Examining ones BMI is like reading ones horoscope on a Chinese restaurant placemat. It's so vague and fails to take into many additional considerations. Though you can probably tell by looking in the mirror, find out if you're overweight by calculating your BMI here. Above is a chart of American BMIs compared to those of our global neighbors. You can see a larger version of the chart here. Keep in mind that anything under 18.5 is considered underweight, so what the heck is going on in Japan?