Scottish Drink Drive Limit Calculator
Estimate your blood alcohol concentration in mg/100ml and breath µg/100ml calibrated to Scotland's 50 mg/100ml statutory threshold (SSI 2014/328).
Alcohol Logged
Add a drink to see your estimate.
Select a quick preset above or tap "+ Add Drink" to estimate blood alcohol concentration, Scottish / E&W threshold status, and clearance timeline.
Enter drinks above to calculate estimated blood alcohol content.
Impairment persists below the legal limit.
Conservative estimate based on slow elimination metabolism.
Clearance varies by liver enzyme efficiency. Conservative projection accounts for slower metabolic elimination.
View tabular timeline data (Accessible Table Alternative)
| Time | Typical BAC | Low Est. | High Est. |
|---|
At baseline levels, no cognitive or motor impairment is observed.
How the Scottish Drink Drive Limit Calculator Works
Our scottish drink drive limit calculator estimates your blood alcohol concentration using pharmacokinetic distribution principles tailored to Scottish law. By evaluating pure alcohol mass (8 grams per UK unit), gastric absorption timing, and continuous zero-order liver elimination (0.015% / ~15 mg/100ml per hour median), our tool models when your alcohol reading is projected to fall below Scotland's 50 mg/100ml statutory threshold.
Unlike arbitrary single-figure estimators, our system presents realistic metabolic boundaries: from conservative slow elimination (10 mg/100ml per hour) to typical clearance (15 mg/100ml per hour). This allows motorists to evaluate morning-after alcohol clearance with genuine biological margins.
Scotland vs England & Wales Statutory Thresholds
Official statutory thresholds codified under Scottish Statutory Instrument 2014 No. 328 and the UK Road Traffic Act 1988:
| Jurisdiction | Blood (mg/100ml) | Breath (µg/100ml) | Urine (mg/100ml) | Statutory Basis |
|---|---|---|---|---|
| Scotland (Current Law)Enacted 5 Dec 2014 | 50 mg | 22 µg | 67 mg | SSI 2014/328 |
| England, Wales & Northern IrelandHighest limit in Europe | 80 mg | 35 µg | 107 mg | RTA 1988 s.11(2) |
Why Scotland Lowered the Limit in 2014
On 5 December 2014, the Scottish Parliament unanimously passed The Road Traffic Act 1988 (Prescribed Limit) (Scotland) Regulations 2014 (SSI 2014/328), reducing the prescribed blood alcohol limit from 80 mg to 50 mg per 100 ml of blood. This brought Scotland into alignment with the majority of continental European nations and the European Transport Safety Council (ETSC) recommendations.
Crucially for motorists traveling across the Anglo-Scottish border: driving into Scotland immediately subjects you to the lower 50 mg threshold. A reading that would not trigger a per se charge in Northumberland or Cumbria constitutes an immediate criminal offense north of the border.
Official Legislation Repository
To review the codified statutory instrument directly from the UK National Archives, access the official legislation portal below:
Frequently Asked Questions: Scottish Drink Drive Limits
What is the statutory Scottish drink drive limit?
In Scotland, the prescribed legal limit is 50 mg of alcohol per 100 ml of blood (or 22 µg of alcohol per 100 ml of breath, and 67 mg per 100 ml of urine). This threshold was established under Scottish Statutory Instrument 2014 No. 328 (SSI 2014/328), which came into force on 5 December 2014.
How does the Scottish drink drive limit compare to England and Wales?
Scotland enforces a substantially lower threshold (50 mg/100ml blood, 22 µg/100ml breath) than England, Wales, and Northern Ireland (80 mg/100ml blood, 35 µg/100ml breath). A single pint of higher-strength beer or large glass of wine can easily place an adult above the Scottish threshold while remaining below the English limit.
How many drinks can you have before exceeding the Scottish limit?
There is no set drink count. Because blood alcohol concentration depends on body weight, biological sex, metabolism, and food consumption, even a single standard drink can take some individuals over the 50 mg/100ml limit. Police Scotland and road safety campaigns advise that the only reliable limit is zero drinks.
Can I be convicted of drink-driving in Scotland if my BAC is below 50 mg/100ml?
Yes. Under Section 4 of the Road Traffic Act 1988, driving while unfit through drink is an offence regardless of chemical test readings. If a driver's motor coordination or reaction time is impaired by alcohol, they can be prosecuted even if their reading is below 50 mg/100ml.
Where can I read the official Scottish Statutory Instrument?
The regulations are officially published by the National Archives as The Road Traffic Act 1988 (Prescribed Limit) (Scotland) Regulations 2014 (SSI 2014/328), accessible on legislation.gov.uk.
Statutory & Regulatory Citations
Scottish statutory limit referenced from SSI 2014/328 (The Road Traffic Act 1988 (Prescribed Limit) (Scotland) Regulations 2014). England & Wales limit referenced from Road Traffic Act 1988 (Section 11(2)). Hepatic clearance and pharmacokinetic models reference Watson, Watson & Batt (1980; 1981) and Jones AW (2010).