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Calculate BMI

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To calculate your BMI, enter your height and weight in the form below,
either metric or imperial.

HeightWeight BMICalculate BMI

BMI table

BMI values according to WHO.

BMI rangeWeight category
Underweight
-15.99Severe thinness
16.00-16.99Moderate thinness
17.00-18.49Mild thinness
18.50-24.99Normal weight
25.00-29.99Overweight
30.00-34.99Obese - class I
35.00-39.99Obese - class II
40-Obese - class III

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What is BMI?

BMI means Body Mass Index. The BMI shows the relation between a person's height and weight, and can be used to indicate whether the person has a normal weight or if he/she is underweight or overweight. BMI can also be called the Quetelet index, after its inventor, the Belgian scientist Adolphe Quetelet (1796-1874).

It is important to note that BMI is not actually a measurement for the percentage of body fat, and is not applicable to everybody (e.g. persons with a large muscle mass or bodybuilders).

For children and teenagers BMI is calculated the same way, but the thresholds for overweight, normal weight and underweight depends on the age and gender of the child. The BMI table that is being used for adults is not applicable to children and teenagers.

How to calculate Body Mass Index

Mathematically, BMI is kg/m2 (kilograms per square meter).

BMI formula

BMI =
(bodyweight in kg)
(bodyheight in meters)2
=
(weight in kg)
(height in meters) * (height in meters)

BMI calculation example

Example: A person is 175 cm tall and has a weight of 70 kg.

BMI =
70
1.752
=
70
1.75 * 1.75
=
70
3.0625
= 22.86 (normal weight)

How to calculate BMI with imperial units: feet

To use pounds (lb) and feet (ft) instead of kilograms (kg) and meters (m), use the same fomula, but multiply the weight by 4.88.

BMI formula for pounds and feet

BMI =
(bodyweight in pounds) * 4.88
(bodyheight in feet)2
=
(weight in pounds) * 4.88
(height in feet) * (height in feet)

BMI calculation example (feet)

Example: A person is 5'6" tall and has a weight of 160 lb.

5'6" = 5 + (6/12) = 5.5'

BMI =
160 * 4.88
5.52
=
780.8
5.5 * 5.5
=
780.8
30.25
= 25.81 (overweight)

Why the factor 4.88?

1 lb = 0.45359237 kg

1 ft = 0.3048 m

w * 0.45359237 kg
(h * 0.3048)2 m2
=
w * 0.45359237 kg
h2 * 0.09290304 m2
=
w * 4.8824276... kg
h2 m2

Where w is the weight in pounds, and h is the height in feet.

How to calculate BMI with imperial units: inches

To use pounds (lb) and inches (in) instead of kilograms (kg) and meters (m), multiply the weight by 703.

BMI formula for pounds and inches

BMI =
(bodyweight in pounds) * 703
(bodyheight in inches)2
=
(weight in pounds) * 703
(height in inches) * (height in inches)

BMI calculation example (inches)

Example: A person is 5'6" tall and has a weight of 100 lb.

5'6" = (5*12) + 6 = 60 + 6 = 66"

BMI =
100 * 703
662
=
70300
66 * 66
=
70300
4356
= 16.14 (underweight: moderate thinness)

Why the factor 703?

1 lb = 0.45359237 kg

1 in = 0.0254 m

w * 0.45359237 kg
(h * 0.0254)2 m2
=
w * 0.45359237 kg
h2 * 0.00064516 m2
=
w * 703.0695796... kg
h2 m2

Where w is the weight in pounds, and h is the height in inches.

BMI Prime

BMI Prime is the BMI relative to the upper limit for normal weight. I.e. when the BMI is at the upper limit for normal weight, BMI Prime is 1.00. A BMI Prime value larger than 1.00 indicates overweight. For normal weight (BMI 18.5 - 25) the value of BMI Prime is between 0.74 and 1.00.

For Asian body types, BMI Prime should be between 0.80 and 1.00 (BMI 18.5 - 23 for normal weight). Please note that there may be differences in which BMI is considered to be the upper limit for normal weight.

BMI Prime formula


The formula to calculate BMI Prime is very simple:

BMI Prime =
BMI
25

BMI Prime formula for Asian body types

Since the upper limit for normal weight is often lower for Asian body types, the formula for BMI Prime looks like this:

BMI Prime =
BMI
23

Please note that there may be differences in which BMI is considered to be the upper limit for normal weight.

How to lose weight?

In theory it is simple to lose weight. Use more energy than you take in (eat).

However, in practice it is not so simple as it may sound, since it requires a lot of self control and hard work. But do not give up! If you really put your mind to it, you can do it. A good start could be to have a nice walk for at least 30-60 minutes every day. If you think it is boring, you could listen to music or audio books while walking, or walk with a friend.

If you start working out more than you are used to, you should consult your doctor first.

Learn more about BMI and weight loss

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