No blood alcohol calculator is 100% accurate. There are many factors that effect the absorption and burn off rates of different people. These include metabolism rates, several health issues with the combination of medications that may be taken, drinking frequency, amount of food in the stomach and small intestine and when it was eaten, and more. This is only a rough estimation of the BAC level based on the above known inputs. This is not a guideline for how much you can drink and still bike safely or avoid being arrested!

The best policy is "Park it if you pour - don't drink and bike at all."

Alcohol Content Guide
Beer/Wine  5.0 to 13.0%
Sherry/Vermouth/Cizano  14 to 20%
Shot of Light Gin/Vodka/Rum  37.5%
Shot of Dark Whiskey/Brandy/Rum 40%

• 0.02% -0.03% BAC: No loss of coordination, slight euphoria and loss of shyness. Depressant effects are not apparent.
• 0.04% - 0.06% BAC: Feeling of well-being, relaxation, lower inhibitions, sensation of warmth. Euphoria. Some minor impairment of reasoning and memory, lowering of caution.
• 0.07% - 0.09% BAC: Slight impairment of balance, speech, vision, reaction time, and hearing. Euphoria. Judgment and self- control are reduced, and caution, reason and memory are impaired. .08 is considered legally drunk in most states.
• 0.10% - 0.125% BAC: Significant impairment of motor coordination and loss of good judgment. Speech may be slurred; balance, vision, reaction time and hearing will be impaired. Euphoria. It is illegal to operate a motor vehicle at this level of intoxication.
• 0.15% -0.15% BAC: Gross motor impairment and lack of physical control. Blurred vision and major loss of balance. Euphoria is reduced and dysphoria is beginning to appear.
• 0.16% -0.20% BAC: Dysphoria (anxiety, restlessness) predominates, nausea may appear. Appearance of a "sloppy drunk."
• 0.25% BAC: Needs assistance walking; total mental confusion. Dysphoria w/nausea and vomiting.
• 0.30% BAC: Loss of consciousness.
• 0.40% BAC and up: Onset of coma, possible death due to respiratory arrest.

Source http://www.indiana.edu/~adic/effects.html | More info from Wikipedia...