Body Mass Index (BMI)

BMI Calculator for Women: Sample Calculation

Body Mass Index ﹣ BMI Calculator - Women

Being overweight is bad for your health; losing weight is good for you. However, there is no such thing as an ideal weight for every woman. A pound figure alone does not take into account the age or the size of the female body. Therefore, the body mass index, or BMI, is the standard for assessing body mass.

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Age-dependent assessment of weight in women

Weight classification using BMI according to WHO is independent of age and gender for research purposes. However, to take into account the influence of these factors on weight, the calculator uses the more sophisticated classifications of the German Nutrition Society (gender-dependent) and the National Academies of Sciences, Engineering, and Medicine (age-dependent).

The calculation of the Body Mass Index for women

Mathematically, a woman needs two initial values for the calculation of the BMI:

  • Body height
  • Body weight

The BMI is calculated from the quotient between the body mass (the weight) and the body length squared. The formula is as follows:

BMI = body mass in kg / (height in metres)²

or translated to the Anglo-American units

BMI = 703 × body mass in lbs / (height in inches)²

An example:

A 30-year-old woman with a height of 5 feet and 7 inches (total 67 inches) weighs 155 pounds. We insert that into the formula. To make it easier, we first determine the square number of 67 - that is 4489 (67×67).

The BMI is then 703 × 155 / 4489 = 24.28.

Our calculator helps

For those who do not want to calculate alone, there are various BMI calculators available on the internet. The advantage of our BMI calculator is that it not only determines the "naked" truth as a number, but also evaluates the result immediately. It also takes into account the age of the user, because different ideal values apply to different age groups. And of course our calculator can also be used to determine the BMI for the male partner.

Normal or obese - only the assessment of the BMI for women brings certainty

The BMI of 24.28 alone says nothing about whether the woman is of normal weight or whether she is overweight. For the assessment of BMI, the German Nutrition Society (DGE) has developed a classification that takes gender into account. The American National Research Center goes in the other direction and bases its assessment of BMI on age. Our calculator combines both assessments - a graph tells you where you lie. The woman in our example has an "age-related normal weight".

The classification of BMI distinguishes between

  • Underweight
  • Normal weight
  • Overweight

In the last category, obesity, a further distinction is made depending on the weight class

  • Overweight
  • Very overweight
  • Obesity (Grade II)
  • Obesity (Grade III)

According to the German DGE, these values apply specifically to women:

Categoryfemale
Underweight< 19
Normal weight19–23.9
Overweight24–29,9
Severe overweight30–34.9
Grade II obesity35–39.9
Grade III obesity≥40

By the way, differences in assessment between men and women only exist for BMI values up to overweight - all threshold values in the higher categories are the same.

According to the National Academies of Sciences, Engineering, and Medicine the ideal BMI value for women is

  • 19–24 aged 19–24
  • 20–25 aged 25-34
  • 21–26 aged 35–44
  • 22–27 aged 45–54
  • 23–28 aged 55–65
  • 24–29 aged 65+

A distinction according to gender does not take place here.

What does a sample calculation look like?

A 44-year-old woman notes these data:

  • Body weight 200 lbs
  • Body length 5 feet and 7 inches (total 67 inches)

Using the above formula, it calculates:

  • BMI = 703 × body mass / height²
  • BMI = 703 × 200 lbs / (67 in)²
  • = 31.32 kg/m²

Our BMI calculator points out to the woman that she is severely overweight and strongly recommends weight reduction. The graphs show that a loss of just a few pounds could move her to the next more favourable class, in which case she would "only" be overweight. This increases her life expectancy; her health values improve and exercise becomes easier. Our BMI calculator motivates.

Can the BMI calculator be used for every woman?

Competitive athletes with a high muscle percentage, such as bodybuilders, will not be happy with the BMI formula. The starting value of the body mass, whether fat or muscle, is not taken into account. The BMI for strong female athletes will be significantly higher, and the classification will no longer fit. Their balanced diet and amount of exercise are likely to have a very positive effect their health.

The BMI also reaches its limits for pregnant women or young mothers who are breastfeeding. An assessment of weight during this time should be reserved for medically trained personnel. For female children and adolescents, there are special BMI calculators.

Source information

As source for the information in the 'Body Mass Index' category, we have used in particular:

Last update on November 29, 2022

The pages of the 'Body Mass Index' category were last editorially reviewed by Stefan Banse on November 29, 2022. They all correspond to the current status.

Previous changes on October 19, 2022

  • Editorial revision of all texts in this category