BMI calculator

BMI (body mass index) is your weight in kilograms divided by your height in metres squared. For adults, healthdirect lists a BMI under 18.5 as underweight, 18.5 to 24.9 as the healthy weight range, 25.0 to 29.9 as overweight and 30.0 or more as obese. At 175 cm and 80 kg, BMI is 26.1. It's a rough screening number, and it can't tell muscle from fat.

Height (cm)

Weight (kg)

Sex (for waist only)MaleFemale

Waist (cm, optional)

Adult BMI ranges

The calculator also shows the weight range that matches a BMI of 18.5 to 24.9 at your height. For 175 cm that's about 56.7 to 76.3 kg. Treat it as a wide band, not a goal weight.

Why lifters should take BMI with a grain of salt

BMI only knows your height and the number on the scale. Put on 5 kg of muscle and it reads the same as 5 kg of fat. healthdirect lists body builders and weightlifters among the people BMI is less accurate for, along with under-18s, pregnant women, people with a physical disability and several ethnic groups.

Waist measurement fills some of that gap because it tracks fat around the middle. healthdirect puts increased risk at 94 cm or more for men and 80 cm or more for women, and greatly increased risk at 102 cm and 88 cm. Measure on bare skin, halfway between your lowest rib and the top of your hip bone, after a normal breath out. Enter it above and the calculator tells you which side of those lines you're on.

If you train, your lifts, your waist and how your clothes fit say more about progress week to week than BMI does. KiloMate's weekly body check-in logs weight, waist and progress photos so you can see the trend.

Related tools

BMI says nothing about how much to eat. For that, start with the TDEE calculator or the calorie calculator, and set a protein target with the protein calculator.

Questions

How do I calculate my BMI?

Divide your weight in kilograms by your height in metres squared. At 80 kg and 175 cm that's 80 ÷ (1.75 × 1.75) = 26.1.

What is a healthy BMI in Australia?

healthdirect lists 18.5 to 24.9 as the healthy weight range for adults. Under 18.5 is underweight, 25.0 to 29.9 is overweight and 30.0 or more is obese. These are the same cut-offs the World Health Organization uses for overweight (25 or more) and obesity (30 or more).

Is BMI accurate if I lift weights?

Often not. BMI can't tell muscle from fat, and healthdirect names body builders, weightlifters and some high-performance athletes among the groups it is less accurate for. A muscular lifter can land in the overweight band with little body fat. Waist measurement is a useful second check.

What waist measurement increases health risk?

healthdirect says risk is increased at 94 cm or more for men and 80 cm or more for women, and greatly increased at 102 cm or more for men and 88 cm or more for women. Measure on bare skin, halfway between your lowest rib and the top of your hip bone, after breathing out normally.

Who shouldn't use a BMI calculator?

healthdirect says BMI is less accurate for people under 18, pregnant women, people with a physical disability, and people from some ethnic groups, including Aboriginal and Torres Strait Islander peoples, Pacific Islander, Maori, South Asian, Chinese and Japanese people. Children's BMI is read against age and sex charts, which this calculator doesn't do.

Sources

1. healthdirect Australia. Body mass index (BMI) and waist circumference. Last reviewed December 2024, read 30 October 2026. healthdirect
2. World Health Organization. Obesity and overweight fact sheet, 7 October 2026: overweight is a BMI of 25 or more, obesity 30 or more. WHO

General information only, not medical advice. BMI is a screening measure, not a diagnosis. If you're worried about your weight, or about how you feel about food or your body, talk to a GP. The Butterfly National Helpline is 1800 33 4673.