How Much Should I Weigh For My Age & Height?

Original article date: 23 May 2010, Article updated: 4 March 2014

One of the most common questions received in our feedback emails is "how much should I weigh for my age and height?" In this article, we will explain the most common ways in which this can be calculated. 

 

To determine how much you should weigh (your ideal body weight) several factors should be considered, including age, muscle-fat ratio, height, sex, and bone density. 

Some people suggest that calculating your Body Mass Index (BMI) is the best way to decide whether your body weight is ideal. Others say that BMI is faulty as it does not account for muscle mass and that waist-hip ratio is better. 

One person's ideal body weight may be completely different from another's. If you compare yourself to family and friends you risk either aiming too high if you are surrounded by obese or overweight people, or too low if everyone around you works as fashion models. 

Even comparing yourself with people outside your immediate surroundings may not work.

The levels of overweight and obesity in one country, such as the USA or UK, are much higher than in The Netherlands. So a Dutch person may aim for a lower ideal weight than an American if all he did was to compare himself to other people. 

A recent study may have turned national guidelines on people’s ideal weight on its head. Researchers found that overweight people have a lower all-cause mortality risk compared to those of normal weight.

Is Body Mass Index (BMI) a good measure?

Your BMI is your weight in relation to your height.

• BMI metric units: Your weight (kilograms) divided by the square of your height (meters)
  e.g. Weight 80 kilograms. Height 1.8 meters.
  1.8² meters = 3.24
  80 divided by 3.24 = BMI 24.69.
• Imperial units: Your weight (pounds) times 703, divided by the square of your height in inches.
  e.g. Weight 190 pounds. Height 6 ft (72 inches)
  72² = 5184
  190 x 703 divided by 5184 = BMI 25.76

Health authorities worldwide mostly agree that:

• People with a BMI of less than 18.5 are underweight.
• A BMI of between 18.5 and 25 is ideal.
• Somebody with a BMI between 25 and 30 is classed as overweight.
• A person with a BMI over 30 is obese.

In some countries health authorities say the lower limit for BMI is 20, anything below it is underweight.

Calculate Your BMI

To calculate your BMI you can use our metric BMI calculator below (requires Flash) or, alternatively, use our more comprehensive BMI Calculator.

What is the problem with BMI?

BMI is a very simple measurement which does not take into account the person's waist, chest or hip measurements. An Olympic 100 meters sprint champion may have a BMI higher than a couch potato of the same height. The couch potato may have a big belly, not much muscle and a lot of body fat on his hips, upper thighs, in his blood and other parts of his body. While the athlete will have a smaller waist, much less body fat, and most likely enjoy better health. According to a purely BMI criteria, the couch potato is healthier. 

BMI does not take into account bone density (bone mass). A person with severe osteoporosis (very low bone density) may have a lower BMI than somebody else of the same height who is healthy, but the person with osteoporosis will have a larger waist, more body fat and weak bones. 

Many experts criticize BMI as not generally useful in evaluation of health. It is at best a rough ballpark basic standard that may indicate population variations, but should not be used for individuals in health care. 

Put simply: experts say that BMI underestimates the amount of body fat in overweight/obese people and overestimates it in lean or muscular people. 

More information on BMI, together with imperial and metric BMI calculators, is available here.

Nick Trefethen, a Professor of Numerical Analysis at Oxford University's Mathematical Institute, has created what he believes to be a better, more accurate and relevant formula than the BMI one for deciding whether people are carrying too much fat. Humans do not grow equally in all three dimensions, he explains - the existing BMI formula presumes we do.