What does BAC stand for?
BAC stands for blood alcohol concentration: the fraction of your blood that is alcohol. In the US it is written as a percentage by weight, so a BAC of 0.08 means 0.08 grams of alcohol in every 100 milliliters of blood. Small number, large consequences: at one part in 1,250, your reaction time, judgment, and coordination are all measurably impaired.
How BAC is written around the world
The US convention is percent: 0.08% by weight. Continental Europe uses promille, grams per liter of blood, which is ten times the US number: the Dutch limit of 0.5 promille is 0.05 in US notation. The UK writes milligrams per 100 milliliters: the 80 mg limit is again 0.08. Same blood, three notations.
What different BAC levels feel like
| BAC (%) | Typical effects |
|---|---|
| 0.02 | Mild relaxation, slightly altered mood. Judgment already begins to soften. |
| 0.05 | Lowered inhibition, impaired coordination and tracking. The legal driving limit in the Netherlands and much of Europe. |
| 0.08 | Clear impairment of reaction time, self-assessment, and muscle control. The legal driving limit in most of the US and the UK. |
| 0.15 | Major loss of balance and control; vomiting common. Roughly a bottle of wine on an empty stomach for many adults. |
| 0.30+ | Stupor, blackout territory, risk of losing consciousness. Medical danger zone; alcohol poisoning deaths cluster here and above. |
Ranges blur with tolerance: regular drinkers feel less at the same BAC while being just as impaired on reaction-time tests. Legal limits are prosecution thresholds, not safety ratings.
Never drive after drinking. If you are wondering whether you are sober enough to drive, the answer is no.
Estimate yours
Two tools on this site work in BAC terms. The sober-up estimator turns last night into a window for when your BAC likely reaches zero, and the standard drink calculator converts any pour into the drink counts the math runs on. Both show ranges, never point values, because the underlying formula has a substantial margin of error.
Frequently asked questions
What does BAC stand for?
BAC stands for blood alcohol concentration, sometimes read as blood alcohol content. It is the fraction of your blood that is alcohol, usually written as a percentage by weight: a BAC of 0.08 means 0.08 grams of alcohol per 100 milliliters of blood, or about one part in 1,250.
What is the legal BAC limit for driving?
In most of the United States and the UK the limit is 0.08 percent; in the Netherlands and much of Europe it is 0.05, with 0.02 for new drivers; several countries use zero. A limit is a prosecution threshold, not a safety rating: impairment of judgment and reaction time is measurable well below every one of these numbers.
How is BAC measured?
Directly, only through blood analysis. Breathalyzers estimate it from deep-lung air using a known blood-to-breath ratio, which is accurate enough for law enforcement devices and decent consumer fuel-cell units. Calculators, including ours, do not measure anything: they estimate from population averages and honest ones say so.
What BAC counts as drunk?
Legally, many US states define intoxication at 0.08. Physiologically there is no bright line: measurable impairment starts around 0.02 to 0.05, well below the point where most people feel drunk. Feeling sober is one of the first casualties of drinking, which is why self-assessment fails.
Is BAC the same as promille?
Same measurement, different unit. Promille, used across continental Europe, is grams of alcohol per liter of blood, exactly ten times the US percentage figure: a Dutch 0.5 promille limit equals a US-style BAC of 0.05 percent.