A BAC chart is the Widmark equation as a lookup table: alcohol in, divided through the water in your body, minus what your liver has cleared since. The version above differs from the ones printed on coasters in two ways. Each cell is an interval rather than a single figure, and the hours control does the subtraction at each edge's own published rate rather than applying one average to everybody.
How to read it
- Find your weight column, then your drink row. The cell is the estimated BAC range at the moment of your last drink, or later if you have moved the hours control.
- Plan around the higher number. The low edge assumes a body that holds alcohol in more water and clears it quickly; the high edge assumes the opposite. Neither is more likely than the other, but only one of them is the cautious reading.
- Peak means everything at once. The zero-hour column assumes every drink has already reached your blood and none has been cleared, which is the arithmetic worst case. Spread the same drinks over an evening and the real peak is lower, which is what the calculator's session field accounts for.
- A cell is not a verdict. Two people in the same cell can be impaired to visibly different degrees, and a number below a legal limit is not a statement that anything is safe.
What each level does to you
Effects by blood alcohol level, described in terms of the faculties that matter for anything demanding: attention, tracking, reaction time, and self-assessment.4 Tolerance changes how much of this you notice, and none of how much of it is happening.
| BAC (%) | What is measurably happening |
|---|---|
| 0.02 | Mood lifts, judgment softens. Measurable already: visual tracking of a moving object declines, and so does the ability to do two things at once. |
| 0.05 | Small-muscle control goes, including focusing your eyes. Alertness, coordination, and response to a sudden emergency are all measurably worse. The legal limit across most of Europe. |
| 0.08 | Balance, speech, vision, reaction time, and hearing are all impaired. Short-term memory and concentration slip, and detecting danger takes longer. The legal limit in the US, Canada, and most of the UK. |
| 0.10 | Clear deterioration in reaction time and control. Slurred speech, poor coordination, slowed thinking that the person themselves rarely notices. |
| 0.15 | Major loss of balance and muscle control; vomiting is common in people without high tolerance. Roughly where a bottle of wine on an empty stomach lands many adults. |
| 0.20 | Disorientation, confusion, nausea. Blackouts, meaning memory that is never recorded rather than forgotten, become likely around here. |
| 0.30 | Stupor, little comprehension of surroundings, loss of consciousness possible. Alcohol poisoning is a real risk from here upward. |
| 0.40+ | Coma and life-threatening depression of breathing and heart rate. A medical emergency in every case. |
The dangerous part of this ladder is the bottom of it. Crash risk is already measurably elevated at levels where nobody feels drunk, and it climbs steeply from there.4
Legal limits for reference
| Limit (BAC %) | Where it applies |
|---|---|
| 0.08 | United States, Canada, England, Wales, Northern Ireland |
| 0.05 | Netherlands, Scotland, Australia, and most of the EU |
| 0.02 | New and professional drivers in much of Europe; Sweden, Norway, Poland |
| 0.00 | Zero tolerance: Czechia, Hungary, Romania, and US drivers under 21 |
Limits vary by country, state, vehicle class, and licence age, so check the one where you actually are. None of them divides impaired from unimpaired: they are the points at which the law stops arguing. If you are reading a row of this chart to work out whether to drive, that question has its own page, and no cell here answers it.
Never drive after drinking. If you are wondering whether you are sober enough to drive, the answer is no.
Why every cell is a range
Two numbers in the Widmark equation are not measurements of you. The distribution ratio, how much of your body is water for alcohol to dissolve into, is published as roughly 0.49 to 0.61 for women and 0.6 to 0.76 for men.3 The elimination rate is published as 0.012 to 0.02 percentage points per hour.2 Both are population intervals, and intervals in means an interval out.
That is why a chart with one number per cell is not a more precise chart, only a quieter one. The spread is real, it is wide enough to cross a legal limit, and the honest thing to do with it is print it. The full method, with every assumption named, sets out where each figure comes from.
What no chart can include: what was actually in the glass, food in your stomach, the 30 to 90 minutes alcohol takes to finish absorbing, medications, liver health, or body composition beyond a sex average. For your own night rather than a row in a table, the BAC calculator takes the drinks you actually had and the times you actually drank them.
Frequently asked questions
What is a BAC chart?
A BAC chart estimates blood alcohol concentration from the number of standard drinks, body weight, and sex, then subtracts the alcohol your liver has cleared since. It is a lookup version of the Widmark equation, the same formula behind every blood alcohol calculator. It estimates; it does not measure, and it cannot account for your stomach, your liver, or what was really in the glass.
How many drinks does it take to reach 0.08?
It depends mostly on body size and sex. For a 60 kg woman, two US standard drinks already straddle 0.08 at the moment of the last drink and three put her clearly above it; a 100 kg man straddles it at four and is clearly above at five. Drinking the same amount over a longer evening lowers the peak, because elimination runs the whole time. There is no drink count that is safe for everyone, which is the main thing a chart teaches once you read across a row.
Is a BAC chart accurate for women?
It is as accurate for women as for men, which is to say approximate, provided it uses the right distribution ratio. Alcohol dissolves in body water, and women carry a lower proportion of water for a given weight, so the same drinks in the same body weight produce a higher BAC. This chart uses published ranges of about 0.49 to 0.61 for women and 0.60 to 0.76 for men rather than a single average for everyone.
How much does BAC drop per hour?
About 0.015 percentage points per hour on average, with a published range across healthy adults of roughly 0.012 to 0.020. That is close to one US standard drink an hour. The rate is set by liver enzymes working at capacity, so it does not speed up for coffee, food, water, exercise, or a cold shower, and it barely varies with how much you want it to.
What is a normal blood alcohol level?
Zero. The body produces only trace amounts of alcohol on its own, so any measurable blood alcohol level came from drinking. Legal limits of 0.05 or 0.08 are prosecution thresholds rather than normal or safe values, and measurable impairment of reaction time and judgment begins around 0.02, below every limit in the world.
What BAC level is dangerous?
Risk rises continuously, but 0.30 and above is the range where stupor, loss of consciousness, and alcohol poisoning cluster, and 0.40 is frequently fatal. Those numbers are reachable on an ordinary heavy night for a small person drinking quickly. Anyone who is confused, breathing slowly, cold and clammy, or cannot be woken needs emergency services, not a chart: 911 in the US, 112 in Europe.
Does eating change the numbers in this chart?
It changes when you reach them, and lowers the peak you reach. Food in the stomach slows how fast alcohol crosses into the blood, so the same drinks spread over a longer absorption produce a lower maximum, sometimes substantially lower. What food does not change is the total your liver has to clear, so the time back to zero is largely unaffected. The chart assumes the worst case of everything absorbed at once, which is why a fed drinker usually lands under the cell they read.
Why does the chart use body weight rather than BMI?
Because alcohol dissolves in body water, and weight combined with a sex-based distribution ratio is what the Widmark equation was built on. BMI adds height into a ratio that says nothing directly about body water, so it would not improve the estimate. The real limitation is body composition: two people at the same weight with very different proportions of muscle and fat hold different amounts of water, and the chart cannot see that. Very lean and very heavy bodies sit outside the assumption in opposite directions.
Does body weight change your alcohol tolerance?
It changes your blood alcohol, which is not the same as tolerance. A heavier body dilutes the same drinks into more water, so the same alcohol produces a lower BAC, which the columns of this chart show directly. Tolerance is a separate thing: how much impairment a given BAC produces in a habitual drinker versus an occasional one. Tolerance changes what you feel; weight changes the number. Neither changes how fast the alcohol clears.
Why does every cell show a range instead of one number?
Because the formula behind it needs two constants that differ from person to person, and the research reports both as intervals rather than values. A chart printing 0.079 in a cell has not measured anything more precisely; it has picked the middle of an interval and hidden the rest. The width of each range here is the honest uncertainty, and the high edge is the one to plan around.
Can I use a BAC chart to decide whether to drive?
No. A chart cannot measure your blood, its ranges straddle the legal limit for most realistic nights, and impairment is measurable well below every legal limit. Never drive after drinking. If you are wondering whether you are sober enough to drive, the answer is no.
Related tools and answers
Your own drinks and times instead of a row: a BAC range for right now, with the decay curve.
Am I still drunk?The morning-after question: when your BAC likely reaches zero, in clock times.
What does BAC stand for?The notation, promille conversion, and what the levels mean in plain terms.
Standard drink calculatorThe chart counts in standard drinks. Convert a real pour into them here.
Am I too drunk to drive?The one page here whose answer is not an estimate.
How accurate are BAC calculators?Each source of error, sized — and the one that beats the formula itself.
How these estimates workThe Widmark formula, the published ranges, and every error source, cited.
How to sober upWhy nothing moves a number on this chart except time.
Sources
- NIAAA. What is a standard drink?
- Jones, A.W. (2010). Evidence-based survey of the elimination rates of ethanol from blood. Forensic Science International.
- Norberg, Å. et al. (2003). Role of variability in explaining ethanol pharmacokinetics. Clinical Pharmacokinetics.
- NHTSA. Drunk driving: how alcohol affects driving ability.
- NIAAA. Understanding the dangers of alcohol overdose.
- StatPearls. Ethanol toxicity. NCBI Bookshelf.