That's because the charts are simplified/condensed, some more than others. A lot have 5lb increments while this one has 10lb. I attached the one I like to use where you plug in your actual numbers and it calculates it with decimal points.

http://www.nhlbi.nih.gov/health/educational/lose_wt/BMI/bmicalc.htm

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Actually it's worse than you think. Many people who calculate their BMI to be within a "healthy" range still are carrying too much body fat and are still at risk of health conditions.

Many people like to site those few false positives identified as overweight because of their tremendous amount of muscle (just 1% of females and 5% of males fall into this trap), but the real failing is how many more people it says they're at a healthy weight when really, they're not. Some studies suggest it's as high as 50% particularly in females who are identified by BMI as in a 'healthy' weight range but still carry too much body fat.

BMI was never intended to be a diagnostic tool on the individual - it was intended to be used on groups of people or at worst - a basic screening tool that's simple to use to identify those at highest risk of carrying too much body fat.

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I use the one that auto pops up when you google BMI calculators but I didn't notice it doesn't take sex into account... Is it supposed to? ... I think so! Men and women have different bodies, men usually weigh more without being overweight and have a higher muscle to body fat ratio than girls, ... More on reddit.com

The answer is quite often but not most of the time. And the fact is that it's not only saying muscular men are OBESE (EDIT: while the article uses the term "obese" it is using the BMI cut-off for "overweight" and not "obese" so the inaccuracies aren't of the same magnitude that the articles wording suggest) , its also telling women with obesity(EDIT: Read "overweight") levels of body fat they they have a healthy BMI. BMI is still accurate over 80% of the time and unless you are a ripped guy your BMI either reflects your fat levels accurately or in the case of many women actually underestimates the levels of fat. For the majority of people it's a decent indicator of their body fat. More on reddit.com