Blood-Alcohol Levels
The two offenses an individual is most likely going to be charged with both deal largely with the chemical test results (blood, breath, or urine tests). The results of the chemical test will determine the charges and possible sentences the individual will receive. The “DUI” offense (or driving under the influence) is, in part, decided by the chemical test results with a refutable assumption that the individual was intoxicated if these results .08% or greater. The so-called “per se” offense is determined entirely upon the chemical test results, as a “per se” offence is defined by driving with a blood alcohol level at or above .08%.
It must be noted that all DUI laws are based on the blood-alcohol level of the suspect WHILE DRIVING, not when the chemical test is administered. The disparity of the test results could be great if a significant amount of time has passed between the initial interrogations and the chemical test. It should also be noted that there are some inconsistencies with the instruments used for the tests. A properly trained attorney will have the ability to challenge the validity of the results, the calibrations of the machines, and the training of the arresting officer.
About.com
Simple alcohol level calculator using weight of person drinking, hours spent drinking, amount consumed and percentage of alcohol.
Wikipedia
Extensive coverage of scientific and legal aspects of blood alcohol levels.
Calculate Your Blood Alcohol Online
An online calculator provided by the University of Oklahoma Police Department.