Estimate Blood Alcohol Concentration (BAC)
What this drink drive calculator is for
This drink drive calculator gives a rough estimate of blood alcohol concentration (BAC) using common alcohol-metabolism assumptions. It can help you understand risk trends, but it cannot determine whether you are safe or legal to drive at any given moment. Police breath testing, jurisdiction-specific rules, and your own level of impairment are what matter in real life.
The safest interpretation is simple: if you consumed alcohol, do not drive. Use a taxi, rideshare, public transport, or a sober driver.
How the estimate works
Inputs used by the calculator
- Body weight: Used to estimate distribution of alcohol in the body.
- Biological sex: Used for a standard Widmark distribution factor.
- Total standard drinks: Number of drinks consumed.
- Alcohol grams per drink: Lets you adapt for local definitions (10g, 12g, 14g, etc.).
- Hours since first drink: Used to subtract a typical elimination rate over time.
The model in plain language
The tool estimates peak BAC from total alcohol consumed and body distribution, then subtracts alcohol cleared over time. A common average elimination rate of 0.015 BAC% per hour is used. Real-world elimination may be faster or slower.
Why estimates can be wrong (sometimes by a lot)
Two people with the same number of drinks can show very different BAC readings. Major factors include:
- How quickly drinks were consumed
- Food in the stomach and meal timing
- Medication interactions
- Hydration, fatigue, and health conditions
- Individual metabolism differences
- Actual pour sizes (many “one drinks” are double pours)
Because of these variables, this calculator should be treated as a conservative education tool, not proof of fitness to drive.
Important legal points
Drink driving laws vary by country, region, age, and license class. Some places impose lower or zero limits for learner, provisional, commercial, or professional drivers. Penalties can include fines, disqualification, criminal records, and imprisonment.
Even below a posted legal limit, you may still be impaired and still be liable if your driving is unsafe.
Practical safer plan after drinking
- Plan your ride home before the first drink.
- Keep transport app options ready and funded.
- Use designated sober drivers (verified sober, not “less drunk”).
- Stay overnight when possible.
- If in doubt, don’t drive.
Common myths (and facts)
“Coffee will sober me up quickly.”
False. Coffee may reduce sleepiness, but it does not lower BAC. Time is the main factor.
“A cold shower fixes intoxication.”
False. A shower can make you feel more alert briefly, but alcohol levels in blood remain.
“I feel fine, so I’m okay to drive.”
False. Subjective confidence often rises while judgment and reaction time decline.
Bottom line
Use this drink drive calculator to understand risk, not to justify driving. If you drank alcohol, the safest and smartest decision is always to avoid driving entirely.