❓ Frequently Asked Questions

The calculator uses the Widmark formula, the most widely accepted mathematical model for estimating BAC. However, it is an estimate with a typical accuracy range of ±20–30%. Real BAC is affected by food consumption, individual metabolism rates, medications, and other factors that cannot be entered into a formula. Never rely on this estimate to decide whether to drive.

In the United States, one standard drink contains 14 grams of pure ethanol. This equals:

• 12 fl oz (355 mL) of regular beer (~5% ABV)
• 5 fl oz (148 mL) of table wine (~12% ABV)
• 1.5 fl oz (44 mL) of distilled spirits (~40% ABV)

Other countries define standard drinks differently (e.g., 10 g in the UK, 12.5 g in Australia). Adjust the "Alcohol per Drink" value in the calculator to match your actual drink strength.

The Widmark formula uses a body-water distribution ratio (r): 0.73 for males and 0.66 for females. Biological females generally have a higher percentage of body fat and lower percentage of body water, meaning alcohol is less diluted, resulting in a higher BAC per unit of alcohol consumed. This is purely a physiological factor used in the formula — not a social distinction.

This is the total time in hours from when you had your first drink to now. During this time your liver has been metabolising alcohol at approximately 0.015% BAC per hour. Setting a higher time will result in a lower calculated BAC because more alcohol has been eliminated. If you are calculating in advance (e.g., "what will my BAC be in 2 hours?"), use your planned future time.

Use the "Alcohol per Drink (grams)" field to adjust the default 14 g value. To calculate for a specific drink, use:

Grams = Volume (mL) × ABV (as decimal) × 0.789 (density of ethanol)

Examples:

• Strong craft beer (8%, 355 mL): 355 × 0.08 × 0.789 ≈ 22 g
• Double spirit (40%, 88 mL): 88 × 0.40 × 0.789 ≈ 28 g
• Large wine glass (13%, 250 mL): 250 × 0.13 × 0.789 ≈ 26 g

Alcohol is absorbed into the bloodstream mainly through the small intestine. BAC typically peaks 30 to 90 minutes after finishing your last drink, depending on:

• Whether you have eaten (food delays absorption significantly)
• The type and carbonation level of the drink (carbonated drinks absorb faster)
• Your individual digestive speed

The peak can come even faster (15–30 min) on an empty stomach.

The liver metabolises alcohol at a roughly constant rate of 0.010%–0.020% BAC per hour, with an average of ~0.015%. This rate is largely fixed and cannot be meaningfully increased by eating, drinking water, coffee, or exercise. For context:

• A BAC of 0.08% takes about 5–6 hours to reach 0.00%
• A BAC of 0.15% takes 8–12+ hours to reach 0.00%

This is why people who drank heavily at night may still be over the legal limit the next morning.

Yes — this is extremely common and very dangerous. Regular drinkers can develop a tolerance that reduces the feeling of intoxication at a given BAC, but their actual reaction time, coordination, and decision-making remain just as impaired. Feeling fine does not mean your BAC is below the legal limit. The only reliable way to know your BAC is with a certified breathalyser device.

No. Drinking water does not reduce your BAC or speed up alcohol metabolism. Water helps with hydration and can reduce hangover severity the next day, but it has no effect on how quickly the liver processes alcohol. The only thing that lowers BAC is time.

Once alcohol is already in your bloodstream, eating has little to no effect on BAC. Food is most effective when consumed before or while drinking — it slows absorption and lowers the peak BAC you will reach. Eating after the alcohol is already absorbed will not meaningfully speed up elimination.

Legal limits vary by country and region:

• 0.08% – USA (most states), UK (England/Wales), Canada
• 0.05% – Australia, Germany, France, most of Europe
• 0.03% – Japan
• 0.02% – Sweden, Norway, China
• 0.00% – Brazil, UAE, Saudi Arabia, and many countries for new/professional drivers

See the full table on our Safety & Legal page →

Research shows that driving ability is measurably impaired even at 0.02% BAC. At 0.05%, the risk of a fatal crash is roughly doubled compared to 0.00%. Being below the legal limit does not mean driving is safe. The safest option is always zero alcohol before driving.

Do not assume this. This calculator provides a mathematical estimate only. Your actual BAC could be significantly higher due to food intake, metabolism variation, drink strength discrepancies, and other factors. Police breathalysers are calibrated instruments — they measure your actual breath alcohol. If your estimated BAC is anywhere near the legal limit, do not drive. The consequences of a DUI conviction are severe.

Call emergency services immediately (911 / 999 / 112). While waiting:

• Place the person on their side (recovery position) to prevent choking on vomit
• Keep them warm with a blanket
• Stay with them — never leave an intoxicated person alone
• Do not give coffee, water, or food
• Do not let them "sleep it off" unattended

Warning signs: unconsciousness, slow/irregular breathing, blue-tinged skin, seizures, vomiting repeatedly.

Yes, this BAC Calculator is completely free to use. No registration, account, or payment is required. It runs entirely in your browser — no data is sent to any server.

No. All calculations happen entirely in your browser using JavaScript. No data you enter (weight, drinks, gender, etc.) is transmitted to, or stored on, any server. When you close the page, your data is gone.

No. This tool is for educational and informational purposes only. It is not a substitute for professional medical advice, a certified breathalyser, or legal counsel. Do not use it to:

• Determine whether it is safe or legal to drive
• Make clinical decisions about someone's level of intoxication
• Use in court or legal proceedings

If you need an accurate BAC measurement, use a certified breathalyser device.