Healthy weight BMI calculator
Working out your body mass index (BMI) is one way to find out if you are a healthy weight. For your tamariki, it is a way to find out if they are a healthy weight for their height and age.
BMI is unable to measure how healthy you or your tamariki are.
About BMI in adults
Your BMI estimates how much body fat you have and indicates your risk of getting diseases. This includes:
- heart disease
- type 2 diabetes
- stroke
- some types of cancer.
These are more common in people with more body fat. The higher your BMI, the higher your risk.
Most people over the age of 18 can use the BMI, but it does have some limits. It may:
- overestimate body fat if you are tall, an athlete or very muscular
- underestimate body fat if you are short, 70 or older or have lost muscle
- not be accurate for certain ethnic groups. People of Asian descent can have more body fat on a smaller frame so for this group, a healthy BMI range would be lower. Māori or Pacific people often have a higher bone density and more muscle mass. For these people, a healthy BMI range would be higher.
BMI calculator for adults
Finding out my BMI
You can find out your BMI by using the BMI calculator on the Heart Foundation website. The calculator will tell you if you are underweight, a healthy weight, overweight (a slightly unhealthy weight) or obese (a very unhealthy weight).
You will need to know your height in centimetres and your weight in kilograms. The calculator will tell you if you are underweight, a healthy weight, a slightly unhealthy weight or a very unhealthy weight.
What is body mass index — Heart Foundation (external link)
Waist measurements
Measuring your waist is a good way to check that you do not have too much fat around your stomach. You can have a healthy BMI and still have too much tummy fat, which can also raise your risk of heart disease, type 2 diabetes and stroke.
What waist measurements mean for your heart — Heart Foundation (external link)
BMI results for adults
Your BMI result is best interpreted by your healthcare provider who has more information about you and your overall health.
Being underweight could be a sign that you are not eating enough, or you have an underlying health issue. Talk to your healthcare provider.
This is a healthy BMI range. Continue to maintain a healthy weight by being physically active and eating well.
Not everyone who has a BMI of 25 or more needs to lose weight For some people who are a very unhealthy weight (a BMI of 30 or over), losing 5 to 10 % of their weight (for example, losing 5 to 10 kg if you weight 100 kg) will make a big difference to their health and the way they feel. Talk to your healthcare provider.
If you need to lose weight
If you need to lose weight the best way to do this is by eating well, being more active, getting enough sleep and managing stress Talk to your healthcare provider for more information.
Eating well for good health (internal link)
BMI calculator for children
Finding out my child's BMI
If your tamaiti is at least 2 years old you can find out their BMI by using the BMI calculator on the Jack of All Organs website. You will need to use this calculator to measure your child's BMI because BMI is measured differently for adults. The calculator will tell you if your tamaiti is underweight, normal (a healthy weight), overweight (a slightly unhealthy weight) or obese (a very unhealthy weight) for their height and age.
BMI results for children
Results for tamariki will be given in percentiles. This will compare your tamaiti against other tamariki with the same sex and age. For example, a girl on the 80th percentile has a BMI score higher than 80 out of 100 other girls her age.
Regardless of the BMI result, if you have concerns about their eating, activity levels, sleep, screen time or overall wellbeing, talk to your healthcare provider. They will be able to check for any underlying health conditions. They may also be able to refer your whānau for healthy lifestyle support.
If your tamaiti is underweight, it might be because they have inherited this from you or their other parent. But it could mean they are not eating enough, or they have an underlying health issue. Make an appointment to see your healthcare provider.
Your tamaiti is likely to be a healthy weight for their height. Aim to instil healthy habits in your whānau so you and your tamariki can enjoy good health for life.
If your tamaiti is an unhealthy weight, they are more likely to develop health problems. This can include:
- high blood pressure
- type 2 diabetes
- breathing problems
- joint problems.
If they are an unhealthy weight and still growing, they do not need to lose weight. Staying the same weight while they grow taller will mean they will become a healthier weight for their height over time.
If you are concerned about their weight, talk to your healthcare provider.