How fast alcohol leaves the blood
The liver breaks down most alcohol, at a fairly steady amount per hour. A review of the published measurements puts the average for moderate drinkers at 15 mg per 100 ml of blood an hour, which is 0.015% BAC an hour, with a range of 10 to 35 mg between people. Heavy drinkers clear it faster: about 19 mg an hour in drivers arrested for drink driving, many of them binge or heavy drinkers, and 25 to 35 mg an hour in people in alcohol detox (Jones, 2010).
Because the same amount comes off each hour, a level twice as high takes twice as long to clear:
| Blood alcohol | Time to zero at 0.015% an hour |
|---|---|
| 0.02% | 1 h 20 min |
| 0.05% | 3 h 20 min |
| 0.08% | 5 h 20 min |
| 0.10% | 6 h 40 min |
| 0.15% | 10 h |
| 0.20% | 13 h 20 min |
Why BAC keeps rising after the last drink
Alcohol in the stomach and intestine continues to enter the bloodstream, so BAC can keep rising even after a person stops drinking (NIAAA). The WaterChamp model spreads each drink evenly over 45 minutes, so its peak comes about 45 minutes after the last drink.
How much alcohol is in a drink
In the US, one standard drink holds about 14 g of pure alcohol: a 12 oz beer at 5%, a 5 oz glass of wine at 12% or a 1.5 oz shot of spirits at 40% (NIAAA). Many real servings are bigger. These are the drinks in the app, with their default serving:
| Drink | Serving | Strength | Alcohol | US standard drinks |
|---|---|---|---|---|
| Long Island Iced Tea | 300 ml (10.1 fl oz) | 16% | 38 g | 2.7 |
| Margarita | 240 ml (8.1 fl oz) | 13% | 25 g | 1.8 |
| Beer | 500 ml (16.9 fl oz) | 5% | 20 g | 1.4 |
| Cosmopolitan | 120 ml (4.1 fl oz) | 20% | 19 g | 1.4 |
| Espresso Martini | 120 ml (4.1 fl oz) | 20% | 19 g | 1.4 |
| Irish Coffee | 240 ml (8.1 fl oz) | 10% | 19 g | 1.4 |
| Mojito | 240 ml (8.1 fl oz) | 10% | 19 g | 1.4 |
| Cider | 500 ml (16.9 fl oz) | 4.5% | 18 g | 1.3 |
| Martini | 90 ml (3 fl oz) | 25% | 18 g | 1.3 |
| Gin & Tonic | 200 ml (6.8 fl oz) | 10% | 16 g | 1.1 |
| Mulled Wine | 200 ml (6.8 fl oz) | 10% | 16 g | 1.1 |
| Raki | 45 ml (1.5 fl oz) | 45% | 16 g | 1.1 |
| Red Wine | 150 ml (5.1 fl oz) | 13.5% | 16 g | 1.1 |
| Rum & Coke | 180 ml (6.1 fl oz) | 11% | 16 g | 1.1 |
| White Wine | 150 ml (5.1 fl oz) | 12.5% | 15 g | 1.1 |
| Bloody Mary | 150 ml (5.1 fl oz) | 12% | 14 g | 1.0 |
| Brandy | 45 ml (1.5 fl oz) | 40% | 14 g | 1.0 |
| Champagne | 150 ml (5.1 fl oz) | 12% | 14 g | 1.0 |
| Gin | 45 ml (1.5 fl oz) | 40% | 14 g | 1.0 |
| Hard Seltzer | 355 ml (12 fl oz) | 5% | 14 g | 1.0 |
| Hugo | 250 ml (8.5 fl oz) | 7% | 14 g | 1.0 |
| Rosé Wine | 150 ml (5.1 fl oz) | 12% | 14 g | 1.0 |
| Rum | 45 ml (1.5 fl oz) | 40% | 14 g | 1.0 |
| Sangria | 200 ml (6.8 fl oz) | 9% | 14 g | 1.0 |
| Spirit | 45 ml (1.5 fl oz) | 40% | 14 g | 1.0 |
| Vodka | 45 ml (1.5 fl oz) | 40% | 14 g | 1.0 |
| Whiskey | 45 ml (1.5 fl oz) | 40% | 14 g | 1.0 |
| Aperol Spritz | 200 ml (6.8 fl oz) | 8% | 13 g | 0.9 |
| Prosecco | 125 ml (4.2 fl oz) | 11% | 11 g | 0.8 |
| Radler | 500 ml (16.9 fl oz) | 2.5% | 10 g | 0.7 |
| Vermouth | 75 ml (2.5 fl oz) | 16% | 9 g | 0.6 |
| Mimosa | 150 ml (5.1 fl oz) | 6% | 7 g | 0.5 |
A 500 ml beer at 5% is 1.4 standard drinks, a 150 ml glass of red wine is 1.1, and a Long Island Iced Tea is 2.7.
What one drink does to BAC
The Widmark formula divides the alcohol by body weight and by a factor that is smaller for women, so the same drink gives a lighter person a higher BAC, and a woman a higher BAC than a man of the same weight (Reiter, 2020). In the BAC calculator, one 500 ml beer at 5% (20 g of alcohol) peaks near 0.03% for a 70 kg man and is gone about 2 hours 45 minutes after he starts it. For a 60 kg woman, the same beer peaks near 0.05% and takes about 4 hours.
Coffee and cold showers do not speed it up
Only time lowers blood alcohol, because the liver clears it at its own rate (Jones, 2010). NIAAA warns that cold showers, hot coffee and walking do not reverse the effects of alcohol overdose (NIAAA).
How long alcohol shows up on tests
Alcohol itself can be measured in blood, urine and sweat for only a few hours after drinking. Its breakdown products, such as ethyl glucuronide, fatty acid ethyl esters and phosphatidylethanol, can in some cases be found over a much wider window, in hair for example (Cabarcos, 2015).
Estimate your own evening
The BAC calculator works out your blood alcohol through an evening from your drinks, weight and sex, and the time it reaches zero. Each drink absorbs over 45 minutes, and the level falls by 0.015% an hour. It is an estimate. Never use it to decide whether to drive.
Questions
How long does it take for a BAC of 0.08% to reach zero?
About 5 hours 20 minutes at the average rate of 0.015% an hour. At the slow end of the range, 0.010% an hour, it takes 8 hours.
How long does one beer last?
For a 70 kg man, a 500 ml beer at 5% is gone about 2 hours 45 minutes after he starts it. For a 60 kg woman, it takes about 4 hours.
Does coffee sober you up?
No. Only time lowers blood alcohol, and NIAAA warns that hot coffee, cold showers and walking do not reverse alcohol overdose.
Why is my BAC still rising after I stopped drinking?
Alcohol still in the stomach and intestine keeps entering the blood for a while, so the level can rise after the last drink (NIAAA).
