What does your BMI mean?
Body mass index is a simple screening measure of whether your weight is in proportion to your height. The World Health Organization uses these adult categories:
Below 18.5: underweight 18.5-24.9: healthy weight 25-29.9: overweight 30-34.9: obesity class 1 35-39.9: obesity class 2 40 and above: obesity class 3
The healthy weight range shown under your result is the set of weights that keep BMI between 18.5 and 24.9 at your height. It is a broad band where health risk is lowest, not a single perfect number.
How is BMI calculated?
Metric: BMI = weight (kg) / (height (m) x height (m)). For example, someone who weighs 70 kg and is 1.75 m tall has a BMI of 70 / (1.75 x 1.75) = 22.9, which is in the healthy range.
US units: BMI = 703 x weight (lb) / (height (in) x height (in)). A person who is 5 ft 9 in (69 in) and 160 lb has a BMI of 703 x 160 / 4,761 = 23.6. The body analysis in the Kilotaki app uses the same formula and the same cut-offs.
How to interpret your result
As BMI rises, the statistical risk of type 2 diabetes, high blood pressure, heart disease and sleep apnea goes up. Values in the underweight range are linked to undernutrition, osteoporosis and weakened immunity.
If you are in the overweight range, losing just 5-10% of your body weight produces measurable improvements in blood pressure, blood sugar and cholesterol. Small, sustainable steps are more realistic than trying to reach the healthy range all at once. Tracking your weight regularly lets you read the trend instead of a single weigh-in.
Limitations of BMI
BMI does not tell muscle from fat. Muscular athletes can show up as overweight, while older adults who have lost muscle can have a high body fat percentage despite a normal BMI. It also ignores where fat is stored: fat around the abdomen is riskier than fat on the hips and thighs.
That is why BMI is more useful alongside waist circumference, waist-to-hip ratio or body fat percentage. In people of Asian descent, health risk can start at lower BMI values. This calculator is for adults over 18; children and teens are assessed with age- and sex-specific percentile charts. BMI is not interpreted this way during pregnancy.
When to see a doctor
Talk to a doctor if your BMI is 30 or above, below 18.5, or if you have lost more than 5% of your body weight without trying in the past six months. Weight-related symptoms such as high blood pressure, diabetes, joint pain or snoring are also worth checking. Your doctor can interpret BMI together with blood tests and other measurements to set a target that suits you.