Are online BAC charts accurate?

It may seem that consulting an online blood alcohol content (BAC) chart would be a good way to help you drink responsibly, but these charts aren't always accurate. Online BAC charts are intended to estimate your level of impairment. They are not an indicator that you are always safe to drive. Some factors that can influence the accuracy of these charts include:

• Rate of alcohol consumption. Sipping a drink minimizes the effects of alcohol, while rapidly gulping down drinks increases intoxication because the liver can't keep up. BAC charts are calculated based on a standard rate of one drink per hour.
• Serving size. BAC charts assume that one beer is 12 oz. with 4.5% alcohol content, one glass of wine is 4 oz. with 15% alcohol content, and one shot of hard liquor is 1.5 oz. with 40% alcohol content. If you're not paying close attention to these serving sizes, you can seriously underestimate your level of impairment.
• Past drinking habits. Someone who regularly drinks alcohol will likely have a higher tolerance than someone who seldom or never drinks.
• Genetics. Some people have a low genetic tolerance to alcohol due to a lack of enzymes necessary to break down a drink. Having a condition that gives you a higher or lower than average metabolism can also affect the accuracy of an online BAC chart.
• Time of last meal. If you haven't eaten in quite some time, you'll be impaired much more quickly than someone who recently had a big meal.

While online BAC charts are not 100% accurate, it's also worth pointing out that the sobriety tests a law enforcement officer uses during a DUI stop are not infallible either. Having low blood sugar, taking certain prescription medications, or recently suffering from an inner ear infection are just a few examples of special circumstances that can lead to inaccurate test results.