High body fat can increase the risk of conditions, such as diabetes and cardiovascular disease. Too little body fat can also potentially harm a person’s fertility, immunity, and heart health.

Body mass index (BMI) is a rough estimate of body fat percentage. It is useful as a rough guide. However, it has limitations. For example, people with high muscle mass may have a high BMI without high body fat.

Accurately measuring body fat is essential for assessing health risks.

In this article, learn about ideal body fat percentages for men and women by age, as well as how to calculate BMI.

Physiologically, women need more essential body fat than men. As such, women require slightly more body fat for good health.

Essential body fat is necessary for insulation, the protection of internal organs, vitamin storage, and hormone regulation to promote a healthy pregnancy.

Body fat also changes with age.

Ideal body fat percentages by age group are as follows:

Age 20–29

CategoryPercentage
dangerously lowunder 14%
excellent14–16.5%
good16.6–19.4%
fair19.5–22.7%
poor22.8–27.1%
dangerously highover 27.2%

Age 30–39

CategoryPercentage
dangerously lowunder 14%
excellent14–17.4%
good17.5–20.8%
fair20.9–24.6%
poor24.7-29.1%
dangerously highover 29.2%

Age 40–49

CategoryPercentage
dangerously lowunder 14%
excellent14–19.8%
good19.9–23.8%
fair23.9–27.6%
poor27.7–31.9%
dangerously highover 31.3%

Age 50–59

CategoryPercentage
dangerously lowunder 14%
excellent14–22.5%
good22.6–27%
fair27.1–30.4%
poor30.5–34.5%
dangerously highover 34.6%

60-69

CategoryPercentage
dangerously lowunder 14%
excellent14–23.2%
good23.3–27.9%
fair28–31.3%
poor31.4–35.4%
dangerously highover 35.5%

Men also need to keep their body fat percentage in a healthy range. However, the ideal fat percentages are slightly lower in men than in women.

Ideal body fat percentages by age group are as follows:

Age 20–29

CategoryPercentage
dangerously lowunder 8%
excellent8–10.5%
good10.6–14.8%
fair14.9–18.6%
poor18.7–23.1%
dangerously highover 23.2%

Age 30–39

CategoryPercentage
dangerously lowunder 8%
excellent8–14.5%
good14.6–18.2%
fair18.3–21.3%
poor21.4–24.9%
dangerously highover 25%

Age 40–49

CategoryPercentage
dangerously lowunder 8%
excellent8–17.4%
good17.5–20.6%
fair20.7–23.4%
poor23.5–26.6%
dangerously highover 26.7%

Age 50–59

CategoryPercentage
dangerously lowunder 8%
excellent8–19.1%
good19.2–22.1%
fair22.2–24.6%
poor24.7–27.8%
dangerously highover 27.9%

60-69

CategoryPercentage
dangerously lowunder 8%
excellent8–19.7%
good19.8–22.6%
fair22.7–25.2%
poor25.3–28.4%
dangerously highover 28.5%

There is no single formula to accurately calculate a person’s body fat percentage.

The best way to measure body fat involves using specialized equipment, usually in a doctor’s office. A doctor can use fat calipers to calculate fat percentages in specific areas of the body.

There are several other accurate ways to assess body fat. These include underwater weighing, X-rays, and air displacement plethysmography.

Measuring BMI is another way to estimate body fat. Although this method has limitations, BMI does correlate well with body fat in most people. It is also quicker and easier than other methods of measuring body fat.

The National Institutes of Health (NIH) offers a free BMI calculator and height- and weight-based BMI chart.

The formula for calculating BMI is (weight in pounds x 703) / (height in inches)2.

To calculate BMI, a person should:

  1. multiply their weight in pounds by 703
  2. multiply their height in inches by itself
  3. divide the answer from Step 1 by the answer from Step 2 to calculate their BMI

To interpret the final number, a BMI:

  • below 18.5 means a person is underweight
  • between 18.5 and 24.9 means a person is of a “normal,” or healthy, weight
  • between 25 and 29.9 indicates a person is overweight
  • above 30 indicates a person has obesity

Assessments of body fat consistently show that people have higher body fat percentages than official guidelines recommend. Even healthy people can have unusually high body fat.

These differences raise concerns about whether or not ideal body fat percentages are realistic.

Average body fat percentages also vary across race and ethnicity. This suggests there may be cultural or racial bias with body fat percentage ideals.

Using BMI to assess body fat or overall health is another issue. BMI only accounts for weight. It makes no distinction between lean muscle, body fat percentage, and bone mass.

These factors are relevant to overall health and assessing body fat. For example, the BMI of a person with high bone density and muscle mass may indicate they have high body fat.

Also, BMI cannot assess where fat is in the body. The location of body fat is also relevant to overall health. For example, fat around the abdomen has higher health risks than fat in other areas.

There are many limitations to BMI and measuring body fat. Having a high body fat percentage or BMI does not always lead to health problems. However, this method does still provide a quick and useful clinical tool to assess health risks.

It might be helpful to ask a doctor the following questions:

  • What is the ideal body fat percentage for people of my age, activity level, and sex?
  • What is the most accurate way to calculate body fat percentage?
  • Does my health status suggest that a body fat percentage test might be helpful?
  • What can I do to be healthier?
  • Am I at a moderate weight?

Accurately calculating body fat percentages at home is challenging. However, using BMI calculations or fat calipers can give a rough estimate of body fat.

Body fat is a useful indicator of overall health. However, there are limitations to its use.

Rather than focusing on body fat alone, consider prioritizing an overall healthy lifestyle. Exercising more, doing regular strength training, and eating a balanced diet are good ways to maintain good health.