(Newser) – It's that magical line that we try to avoid crossing while out on the town: a blood-alcohol concentration of .08%. And as the Wall Street Journal reports, most of us figure a few glasses of wine over dinner won't put us over the legal limit. The paper set out to test our assumptions: It threw a "BAC party," in which guests enjoyed alcohol, then blew into three different models of breathalyzers throughout the evening. So what's the magic number of "safe" drinks? The Journal discovers, frustratingly, it's a question with no consistent answer. Because one's BAC is not just individual, it's dependent on changing factors.

Among the things that affect your BAC:

Food: Eating while drinking slows down how fast booze gets absorbed into the bloodstream—it stays in the stomach longer as part of the digestion process before heading to the small intestine and liver. What you eat barely matters, however.

Eating while drinking slows down how fast booze gets absorbed into the bloodstream—it stays in the stomach longer as part of the digestion process before heading to the small intestine and liver. What you eat barely matters, however. Weight trumps height: A woman who is 5-foot-5 and 140 pounds and a woman who is 5-foot-9 and 140 pounds will have similar BACs after drinking the same amount. But that first woman's BAC will be lower than that of a woman who is 5-foot-5 and 120 pounds.

A woman who is 5-foot-5 and 140 pounds and a woman who is 5-foot-9 and 140 pounds will have similar BACs after drinking the same amount. But that first woman's BAC will be lower than that of a woman who is 5-foot-5 and 120 pounds. Age: The bodies of younger drinkers metabolize alcohol quicker than those of older drinkers.

The bodies of younger drinkers metabolize alcohol quicker than those of older drinkers. Menstrual cycles: Women are able to metabolize alcohol 10% faster right after ovulation.

Women are able to metabolize alcohol 10% faster right after ovulation. Random stuff: ...like how tired, stressed, or depressed you are, as well as whether you're sick, affects things.

...like how tired, stressed, or depressed you are, as well as whether you're sick, affects things. What you're drinking: Shots and carbonated drinks raise your BAC faster.

Click through for more things that can affect your BAC . (Read more blood alcohol level stories.)