Many methods of expressing blood alcohol concentration are in use throughout the world and converting from one to another can be quite confusing. Check with the regulating agency for your testing program to determine what specific unit of measure is used in your jurisdiction.
One jurisdiction may express a concentration of 80 milligrams (mg) of alcohol in 100 mL of blood as 80mg%. Since 80 mg is 0.08 grams, 0.08 grams of alcohol in 100 mL may be written as 0.08%. In other words, 80 mg% is equal to 0.08% which is equal to 80 mg/dL (deciliter = 100 mL). This value can also be described as 0.08 BAC. In the UK the same concentration is expressed as 34.78 ug/100mL.
Even within the United States, various units may be used. You may see results expressed in blood units (grams/100mL of blood or milligrams/dL of blood) or as breath units (grams/210L of breath).