- Global Driving Limits: 0.08% BAC in US, Canada, and UK; 0.5 g/L (0.5‰) across continental Europe; strict 0.2‰ (near-zero) in Sweden, Norway, and Poland.
- Novice and Commercial Rules: Professional operators and probationary drivers face strict 0.00% to 0.02% limits in virtually all jurisdictions.
- Per Se Enforcement: Exceeding the statutory threshold is an automatic offense regardless of whether observable impairment is demonstrated.
- Safe Decision: Because metabolic rates vary unpredictably, zero alcohol is the only dependable legal protection when driving.
Why this page does not calculate a drink allowance
People searching for an alcohol legal limit calculator often want to turn a local threshold into a maximum number of drinks. That reverses an uncertain model into advice it cannot support. Serving sizes, body composition, absorption and metabolism vary too much for a dependable allowance.
This page instead explains the limits of that approach and links to official rules. If you want to understand the mathematics, the BAC calculator demonstrates a simplified estimate. Its result must not be used to decide whether to drive, and it does not establish a legal defense.
United States: state and driver-category differences
The CDC describes a 0.08% BAC legal threshold for adult drivers in most US states, with Utah using 0.05%. These familiar figures are not the whole law. Commercial, underage and other driver categories can be subject to stricter requirements, and impaired driving can have consequences below a per-se threshold.
Check the current official rules for the state and driver category involved. Do not assume a threshold quoted for a private adult driver applies to a commercial vehicle or a younger driver. The CDC impaired-driving overview and NHTSA's driving guidance provide context; the relevant state authority is the source for a specific legal situation.
United Kingdom: Scotland has different limits
| Jurisdiction | Blood | Breath |
|---|---|---|
| England, Wales and Northern Ireland | 80 mg / 100 ml | 35 micrograms / 100 ml |
| Scotland | 50 mg / 100 ml | 22 micrograms / 100 ml |
These figures are from GOV.UK's drink-drive limit reference, checked for this edition on 9 October 2026. The blood figures correspond to 0.08% and 0.05% respectively. The breath figures use a different sample and unit; do not substitute one bare number for another.
The government explicitly cautions that it is not possible to translate the legal limit into a set number of drinks. Always check the current official source before relying on legal information, particularly when travelling between jurisdictions.
Australia, Canada and international travel
Australia and Canada have state, territory or provincial rules as well as driver-category distinctions. Novice, learner and professional drivers may face different requirements from other adults. Local sanctions and procedures cannot be captured by selecting one universal country threshold.
For Australia, begin with the road authority in the relevant state or territory. For Canada, use the provincial or territorial transport authority alongside federal impaired-driving information. Elsewhere, consult the destination's official transport or police guidance. A translated calculator does not replace the law, and a standard-drink definition does not determine a driving limit.
Commercial, novice and zero-tolerance rules in the US
The 0.08% figure people quote is the per-se threshold for private adult drivers in almost every US state, but federal and state layers add more rules. Under Federal Motor Carrier Safety Administration regulations, a commercial driver operating a commercial vehicle is over the limit at 0.04%. Every state also enforces zero-tolerance laws for drivers under the legal drinking age, commonly set at 0.01% or 0.02%, and graduated-licence conditions can add their own restrictions.
Utah's general limit is 0.05%, a deliberate policy difference from the rest of the country. Many states further define aggravated categories — commonly starting at 0.15%, sometimes 0.20% — with tougher penalties, mandatory assessment or ignition-interlock requirements that can apply even on a first offence. A calculator that outputs one number cannot track any of these categories, which is why checking the state authority for the driver category involved is non-negotiable.
Australia and Canada in more detail
In Australia, general limits are 0.05% across most jurisdictions, with 0.00% applying to novice, learner and some professional drivers depending on the state or territory. Random breath testing is widespread, and police do not need suspicion of impairment to stop a driver and require a breath sample in most jurisdictions. Penalties and licence actions are set by each state or territory.
Canada's Criminal Code framework addresses impaired driving federally, with provinces and territories adding administrative licence suspensions that can begin well below the criminal thresholds — in some provinces, in the 0.05% warning range. That means a driver can lose their licence temporarily at a concentration that would not lead to a criminal charge. Provincial rules, not a country-wide number, determine those consequences.
How limits are actually enforced
A per-se limit lets enforcement act on a measured concentration alone, without proving visible impairment. But it is not the only tool. An officer can still base an arrest on observed driving, field sobriety tests or the smell of alcohol, and in many places a drug-recognition evaluation can follow. Refusing a lawful demand for a breath or blood sample is itself an offence in most jurisdictions, often carrying penalties comparable to being over the limit.
This matters for calculator thinking: passing “under 0.08%” does not end the encounter, because impairment-based charges, refusing to provide a sample, and zero-tolerance or commercial categories each operate independently of the per-se number. The only approach that interacts safely with all of these rules is not driving after drinking.
Read the unit before reading the number
A blood concentration written as 0.05% is equivalent to 0.5 g/L or 50 mg per 100 ml. In common BAC usage, that is also expressed as 0.5 per mille. A breath concentration is a different measurement and should be interpreted using the official breath unit and rule.
A tenfold error can occur if a percentage is confused with per mille. The BAC chart illustrates blood-unit conversions. When comparing a device reading with an official threshold, first verify the sample type and unit; if unsure, ask a qualified professional rather than making a casual conversion.
Below a threshold does not mean unimpaired
Alcohol can affect attention, judgment and coordination before a commonly quoted legal threshold is reached. Fatigue, medication and other substances can add to the problem. The existence of a threshold should not be interpreted as a guarantee of safe performance below it.
Likewise, a mathematical estimate below a threshold does not prove that a real measurement would be below it. The model may understate alcohol because a serving was larger, a drink was stronger or absorption was ongoing. This is why our calculator does not show green “safe” badges or a legal countdown.
A practical checklist for information, not clearance
Identify the jurisdiction and driver category. Open the official source and check its date and measurement units. Distinguish a blood threshold from a breath threshold and a general explanation from the full applicable law. Seek qualified legal advice for a specific incident or dispute.
For an upcoming journey after drinking, arrange alternative transport instead of trying to calculate a permitted dose. The driving-after-drinking guide explains why waiting-time rules fail. No page on this site certifies fitness to drive or replaces medical or legal advice.