Blood Alcohol Elimination Calculator
Estimate how many UK alcohol units may still be left to process after drinking, using drink size, ABV, time since the last drink and a clear non-driving safety warning.
Enter The Drinking Details
Estimated Units Left To Process
About 1.7 more processing hours at 1 unit per hour, before any extra planning buffer.
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What This Calculator Can And Cannot Do
This calculator estimates remaining UK alcohol units to process from drink volume, ABV and time since the final drink. It is for planning a cautious wait, checking a unit total, or seeing why a late night can still matter the next morning. It is not a blood alcohol concentration calculator. It does not estimate breath alcohol, urine alcohol, impairment, hangover risk, legal compliance, fitness for work, ability to drive, ability to care for children or medical safety.
The wording matters because the same unit total can affect people differently. Body size, sex, food, sleep, medicines, illness, liver health, drinking speed and tolerance can all alter how alcohol affects a person. GOV.UK states that legal drink-drive limits are strict, but it is impossible to say exactly how many drinks this equals because it differs for each person. The safest practical rule for driving is not to drink at all when you plan to drive, and this calculator does not replace that rule.
Alcohol Unit Formula
The UK unit formula uses drink volume in millilitres and ABV percentage. NHS guidance defines one unit as 10 ml or 8 g of pure alcohol and says this is around the amount an average adult can process in one hour.
Units in one drink = volume ml x ABV / 1,000
Total units = units per drink x servings + extra units
Estimated units left = total units - ((hours since last drink - absorption delay) x processing rate)
Negative values are shown as zero remaining units. The optional buffer is shown separately, because extra time is a planning choice rather than proof of sobriety.
Why The Result Is About Units, Not A BAC Number
Blood alcohol concentration depends on how alcohol is absorbed, distributed and eliminated in a person’s body. A unit count is much simpler: it says how much pure alcohol was in the drinks. The calculator therefore gives a unit-processing estimate. That makes the arithmetic transparent, but it also sets a hard boundary. It cannot convert the result into a breathalyser reading or tell whether someone is below a legal limit.
Do not try to adjust the result with coffee, water, cold showers, food or sleep. Those may change comfort, hydration or alertness, but they do not give a reliable way to clear alcohol faster. Time is the part the calculator can model; personal impairment is not.
Worked Examples
Two 568 ml pints at 5% are about 5.68 units. If the last drink ended four hours ago and a one-hour delay is used, the calculator counts about three processing hours and shows about 2.68 units left.
A 750 ml bottle at 13.5% contains about 10.1 units, so half is about 5.1 units. With seven hours since the last drink and a one-hour delay, the arithmetic estimate may be near zero at one unit per hour, but that is still not a driving decision.
Three 50 ml doubles at 40% ABV are 6 units. If they were drunk late and only two hours have passed since the last drink, very little processing time may have elapsed after the delay.
UK Drink-Drive Limits Are Not Used In The Calculation
The calculator includes a regional note because many people arrive here after searching for morning-after driving questions. The note is deliberately separate from the result. Legal limits are measured by alcohol concentration in blood, breath or urine. This page estimates remaining alcohol units to process, which is not the same thing.
| Part Of The UK | Blood Limit | Breath Limit | Urine Limit |
|---|---|---|---|
| England, Wales And Northern Ireland | 80 mg alcohol per 100 ml blood | 35 micrograms alcohol per 100 ml breath | 107 mg alcohol per 100 ml urine |
| Scotland | 50 mg alcohol per 100 ml blood | 22 micrograms alcohol per 100 ml breath | 67 mg alcohol per 100 ml urine |
Common UK Drink Unit Checks
| Drink | Calculation | Approximate Units | Use In The Calculator |
|---|---|---|---|
| Single 25 ml spirit at 40% | 25 x 40 / 1,000 | 1.0 unit | Set serving volume to 25 ml, ABV 40, servings 1. |
| Double 50 ml spirit at 40% | 50 x 40 / 1,000 | 2.0 units | Set serving volume to 50 ml, ABV 40. |
| 330 ml beer at 5% | 330 x 5 / 1,000 | 1.65 units | Useful for cans and bottles. |
| 568 ml pint at 4% | 568 x 4 / 1,000 | 2.27 units | Use the actual ABV from the pump clip if known. |
| 175 ml wine at 13.5% | 175 x 13.5 / 1,000 | 2.36 units | Common restaurant glass size. |
| 750 ml wine bottle at 13.5% | 750 x 13.5 / 1,000 | 10.13 units | Use servings as your share of the bottle. |
Morning-After Planning Notes
The morning after drinking is where people often undercount. They may remember leaving the bar but not the final drink, the ABV, the size of home pours or the time food was eaten. Strong lager, large wine glasses and double spirits add units quickly. If the inputs are uncertain, run a higher-units case and a slower processing-rate case. If either still shows units left, treat the timing as unresolved.
Even if the arithmetic reaches zero, sleep loss, dehydration, medication, illness and hangover symptoms can still make driving, machinery or caring tasks unsafe. A calculator can show why more time may be needed, but it cannot grant permission.
When To Get Help Instead Of Calculating
- Call 999 or seek emergency help if someone is unconscious, breathing abnormally, having a seizure, has blue or pale skin, cannot be woken, or may have poisoning.
- Use NHS 111 or local urgent care advice if you are worried about symptoms after drinking but it is not an immediate emergency.
- Speak to a GP, pharmacist or alcohol support service if cutting down causes shaking, sweating, anxiety, vomiting or other withdrawal symptoms.
- Do not stop heavy daily drinking suddenly without medical advice, because alcohol withdrawal can be dangerous.
Step-By-Step Use
Use volume, ABV and servings for the main drink. Add extra units for other drinks if you know them. If pours were larger than standard, increase the serving volume.
Enter hours since the final drink ended. Keep the absorption delay if the final drink was recent or taken with food over a long evening.
Use the result as an arithmetic estimate only. If the question is driving, medicine, work, childcare or symptoms, use official, medical or employer guidance instead.
FAQ
Can this calculator tell me when I can drive?
No. It cannot measure BAC, breath alcohol, impairment or legal status. GOV.UK states that the number of drinks that puts someone over the limit differs by person.
Why use one unit per hour?
NHS alcohol-unit guidance says one unit is around the amount an average adult can process in an hour. This is a rough planning rate, not a personal measurement.
Should time count from the first drink or last drink?
This calculator uses time since the final drink and an absorption delay. That is a cautious way to avoid treating a recent final drink as already processed.
Does food, water or coffee speed up alcohol elimination?
No reliable amount for faster elimination is added here. Food can affect absorption and comfort, but time is still the key factor used in the estimate.
What if I only know the number of units?
Use the Known Units preset, put the known amount in Extra Units, and set the main serving count to zero. The result will still estimate units left from timing and rate.
Why is Scotland shown separately?
Scotland has lower legal drink-drive limits than England, Wales and Northern Ireland. The calculator displays the official limits as a note, but does not compare your estimate with them.
Sources
- NHS. (2024). Alcohol Units. NHS. https://www.nhs.uk/live-well/alcohol-advice/calculating-alcohol-units/
- GOV.UK. (n.d.). The Drink Drive Limit. GOV.UK. https://www.gov.uk/drink-drive-limit
- GOV.UK. (n.d.). Drink-Driving Penalties. GOV.UK. https://www.gov.uk/drink-driving-penalties
- Scottish Government. (2018). Drink-Drive Limit: Policy. Scottish Government. https://www.gov.scot/publications/drink-drive-limit-policy/
- NHS. (2025). Poisoning. NHS. https://www.nhs.uk/conditions/poisoning/