Health & medical New Zealand
BMI Calculator New Zealand
Body mass index (BMI) compares your weight with your height and is one of the quickest screening measures used by health services. Enter your height in centimetres and weight in kilograms to see your BMI, the adult category it falls in and the weight range that would sit in the healthy band.
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Your BMI
βCategory
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Healthy weight range
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Difference to the top of the healthy range
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Height in feet and inches
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The working
A screening number, not a diagnosis. General information only, not medical advice. Everyone is different, so speak to a doctor, dietitian or other health professional before you change your diet or exercise.
How do I calculate my BMI?
Divide your weight in kilograms by your height in metres, squared. At 175 cm and 80 kg the answer is 26.1, which is in the overweight band (25.0 to 29.9). For that height, the healthy band of 18.5 to 24.9 covers roughly 57 to 76 kg.
What BMI can and cannot tell you
BMI is useful because it is quick and consistent: it lets a doctor or nurse spot when weight may be affecting health risk. It works best as a first look across a population, and less well for an individual.
People with high muscle mass, older adults who have lost muscle, and people of different body builds can sit outside the usual bands without a problem. If your result surprises you, look at other signs such as your waist, fitness, blood pressure and how you feel.
Using the healthy range
The healthy range shown is the set of weights for your height that fall between 18.5 and 24.9. It is a guide, not a target to hit. Changes in weight are best made gradually and with support, and a GP, practice nurse or dietitian can help set a goal that suits you.
For energy needs, see the BMR and TDEE calculator, which shows daily energy in kilojoules, the unit used on New Zealand food labels.
To convert food label energy, use the kJ to calories converter.
How this is calculated
The rule, step by step, so you can check any figure by hand.
BMI = weight in kg Γ· (height in metres)Β²under 18.5 is the underweight band18.5 to 24.9 is the healthy band25.0 to 29.9 is the overweight band30.0 and above is the obese bandhealthy weight range = 18.5 and 24.9 Γ (height in metres)Β²
BMI is a ratio, not a measurement of body fat. It cannot tell muscle from fat, where fat is carried, or how fit someone is, so a very muscular person can score as overweight while someone with little muscle and a lot of fat can score as healthy.
The bands above are the standard adult categories. They do not apply to children and teenagers, whose healthy range changes with age and sex and is read from growth charts by a health professional.
A worked example
An adult who is 175 cm tall and weighs 80 kg.
- Height in metres, squared3.0625
- BMI26.1
- CategoryOverweight
- Healthy weight range for this height56.7 to 76.3 kg
- Above the top of the range3.7 kg
A BMI of 26.1.
A waist measurement and a conversation with a doctor give a fuller picture than BMI alone.
Children and teenagers
The adult bands should not be used for anyone under 18. Growth charts compare a child's BMI with others of the same age and sex, and a health professional reads them. If you are worried about a child's weight, speak to a GP or Well Child provider.
Other measures
Waist circumference, blood pressure, blood sugar and cholesterol all add to the picture. A health check with your doctor looks at these together rather than relying on BMI alone.
What this calculator does not do
- Adults only
- Does not measure body fat
- A screening number, not a diagnosis
- Standard bands applied to everyone
Common questions
What is a healthy BMI?
For adults, 18.5 to 24.9 is the standard healthy band.
Is BMI accurate for athletes?
Not always. Muscle weighs more than fat, so muscular people can score high.
Can children use this calculator?
No. Children's results are read from growth charts by a health professional.
Does BMI measure body fat?
No. It is a ratio of weight to height.
What else should I look at?
Waist size, fitness, blood pressure and your doctor's advice.
Where these numbers come from
- Ministry of Health β ManatΕ« Hauora Government health information
Method last reviewed 2026-10-28 This calculator uses fixed rules rather than rates that change, and its method is re-checked against the sources above at least once a year. Out of date? Tell us and we will fix it.
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