Breath alcohol testing is a common method of determining the level of alcohol in a person’s blood. Breath alcohol testing devices, also known as breathalyzers, measure the amount of alcohol in a person’s breath and convert it to an equivalent amount of alcohol in their blood. This conversion is based on a ratio that relates the concentration of alcohol in breath to the concentration of alcohol in blood. This ratio is known as the blood/breath alcohol ratio (BBR) or the partition ratio.


However, the BBR is not a fixed value and can vary depending on various factors, such as temperature, humidity, body composition, health conditions, and individual differences. Therefore, there is no universal BBR that can be applied to all people and situations. Different countries have adopted different BBR values for their legal purposes, which means that the same breath alcohol reading can correspond to different blood alcohol levels in different jurisdictions.


The following table summarizes some of the BBR values and legal breath alcohol limits for different countries, based on various sources. The table also shows the equivalent blood alcohol levels for each breath alcohol limit, using the respective BBR values.


Country BBR Legal breath alcohol limit (mg/L) Equivalent blood alcohol limit (mg/100mL)
UK 2300 35 (England & Wales),

22 (Scotland)

80 (England & Wales),

50 (Scotland)

USA 2100 80 (most states) 80 (most states)
France 2000 25 50
Germany 2100 25 50
Australia 2100 50 50
Canada 2100 80 80
Japan 2100 15 30
China 2100 20 40
India 2300 30 70