Alcohol content in blood is measured either as a percentage by mass or by mass per volume or a combination. For example,
- BAC of 0.20% can mean 2 grams of alcohol per 1000 grams of an individual's blood
- Or it can mean 0.2 grams of alcohol per 100 millilitres of blood.
Permissible Blood Alcohol Limits while driving light motor vehicle (e.g. passenger car)
| Blood Alcohol Limits | Countries |
| 0.08% | Mexico, Republic of Ireland, New Zealand, Luxembourg, Malaysia, Malta, the United States, Canada, and the United Kingdom. |
| 0.05% | Argentina, Australia, Austria, Belgium, Bulgaria, Croatia, Denmark, Finland, France, Germany, Greece, Iceland, Israel, Italy, Lithuania, Republic of Macedonia, the Netherlands, Portugal, Serbia, Slovenia, Switzerland, and Turkey. |
| 30 mg/dL | India |
| 25 mg/dl | Spain |
| 20 mg/dL | Norway, Sweden, Russia, Estonia and Poland |
For Pilots: The Federal Aviation Regulations governing U.S. pilots prohibits operation of an aircraft within eight hours of consumption or while having as little as 0.04 percent of alcohol by weight in the blood. Similar laws apply to most of the countries.
Common Carriers such as buses: In the United States operators of carriers such as buses are restricted to a 0.01% limit.
