Editing Blood alcohol content (section)

== Units of measurement ==

BAC is generally defined as a fraction of weight of alcohol per volume of blood, with an [[SI coherent derived unit]] of [[Kilogram per cubic metre|kg/m<sup>3</sup>]] or equivalently grams per liter (g/L). Countries differ in how this quantity is normally expressed. Common formats are listed in the table below. For example, the US and many international publications present BAC as a percentage, such as 0.05%. This would be interpreted as 0.05 grams per deciliter of blood. This same concentration could be expressed as 0.5‰ or 50&nbsp;mg% in other countries.<ref>{{cite web |title=BAC Formats |url=http://www.mecinca.net/ALCOHOLIMETROS_Alcosim/BAC%20BrAC%20conversion%20table[1].pdf |access-date=3 November 2023}}</ref>

{| class="wikitable" style="margin: 1em auto 1em auto"
! Sign !! Units !! Used in
|-
| 1 percent (%), 1 g%<ref name="Jones2011" /> || {{val|1|u=g/dL}} = {{val|1|u=cg/mL}} = {{val|10|u=g/L}} = 1 g/100 mL || US, Australia,<ref name="Jones2011" /><ref>{{Cite web |date=8 February 2022 |orig-date=Original date 14 February 2017 |title=Blood alcohol levels |url=https://adf.org.au/insights/blood-alcohol-levels/ |website=Alcohol and Drug Foundation (Australia)}}</ref> Canada<ref>{{Cite web |date=n.d. |title=Blood Alcohol Concentration (BAC) |url=https://madd.ca/pages/impaired-driving/overview/blood-alcohol-concentration-bac/ |access-date=21 July 2022 |website=Mothers Against Drunk Driving (MADD Canada)}}</ref>
|-
| 1 [[per mille]] (‰){{efn|In Germany, Finland, Netherlands and Sweden, the local language term ''[[per mille|promille]]'' is used; this is occasionally provided as a courtesy in English texts.<ref name="HRB BAL">{{cite web |title=Blood alcohol level (BAL) |publisher=Health Research Board (Ireland) |url=https://www.drugsandalcohol.ie/glossary/info/blood_alcohol_level }}</ref>}}   || {{val|1|u=g/L}} = {{val|1|u=mg/mL}} = 100 mg/1 dL || Austria,<ref name="Jones2011" /> Belgium,<ref name="Jones2011" /> Bulgaria,{{cn|date=November 2023}} Czech Republic,{{cn|date=November 2023}} Denmark,{{cn|date=November 2023}} France,<ref name="Jones2011" /> Germany,<ref name="Jones2011" /> Latvia,{{cn|date=November 2023}} Lithuania,{{cn|date=November 2023}} Netherlands,<ref>{{Cite web|url=http://wetten.overheid.nl/jci1.3:c:BWBR0006622&hoofdstuk=II&paragraaf=1&artikel=8&lid=2|title=artikel 8, tweede lid, van de Wegenverkeerswet 1994|date=21 February 2025}}</ref><ref>{{Cite web|url=https://www.rijksoverheid.nl/onderwerpen/verkeersveiligheid/vraag-en-antwoord/mag-ik-met-alcohol-op-deelnemen-aan-het-verkeer|title=Met hoeveel alcohol mag ik deelnemen aan het verkeer?|date=21 February 2025}}</ref> Poland,<ref>{{Cite journal |date=2019-10-15 |title=Nietrzeźwość a ryzyko zgonu w wypadku komunikacyjnym = Insobriety and the risk of death in traffic accident {{!}} Journal of Education, Health and Sport |url=https://apcz.umk.pl/JEHS/article/view/2761 |journal=Journal of Education, Health and Sport | volume=5 | issue=6 | pages=419–432 |language=pl | last1=Lasota | first1=Dorota | last2=Staniszewska | first2=Anna | last3=Tarchalska-Kryńska | first3=Bożena | last4=Mirowska-Guzel | first4=Dagmara | last5=Krajewski | first5=Paweł }}</ref> Portugal,{{cn|date=November 2023}} Romania,{{cn|date=November 2023}} Russia,{{cn|date=November 2023}} Slovenia,{{cn|date=November 2023}} Spain,<ref name="Jones2011" /> Sweden,{{cn|date=November 2023}} Switzerland,{{cn|date=November 2023}} Turkey,{{cn|date=November 2023}} Norway{{cn|date= April 2025}}
|-
| 1 [[Milligram per cent|mg%]]<ref name="Jones2011" /> || {{val|1|u=mg/dL}} = {{val|0.01|u=g/L}} = 1 mg/100 mL || United Kingdom<ref>{{cite web |title=The drink drive limit |url=https://www.gov.uk/drink-drive-limit |access-date=3 November 2023 |website=GOV.UK |language=en}}</ref> Ireland, Canada, New Zealand<ref name="Jones2011" />
|}

It is also possible to use other units. For example, in the 1930s Widmark measured alcohol and blood by mass, and thus reported his concentrations in units of g/kg or mg/g, weight alcohol per weight blood. Blood is denser than water and 1 mL of blood has a mass of approximately 1.055 grams, thus a mass-volume BAC of 1 g/L corresponds to a mass-mass BAC of 0.948 mg/g. Sweden, Denmark, Norway, Finland, Germany, and Switzerland use mass-mass concentrations in their laws,<ref name="Jones2011" /> but this distinction is often skipped over in public materials,<ref>{{cite web |title=Drink-driving: What are the rules? |url=https://www.ch.ch/en/vehicles-and-traffic/how-to-behave-in-road-traffic/traffic-regulations/alcohol-in-road-traffic-and-navigation/#how-much-wine-or-beer-can-i-drink |website=www.ch.ch |language=en}}</ref> implicitly assuming that 1 L of blood weighs 1 kg.<ref>{{cite news |last1=Nager |first1=Anna |title=Alkoholpromille, beräkning|trans-title=Calculation of alcohol per mille |url=https://www.netdoktor.se/psykiatri/missbruk-beroende/sjukdomar/alkoholpromille-berakning/ |access-date=13 April 2024 |work=Netdoktor |date=4 May 2020 |language=sv-SE|quote=I detta sammanhang räknar man med att 1 liter blod väger 1 kilo.|trans-quote=In this context, it is assumed that 1 liter of blood weighs 1 kilogram.}}</ref>

In [[pharmacokinetics]], it is common to use the [[amount of substance]], in [[Mole (unit)|mole]]s, to quantify the dose. As the [[molar mass]] of ethanol is 46.07 g/mol, a BAC of 1 g/L is 21.706 mmol/L (21.706 mM).<ref>{{cite web |title=Ethanol |url=https://pubchem.ncbi.nlm.nih.gov/compound/Ethanol |access-date=3 November 2023 |website=pubchem.ncbi.nlm.nih.gov |language=en}}</ref>