BMI Calculator

What is BMI?

BMI stands for body mass index. It is a formula that’s used to calculate if you are in a healthy weight range for your height. Using a BMI calculator can show you whether you fall into an underweight, healthy, overweight, or obese weight range. It’s always good to know your BMI as it can help you stay in a healthy weight range.

While a BMI calculator is helpful for many reasons, the formula doesn’t take into account age, gender, body composition, or ethnicity. For this reason it’s a good idea to use the BMI calculator as well as taking your waist measurements. Finding your waist circumference can make you conscious of any potential risk factors by measuring how much fat is around your midline.

How a BMI calculator works

A BMI calculator uses a very simple formula to calculate whether you are in a healthy weight range for your height. All you need to find your BMI is your height and weight. The formula for a BMI calculator is BMI = kg/m2, where kg is your weight in kilograms and m2 is your height in metres, squared.

How do I use a BMI calculator?

Before you use a BMI calculator to lose weight, you have to first take some measurements.

1. Measure your weight for the BMI calculator

• When measuring your height for a BMI calculator, make sure you use scales that are on a hard and even surface.
• Use the same scales to measure your weight as some scales have different findings.
• Try to weigh yourself first thing in the morning if possible, and remove all shoes and heavy clothing.
• Stand in the middle of the scale and distribute your weight evenly between both feet.
• Record your weight for the BMI calculator in kg.

2. Measure your height for the BMI calculator

• First, find a partner to take your height for you as it’s too difficult to get a precise measurement on your own.
• Fix a tape measure to the bottom of a straight, rigid wall, making sure it is sitting at floor level.
• Again, remove any heavy clothing, shoes, and headgear.
• Stand with your feet together and your entire back to the wall so the whole back of your body is against the wall.
• Have your partner hold a ruler parallel to the top of your head and record your height for the BMI calculator in cm.

3. Use the BMI calculator online to find your BMI

Use our BMI calculator below to find out whether you are in a healthy weight range for your height.

Using a BMI calculator to lose weight

Can a BMI calculator help you to lose weight? Well, it depends on what you do with the information it gives you! BMI calculators can be valuable tools when trying to lose weight or if you’re on a diet. Firstly, a BMI calculator can show you whether you are in a healthy weight range or if you need to think about going on a diet. A BMI calculator can also help you distinguish whether you fall into an overweight or obese weight range, helping you better understand your diet and exercise needs for weight loss. Finally, some BMI calculators also give you suggested daily calorie allowances so you can better manage your diet and fitness goals.

What’s a healthy BMI for adults?

A healthy BMI for adults is between 18.5 and 24.9. Here’s how to use your BMI calculator findings:
Under 18.5 – Underweight. Falling in this range could be a sign that you aren’t eating enough or potentially suffering from malnourishment or illness.

• 18.5 – 24.9 – Great work! You’re within a healthy weight range for young to middle-aged adults.
• 25.0 – 29.9 – Overweight. It’s a good idea to think about losing weight through a combination of diet and exercise.
• 30 and over – Obese. The best way to lose weight is through diet, exercise, and in some cases, medicine. Visit your doctor if you need any help and advice to shred those kilos!

Who shouldn’t use a BMI calculator?

While the BMI formula is accurate for many people, there are some who shouldn’t rely on a BMI calculator. This includes muscle builders, long-distance athletes, people running on treadmills,  pregnant women, and the elderly. While you might find BMI calculators for kids and teens, it is unlikely to give an accurate measurement of a healthy weight range. This is because kids and teens have a lower muscle mass because they haven’t finished growing, which can conflict with a BMI calculator’s findings.

The elderly can also have less muscle mass, putting them in a lower BMI range even if they are healthy. Athletes, on the other hand, have a higher muscle mass and so their BMI can be extremely high even though they are healthy. Pregnant women undergo many changes in their body composition, and so a BMI calculator is not an accurate reflection of a healthy weight range for pregnant women.

BMI calculator for kids

You may recall us saying that most BMI calculators won’t give accurate results for kids and teens. We’d just like to mention that there are some BMI calculators for teens and kids out there which rely on national survey results to compare your findings with other children of their age range. Instead of using a point system like other BMI formulas, BMI calculators for children use centiles.

Here’s how a BMI calculator would find a healthy weight range for young kids:

• Underweight – 2nd centile & under.
• Healthy – Between 2-91st centiles.
• Overweight – Between 91-97th centiles.
• Very overweight – 98th centile & above.

BMI calculators & your waist measurements

Using a BMI calculator along with your waist measurements lets you know if you’re carrying excess fat around your stomach. This can be a risk factor in heart disease, stroke, and type 2 diabetes but wouldn’t show up in a typical BMI calculator test. This means you can have a healthy BMI but still be at risk of having these issues.

So take a measurement of your waist, between the bottom of your ribs and the top of your hips. Make sure to take your measurement at the bottom of an exhale. If your waist is more than 94cm for men or 80cm for women, then you should try to lose weight. If your waist is more than 102cm for men or 88cm for women, then you’re at high risk and should get in touch with your GP.