BAC Calculator

How to use this BAC calculator

1. Set your sex and weight. The Widmark model distributes alcohol across body water, which differs by sex assigned at birth and scales with weight. Toggle lb/kg as needed.
2. Enter the time since your first drink — not your last one. Elimination starts working from the moment alcohol begins entering your bloodstream.
3. Tap in what you drank. The beer, wine, and liquor buttons are standard US servings (12 oz at 5%, 5 oz at 12%, 1.5 oz at 40% — each about 14 g of pure alcohol). Craft beer, cocktails, and seltzers rarely match a "standard" drink, so open the custom row and enter the real size and ABV.
4. Read the estimate and the zone. The result updates as you type — no button. The color band tells you where the number lands, from minimal impairment to medical emergency.
5. Check the sober clock. The chart below the result shows your estimated hour-by-hour decline and the approximate wall-clock times you cross 0.08, 0.05, and 0.00 — the answer to "when will my BAC be zero?"

Why this BAC calculator is different

Most BAC calculator pages do the same three things: take your inputs, print one number, and stop. Many of the rest exist to sell you something else entirely — rehab placement or DUI defense. Here's what this one adds:

• A sober clock, not just a snapshot. The single most-searched follow-up question — "when will I be back to zero?" — is exactly what a one-number calculator can't answer. This tool charts your estimated BAC hour by hour and gives you approximate clock times for crossing 0.08, 0.05, and 0.00.
• Honest about its own error bars. The Widmark formula is a population average. Real elimination rates run from roughly 0.010 to 0.025%/hour, and food, medications, and liver health move the result by ±20% or more. This page says so — repeatedly — rather than presenting three decimals as truth.
• No agenda. No rehab-center lead forms, no law-firm intake, no ads, no email gate. An educational reference reviewed by a named physician, with the math printed below.
• Custom drinks done properly. A 9% double IPA in a 16-oz pour is 2.4 standard drinks, not one. The custom row takes real sizes and ABVs instead of forcing everything into three preset buttons.
• It will never bless your driving. Some calculators effectively tell users they're "under the limit." This one is designed so no output state ever describes any BAC as safe or legal to drive — because impairment starts well below 0.08 and individual error is too large.
• Free to embed. Campus health-promotion pages, driver's-ed programs, and patient-education sites can drop this calculator into their own pages with one snippet — attribution included, no fee.

How this calculator works (the math)

Everything runs client-side in your browser — nothing you enter is sent to a server or stored.

The Widmark equation

The estimate uses the classic forensic model published by Erik Widmark in 1932 and still the basis of most BAC estimation, including NHTSA's own worksheets:

BAC (%) = (alcohol grams ÷ (body weight in grams × r)) × 100 − 0.015 × hours

where r is the Widmark distribution ratio — the fraction of body mass that alcohol effectively distributes into — set at 0.68 for males and 0.55 for females, and 0.015%/hour is the average elimination rate. Alcohol grams per drink are computed from actual volume and strength: ounces × 29.5735 × ABV × 0.789 (0.789 g/mL is the density of ethanol). A US standard drink works out to almost exactly 14 g of pure alcohol, matching the NIAAA standard-drink definition.

What the model can't capture

Widmark assumes the alcohol is fully absorbed and evenly distributed — but a large meal can cut peak BAC substantially, medications can slow clearance, and individual elimination genuinely varies about 2.5-fold. That's why this page treats the output as an educational estimate with wide error bars, never a measurement. The only ways to actually measure BAC are calibrated breath, blood, or laboratory testing.

Worked examples

"I'm 180 lb and had 4 beers over 2 hours"

Four standard beers is about 56 g of alcohol. For a 180-lb male: 56 ÷ (81,647 g × 0.68) × 100 = 0.101% at peak, minus 0.015 × 2 hours of elimination = an estimated 0.071% — in the "impaired" zone. Below 0.08 in most states, but over Utah's 0.05 limit, and with reaction time and judgment already measurably degraded. The sober clock puts this back to 0.00 in roughly 4 h 43 m.

"I'm a 140-lb woman and had 3 glasses of wine an hour ago"

Three 5-oz glasses at 12% is about 42 g of alcohol. With r = 0.55: 42 ÷ (63,503 g × 0.55) × 100 = 0.120% peak, minus one hour of elimination = 0.105% — over the legal limit everywhere in the US, and about 1 h 41 m from dropping below 0.08.

"What about 6 drinks at 120 lb?"

This is where the numbers get serious quickly: 6 standard drinks in a 120-lb female works out to an estimated 0.236% even after 3 hours of elimination — the "severe" zone, where blackouts and vomiting are likely and most states apply enhanced DUI penalties. Body size dominates BAC math; the same drinks that put a 220-lb person at 0.09 can put a 120-lb person near 0.24.

BAC effects by range

• 0.01–0.019 — subtle effects, detectable mostly on specialized tests.
• 0.02–0.049 — relaxation, mild euphoria; visual tracking and divided attention already decline (NHTSA).
• 0.05–0.079 — reduced coordination and slower reactions; illegal to drive in Utah and above the impairment threshold most safety bodies cite.
• 0.08–0.149 — legally intoxicated across the US; muscle coordination, reaction time, and self-assessment significantly impaired.
• 0.15–0.299 — roughly 2× the limit and up; vomiting, blackouts, major motor impairment; enhanced DUI penalties in most states.
• 0.30+ — potential loss of consciousness and suppressed breathing — this is alcohol-poisoning territory. If someone can't be roused, call 911.

Frequently asked questions

Can drinking water, coffee, or a cold shower lower my BAC?

No. Once alcohol is in your bloodstream, only time lowers BAC — your liver clears it at a fixed rate of roughly 0.015%/hour on average, and nothing safely speeds that up. Water helps with the dehydration that drives much of a hangover (as do electrolytes), and coffee makes you a more awake impaired person — but neither touches the number.

How long until my BAC is back to zero?

Divide your current BAC by 0.015 for the average-case answer in hours: 0.08 takes about 5 h 20 m; 0.15 takes about 10 hours. The sober-clock chart above does this automatically and converts it to actual clock times. Note that heavy nights genuinely can leave measurable BAC the next morning — 0.20 at 1 AM is still ~0.095 at 8 AM.

What would my BAC be after 10 beers?

For a 180-lb male drinking 10 standard beers over 4 hours, the model estimates about 0.19% — deep in the severe zone. For a 140-lb female, the same 10 beers estimate over 0.30%, alcohol-poisoning territory. There is no version of 10 beers that ends below the legal limit for a normal-sized adult; if you're checking, the answer is to hand someone your keys.

Is a BAC of 0.15 high?

Yes — 0.15 is nearly twice the 0.08 legal limit, the threshold where most states escalate to "aggravated" or "extreme" DUI penalties, and a level at which NHTSA data shows vastly elevated crash risk. Physically it typically means major motor impairment, possible vomiting, and a real chance of memory blackout.

How accurate is a BAC calculator?

Treat any online BAC number as ±20% or more. The Widmark model uses population-average distribution and elimination values, but stomach contents, medications (including many common prescriptions), liver function, body composition, and age all shift the real value. That's also why this tool can't tell you you're legal to drive — a calculator saying 0.07 is fully consistent with a breathalyzer saying 0.09.

Does drinking regularly change these numbers?

Tolerance changes how impaired you feel, not your BAC — the number is the same physics regardless of drinking history. What regular heavy drinking does reliably change is your blood pressure: the association is strong enough that cutting back is a first-line hypertension intervention. If you drink most days, a validated home blood pressure monitor is a worthwhile reality check.

Related tools

• Blood Pressure Log — alcohol is one of the most underrated drivers of elevated BP; track what your numbers do.
• Cholesterol Ratio Calculator — heavy drinking raises triglycerides, one of the five ratios this tool grades.
• Steps to Miles Calculator — the morning-after walk, quantified.
• Browse all free tools by Dr. Taylor →

Dr. Taylor's recommendations alongside this calculator

There is no product that lowers BAC — anything marketed that way is selling you a story. What evidence does support is treating the fluid and electrolyte losses that make the morning after miserable, settling the nausea, and being honest about what regular drinking does to your cardiovascular numbers:

• Best Electrolyte Powders — alcohol suppresses the hormone that tells your kidneys to retain water, so you lose fluid and sodium all night. A proper electrolyte mix beats plain water for rehydration; the picks are graded on sodium dose and sugar content.
• Best Motion Sickness Medicine — alcohol-related nausea and the "bed spins" run through the same vestibular pathways as motion sickness, which is why the same OTC antihistamine class helps with both.
• Best Blood Pressure Monitors — regular drinking above moderate levels measurably raises blood pressure, and it's reversible when you cut back. A validated cuff shows you your own data.

Sources & methodology

• Widmark EMP. Die theoretischen Grundlagen und die praktische Verwendbarkeit der gerichtlich-medizinischen Alkoholbestimmung (1932) — the original distribution-ratio model (r = 0.68 male / 0.55 female).
• National Institute on Alcohol Abuse and Alcoholism (NIAAA). What Is a Standard Drink? — 14 g of pure alcohol per standard US drink.
• NHTSA. The ABCs of BAC / drunk-driving impairment data — effects by BAC range and the 0.08 per-se limit.
• Cederbaum AI. Alcohol metabolism. Clin Liver Dis 2012;16(4):667–85 — elimination-rate physiology and its ~0.010–0.025%/h individual range.

This tool is reviewed annually — legal limits are re-checked against state statutes (Utah moved to 0.05 in 2018; others have considered following). About Dr. Taylor · Last reviewed July 17, 2026.

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