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Enter how many units you drank and your wake time — see when alcohol clears your system, how much it will disrupt your sleep tonight, and what time to stop next time.
Is alcohol the only thing affecting your sleep?
Alcohol is one of 17 causes our AI analyses. Take the quiz to find out what else is draining your energy.
Take the fatigue quiz →Alcohol is a sedative, which is why it makes falling asleep easier. But it has the opposite effect on sleep quality. As your body metabolises alcohol through the night, it triggers a rebound activation of the nervous system — particularly in the second half of sleep — which reduces REM sleep, increases wakefulness, and causes you to wake earlier than you otherwise would.
The body processes alcohol at roughly one unit per hour. This calculator uses your unit intake and bedtime to estimate when alcohol will clear your system and how significantly it will affect the architecture of your sleep that night.
The liver processes roughly one unit of alcohol per hour for most adults — though this varies with body weight, sex, liver health, and whether you have eaten. A large glass of wine (2.3 units) takes approximately 2–3 hours to clear. Four pints of beer (9+ units) may still be present 9–10 hours later, well into the following morning.
For minimal sleep disruption, alcohol should ideally be cleared before you go to bed. If you are sleeping at 11pm, stopping at 8–9pm for light drinking (1–2 units) gives enough clearance time. For heavier nights, the sleep disruption is difficult to avoid entirely — the calculator shows what to expect based on your specific intake.
As alcohol is metabolised, the sedative effect wears off and the nervous system rebounds — becoming more active than it would be normally. This typically happens in the early hours of the morning, causing lighter sleep, more waking, and often an earlier rise than intended. This is the rebound effect, and it is why alcohol-aided sleep rarely feels restorative.