BMI of a 5′ 8″, 121 Pound Person

What is the BMI of a man or woman who weighs 121 pounds and is 5 foot 8 inches tall?
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Weight
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For a 5′ 8″ tall person who weighs 121 lbs:
BMI = 18.40
Note: BMI is the same for men and women

Am I Overweight?

Here are the BMI standards as set by the World Heath Organization:

BMICategory
< 18.5Underweight
18.5 - 25Healthy Weight
25 - 30Overweight
> 30Obese

In the United States, the average BMI for adults is 28.8.

BMI Formula

Metric
BMI = kg / m2

Imperial
BMI = (lbs * 0.45359237) / (inches * 0.0254)2

Simplified
BMI = 703 * lbs / inches2

Is BMI Worth Using?

Body Mass Index is a very simplistic method of determining whether a person is overweight. It does not taken into account a person's frame, gender, or muscularity. Furthermore, at least one study has suggested that slightly overweight people may live longer than people in the "normal" range.

Nevertheless, BMI is highly correlated with body fat % and is a decent enough yardstick of a healthy weight.

Body fat estimates for a person with a BMI of 18.40
These are rough estimates based on a formula, and do not reflect differences in muscularity, body types, etc...
Age Male Female
18 10.0% 20.8%
19 10.3% 21.1%
20 10.5% 21.3%
21 10.7% 21.5%
22 10.9% 21.7%
23 11.2% 22.0%
24 11.4% 22.2%
25 11.6% 22.4%
26 11.9% 22.7%
27 12.1% 22.9%
28 12.3% 23.1%
29 12.6% 23.4%
30 12.8% 23.6%
Age Male Female
31 13.0% 23.8%
32 13.2% 24.0%
33 13.5% 24.3%
34 13.7% 24.5%
35 13.9% 24.7%
36 14.2% 25.0%
37 14.4% 25.2%
38 14.6% 25.4%
39 14.9% 25.7%
40 15.1% 25.9%
41 15.3% 26.1%
42 15.5% 26.3%
43 15.8% 26.6%
Age Male Female
44 16.0% 26.8%
45 16.2% 27.0%
46 16.5% 27.3%
47 16.7% 27.5%
48 16.9% 27.7%
49 17.2% 28.0%
50 17.4% 28.2%
51 17.6% 28.4%
52 17.8% 28.6%
53 18.1% 28.9%
54 18.3% 29.1%
55 18.5% 29.3%