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The body clears roughly one unit per hour, but this varies hugely with size, sex, food, liver and luck: nothing speeds it up, not coffee, showers or sleep. This is a rough educational guide, NOT a fitness-to-drive test: if in any doubt, do not drive. Morning-after drink-driving convictions are common and carry the same penalties.
What The Sober Time Calculator Works Out
- Units drunk: a pint of ordinary-strength lager or cider counts as 2.3 units, a large 250 ml glass of wine 3.3 and a single spirit measure 1. Craft-strength cans carry more, and the doubles-and-large-pours drift of home measures is where nights get underestimated.
- Rough time to zero: the liver clears roughly one unit an hour once it gets to work, so the estimate is units plus an hour's grace for absorption, rounded up. Four pints is nine-odd units and a system still processing at breakfast. No lever accelerates it: coffee, cold showers, fry-ups and sleep all produce a more alert drunk person rather than a sober one.
- Example: what an 11pm last drink means for the next morning. The one-unit-per-hour figure is an average across bodies that vary widely, which is why every honest calculator says "at least" and means it.
- Extra drinks (advanced): strong 440 ml cans (about 2.5 units), double spirits (2 units) and bottles of wine (nearly 10 units each, or a quarter bottle at a time) so a mixed night is counted properly.
- Strength of your pints (advanced): units per pint are 568 x ABV / 1,000, so a 5.2% lager is 3 units a pint against 2.3 for a 4% session beer. Six pints of the strong stuff is 18 units and most of a day to clear.
- Clearance rate and absorption (advanced): the two assumptions behind the sum. Smaller people, women and anyone drinking on an empty stomach often clear nearer 0.8 units an hour, and a late meal can push peak absorption back by an hour or more. The slow-clearer card shows the 0.8 figure for comparison.
- Time of your last drink and driving time (advanced): a clock time for when alcohol may finally be gone, and the margin (or shortfall) before you need to drive. A margin under two hours is thin given the variation; the hour-by-hour table shows roughly how many units remain through the night and morning.
- Against the weekly guideline (advanced): the session as a share of the UK low-risk guideline of 14 units a week spread over three or more days. One big night can exceed the whole week.
- Caveats: blood alcohol depends on weight, sex, food and timing, and the legal limits differ by nation (Scotland's is lower than England and Wales's), so no units-in calculator can clear anyone to drive: the only safe morning-after number is zero plus a margin. Morning-after convictions carry the same penalties and criminal record, and every taxi costs less than a ban. If drinking itself is the worry rather than the timing, NHS alcohol support and Drinkaware's tools are the doors worth knowing; this page does arithmetic, not permission.
Further reading: Drinkaware.