A BMI Calculator for Kids With Chart

A BMI Calculator for Kids With Chart

Calculating BMI, or body mass index, is a reliable way to determine whether your weight is within a healthy range. A body mass index that’s high can indicate the potential for health risks, while a BMI that’s in a healthy range means you’re less likely to suffer those risks.

But what about kids? Does BMI work for kids, too? There are a few things you need to know about how body mass index works when you’re dealing with children. For example, do you know:

  • How to calculate your child’s BMI?
  • If BMI is the same for kids as it is for adults?
  • If a high BMI in a child means the same thing as a high BMI for an adult?

Here’s everything you need to know about calculating a child’s BMI, and what information you can derive from the results.

How to Find Your Child’s BMI

Determining your child’s BMI is very simple – all you’ll need is a calculator and a ruler. First, make sure your child isn’t wearing shoes, and that her hair isn’t up on top of her head. No hats, no bows – you get the idea. You want an exact measurement of your child’s height.

First, ask your kid to stand against a wall. The back of her head should be touching the wall, as should her shoulders, her heels and her bottom. In other words, make sure she’s standing up as straight as possible. The height of your child is measured at the height of the crown of her head. Take the measurement in meters.

Next, you’ll need your child’s weight. Because you took her measurement in meters, you’ll want to get her weight in kilograms. If you don’t have a way to do this, you can use an online calculator to convert pounds to kilograms easily.

Finally, to calculate your child’s BMI, you’ll use the formula Weight / (Height x Height). In other words, divide the child’s weight by her height, then divide it by the height again.

The number you get is your child’s BMI.

Do Kids Have a Different BMI Calculator than Adults?

Kids’ BMI and adults’ BMI is calculated in exactly the same way. An adult’s BMI is calculated by taking weight in kilograms and dividing that number by the height, then dividing by height again. There aren’t two seperate calculators – one for kids and one for adults.

But the way that information is used is quite differently. See, in adults, BMI is put on a linear scale. A BMI between 18.5 and 24.9 is considered healthy. Anything over that is considered overweight.

The body mass index of a child is measured in comparison to his peers. The reason for this is because kids grow at different rates and speeds. Some shoot up like weeds while others gain weight first.

There’s no one “right” way for a child to grow, or to gain weight based solely on age or other factors. That’s why, instead of a linear BMI chart, doctors use a BMI graph to determine the healthy ranges of BMI for kids.


So the BMI is Calculated, What About the Chart?

So, you’ve calculated your child’s BMI. What’s next? Unfortunately, without access to the chart, your kid’s BMI means very little. Again, kids grow at astoundingly different rates, and so it’s important to see where your kids growth lies in relation to other kids.

You’ve probably seen the kids’ BMI chart at the doctor’s office. It’s a grid, with a few wavy lines. Somewhere in the midst of those lines is your child’s BMI, and it’s expressed in terms of percentile.

The place on the chart where your child’s BMI falls will give you a very good indication if she is a healthy height and weight for her age. Here’s how the chart works:

  • If your child’s BMI is below the 5th percentile, she is considered underweight.
  • If your child’s BMI is between the 5th to the 85th percentile, that’s considered a healthy range for body mass index.
  • If your child’s BMI is over the 85th percentile, she is considered to be overweight.

As you can see, there is a huge range of percentiles where your child is considered healthy. As mentioned, kids are unique little people. Some grow tall while others gain weight. So while BMI in a child is important, it’s critical that you don’t interpret your child’s BMI data the same way you do your own.


Can My Child’s BMI Value Be Bad News on the Chart?

Yes! Absolutely! You probably already know that an adult with a high BMI is more likely to suffer heart disease, diabetes, joint pain and other illnesses. Well, children aren’t exempt!

If your child’s BMI is above the 85th percentile, you’ll want to talk to a doctor right away. Your child is likely to suffer serious side effects from being overweight or obese, and these side effects can be very harmful – even fatal!

Diseases in children that are caused by a high BMI include:

  • Heart disease
  • Heart attack
  • Type 2 diabetes
  • High cholesterol
  • High blood pressure
  • Low self esteem
  • Depression and suicidal thoughts

Of course, children who are overweight are also more likely to be picked on in school, singled out by peers for their weight. This can cause further psychological damage, which may perpetuate the weight gain.

If your child is overweight or has a high BMI, please talk to your doctor sooner than later. It may mean the difference between good health and poor health for your child – for the rest of his life.

How Can I Help Control My Child’s BMI?

Weight gain and a high BMI in children can be caused by a number of factors. While some factors are physiologically based, there are a number of other reasons for weight gain in your child that you have complete control over.


The first of these, of course, is food. To put it simply, children eat the food they’re given. This is particularly true for the younger ones who don’t have access to money for the store or vending machines at school.

Put another way, if there are cookies in the pantry, it’s because someone put them there. And there’s a good chance it wasn’t your child who did so. If you’re concerned about your child’s BMI, lead by example. Remove the fatty, sugary foods from your home. Serve healthful, nutrient-rich meals. And choose to eat better, yourself.


An Inactive Lifestyle

More and more, kids are getting less physical activity. In many countries, an emphasis is placed so heavily on academics like literacy and maths that there’s little time for children to just go kick around a ball, or run around in the schoolyard.

When he’s home, encourage your child to move around. You can do this however you like. Take a walk together, as a family. Pay him to rake leaves. Or simply remove the video game controller from his hand.

An inactive lifestyle is a huge contributor to weight gain and high BMI. Encourage your kid to, well, be a kid. Playing outside is what kids do best.



If you’ve noticed a sudden weight gain in your child, it could be due to external stressors. The best way to narrow down the source of this stress is, simply, to ask your child. The trouble could be family related or related to his friends at school. Or it could be something as simple as hormones and puberty.

Talk to your child to get a feel for whether something is bothering him. If he doesn’t feel comfortable opening up to you, invite the school guidance counselor to speak with your child.

Is Your Child’s BMI Healthy?

Now you know how to calculate your child’s BMI, and how to interpret that information. Just as adults can suffer health problems due to obesity, overweight children are more likely to suffer heart conditions, high blood pressure and more.

Take control of your child’s BMI today – it could mean a healthier child tomorrow.


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