Is a BMI of 18 underweight?
A BMI of 18 is higher than 12% of men worldwide and 4% of American men. For women it is the 14th percentile worldwide, and the WHO files it under "underweight".
UnderweightWHO category. BMI is a comparison with a population, not a diagnosis: it does not know muscle from fat, or where the weight sits.
BMI 18 by group
Men
Women
Percentile is the share of the group with a BMI below this one. “1 in X” counts the rarer side: people at or beyond this value above the median, at or under it below. Percentiles are estimated from a normal distribution with each group's mean and standard deviation.
What this means
- For a man of 180 cm (5 ft 11 in), a BMI of 18 is 58 kg (129 lb). For a woman of 165 cm (5 ft 5 in) it is 49 kg (108 lb).
- Across the 186 countries in our data, a BMI of 18 is most ordinary for men in Ethiopia, where it is higher than 35% of men, and stands out most in Tonga, where it is higher than 1%.
- BMI is weight divided by height squared. A rugby forward and a desk worker can share a number and little else, which is why doctors measure waists too.
Questions
- Is a BMI of 18 underweight?
- Yes by the WHO cut-offs: under 18.5 is underweight. A BMI of 18 is higher than 12% of men and 14% of women worldwide, and 4% of men and 6% of women in the United States.
- How common is a BMI of 18?
- Worldwide, about 1 in 8 men and 1 in 7 women have a BMI of 18 or less. The global mean is 24.5 for men and 24.8 for women.
- What weight is a BMI of 18?
- It depends on height. At 160 cm a BMI of 18 is 46 kg (102 lb); at 170 cm, 52 kg (115 lb); at 180 cm, 58 kg (129 lb); at 190 cm, 65 kg (143 lb).
Source: NCD Risk Factor Collaboration, Lancet 2017, age-standardised mean BMI for 2016. Country SDs where published, otherwise the global SD. Percentiles on this page are our estimate from a normal distribution with the stated mean and SD.
Height and weight in, your BMI and country percentile out.
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