 1)30.0 to 34.9
Obesity (class 2)35.0 to 39.9
Obesity (class 3)40.0 or more

The cut-offs for overweight (25) and obesity (30) are the World Health Organization’s. The healthy weight range and the three obesity classes follow those listed by the US Centers for Disease Control and Prevention (CDC).

Healthy weight for your height

This table shows the weight range for a BMI of 18.5 to 24.9 at common heights.

HeightHealthy weight (kg)Healthy weight (lb)
150 cm (4 ft 11 in)41.6–5692–124
155 cm (5 ft 1 in)44.4–59.898–132
160 cm (5 ft 3 in)47.4–63.7104–141
165 cm (5 ft 5 in)50.4–67.8111–149
170 cm (5 ft 7 in)53.5–72118–159
175 cm (5 ft 9 in)56.7–76.3125–168
180 cm (5 ft 11 in)59.9–80.7132–178
185 cm (6 ft 1 in)63.3–85.2140–188
190 cm (6 ft 3 in)66.8–89.9147–198

Feet and inches are rounded to the nearest inch. For your exact height, use the calculator above.

Worked example

Take an adult who is 170 cm tall and weighs 70 kg:

  1. Height in metres = 1.70, so height squared = 1.70 × 1.70 = 2.89.
  2. BMI = 70 ÷ 2.89 = 24.22, shown as 24.2.
  3. 24.2 is between 18.5 and 24.9, so it’s in the healthy weight range.
  4. At 170 cm, the healthy range runs from 53.5 kg (18.5 × 2.89) to about 72 kg (24.9 × 2.89).

In pounds and inches, take a woman who is 5 ft 4 in tall and weighs 140 lb:

  1. Height = 5 × 12 + 4 = 64 inches, and 64 × 64 = 4,096.
  2. BMI = 703 × 140 ÷ 4,096 = 24.03, shown as 24.0, which is a healthy weight.
  3. At 5 ft 4 in, the healthy range is about 108 to 145 lb.

BMI for women and men

Women and men use the same BMI formula and the same categories. Where they differ is body composition. At the same BMI, women usually have more body fat than men. A 2000 study of 1,626 adults found that body fat at a given BMI depends on sex, age and ethnic group.

For men, muscle is the more common source of error. A man who lifts weights can have a BMI over 25 with little body fat, because BMI counts muscle and fat alike.

For women and men alike, measuring your waist fills a gap BMI leaves. The NHS says measuring your waist can give a better idea of your overall health, because it shows whether you carry extra weight around your middle.

What BMI doesn’t tell you

BMI is a starting point. Keep these limits in mind when you read your result:

  • Muscle. BMI can’t tell muscle from fat. The NHS notes that people with a lot of muscle can be classed as overweight or obese despite having low body fat. This often applies to athletes and people who train hard.
  • Older adults. The categories stay the same at every age, but what they mean for health may change. A 2014 meta-analysis of 32 studies of people aged 65 and over found that being overweight wasn’t linked to a higher risk of death, while a BMI below 23 was.
  • Ethnicity. A World Health Organization expert consultation found that many Asian populations face a higher risk of type 2 diabetes and heart disease at BMIs below 25, and suggested 23 and 27.5 as additional cut-off points for public health action. The NHS gives similar advice for people from Asian, Black African, African-Caribbean and Middle Eastern backgrounds.
  • Where you carry weight. Two people with the same BMI can store fat in very different places, and BMI doesn’t show where. The World Health Organization notes that waist circumference can also be used to identify overweight and obesity.
  • Pregnancy. The NHS says its adult BMI calculator shouldn’t be used during pregnancy, and the same goes for this one.

BMI for children and teens

This calculator is for adults only. For children and teens, the CDC explains that BMI is interpreted using sex-specific BMI-for-age percentiles, because body fat changes as children grow. The adult categories above don’t apply to them.

To check a child’s BMI, use the CDC child and teen BMI calculator (ages 2 to 19) or ask your child’s doctor.

Find your daily calorie target

FitDiary works out how much to eat from your age, height, weight and activity. Type what you ate in one sentence and see what’s left for today.

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See how the FitDiary calorie counter works.

Frequently asked questions

How do I calculate my BMI by hand?

Divide your weight in kilograms by your height in metres, then divide by your height in metres again. For 70 kg and 1.70 m: 70 ÷ 1.70 ÷ 1.70 = 24.2. In pounds and inches, multiply your weight by 703, then divide by your height in inches twice.

Is BMI different for women and men?

No. The formula and the adult categories are the same for both. What differs is body composition: at the same BMI, women usually carry more body fat than men, and very muscular men can score as overweight without much fat.

Is a BMI of 23.4 healthy for a woman?

23.4 is inside the healthy adult range of 18.5 to 24.9, for women and for men. Some health services use 23 as a lower threshold for people from Asian backgrounds, who can face higher health risks at a lower BMI.

Is 140 pounds overweight for a 5 ft 4 in woman?

At 5 ft 4 in, 140 lb gives a BMI of 24.0, which is within the healthy range. The healthy range at that height runs from about 108 to 145 lb.

What is a healthy weight for 170 cm?

At 170 cm (about 5 ft 7 in), a BMI of 18.5 to 24.9 means a weight of roughly 53.5 to 72 kg (118 to 159 lb). The table above gives the range for other heights.

What is a normal BMI for older adults?

The official adult categories are the same at every age. A 2014 review of studies in people aged 65 and over found that being overweight wasn’t linked to a higher risk of death, while a BMI below 23 was. The review’s authors suggest keeping an eye on weight in this group.

Is BMI a good indicator of health?

It’s a useful first check, but it has limits. It can’t tell muscle from fat and it doesn’t show where you carry weight. A waist measurement, blood pressure and blood tests give your doctor a fuller picture.

What should I do if my BMI is too high?

It’s a reason to look more closely. A doctor can check your waist, blood pressure and blood tests. If you decide to lose weight, many people find a small, steady calorie deficit easier to keep up than a strict diet. The TDEE and calorie deficit calculators on this site can help you set a target.

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