BAC Calculator

Widmark formula · Estimated only · Not medical advice

Body Weight

Biological Sex

Time Since First Drink

min

Drinks

ABV %

Serving

12 oz

Quantity

How is this calculated?

BAC = (A x 5.14) / (W x r) - 0.015 x H

Widmark Formula

ATotal pure alcohol consumed, in fluid ounces. Calculated from each drink’s volume, ABV, and quantity.

WYour body weight in pounds. Converted automatically if you entered kilograms.

rBody water constant based on biological sex. Male = 0.73, Female = 0.66.

HHours since your first drink. The body metabolizes alcohol at approximately 0.015% BAC per hour.

The Widmark formula provides an estimate. Actual BAC varies based on metabolism, food intake, hydration, medications, and individual physiology. Results below 0.000% are displayed as 0.000% (your body has fully metabolized the alcohol).

BAC Reference

Standard drinks, ABV by category, legal limits, Widmark constants

One U.S. standard drink is 0.6 fluid ounces of pure ethanol, and almost every number that matters for sobriety scales off that anchor. Here you'll find the standard-drink definition, ABV ranges by drink category, U.S. and international legal driving thresholds, the NHTSA behavioral-effects scale, the published Widmark constants, and quick lookup tables for drinks-to-BAC by body weight.

The U.S. Standard Drink

The Dietary Guidelines for Americans and NIAAA define one standard drink as 0.6 fluid ounces (14 grams) of pure ethanol. The familiar serving sizes derive from that anchor and the typical ABV of each category.

Drink	ABV	Serving size	Pure alcohol
Regular beer	5%	12 fl oz	0.6 fl oz
Light beer	4.2%	12 fl oz	0.50 fl oz
Malt liquor	7%	8.5 fl oz	0.6 fl oz
Table wine	12%	5 fl oz	0.6 fl oz
Fortified wine (port, sherry)	17%	3.5 fl oz	0.6 fl oz
80-proof distilled spirits	40%	1.5 fl oz	0.6 fl oz
100-proof distilled spirits	50%	1.2 fl oz	0.6 fl oz

To convert any drink to standard drinks:

standard_drinks = (volume_oz × ABV%) / 60

A 16 oz pour of a 7.2% craft IPA works out to (16 × 7.2) / 60 = 1.92 standard drinks. A 4 oz martini made from 80-proof gin is (4 × 40) / 60 = 2.67 standard drinks.

ABV Ranges by Drink Category

Beer

Beer style	Typical ABV	Range
Light lager (Bud Light, Miller Lite)	4.2%	3.5–4.5%
Standard lager (Budweiser, Heineken)	5.0%	4.5–5.5%
Pale ale	5.5%	4.8–6.5%
IPA (West Coast, session)	6.5%	5.5–7.5%
Hazy / New England IPA	6.8%	6.0–8.0%
Double / imperial IPA	8.5%	7.5–10.5%
Standard stout	5.5%	4.0–7.0%
Imperial / barrel-aged stout	10.0%	8.0–14.0%
Hard seltzer	5.0%	4.5–6.0%
Hard cider	5.5%	4.0–8.5%

Wine

Wine type	Typical ABV	Range
Sparkling (champagne, prosecco, cava)	12%	10.5–13%
White (chardonnay, sauvignon blanc, riesling)	12%	9.5–14%
Light red (pinot noir, beaujolais)	12.5%	11–13.5%
Heavy red (cabernet, syrah, zinfandel)	14.5%	13.5–16%
Fortified (port, sherry, madeira)	18%	15–22%
Sake	16%	14–20%

Spirits

Spirit	Proof	ABV
Vodka, gin, rum, tequila, whiskey (standard)	80	40%
Bourbon (bottled-in-bond)	100	50%
Cask-strength whiskey	110–140	55–70%
Liqueurs (Baileys, Kahlua, amaretto)	30–70	15–35%
Aperitifs (Aperol, Campari)	22 / 50	11% / 25%
Everclear (grain alcohol)	190	95%

Cocktails

Cocktail	ABV (in glass)	Standard drinks
Martini (2.5 oz gin, 0.5 oz vermouth)	32%	~1.6
Manhattan (2 oz whiskey, 1 oz vermouth)	27%	~1.3
Margarita (2 oz tequila, 1 oz triple sec)	18%	~1.6
Old Fashioned (2 oz whiskey, sugar, bitters)	35%	~1.3
Negroni (1 oz each gin, Campari, vermouth)	24%	~1.3
Long Island Iced Tea (2 oz mixed spirits + cola)	22%	~1.7
Mimosa (2 oz champagne, 2 oz juice)	6%	~0.4

Bartender pours run heavy. A “1.5 oz” free-pour without a jigger commonly lands between 1.7 and 2.2 oz, which adds 15–45% to the standard-drink count.

U.S. Legal Driving Limits

The per se BAC is the threshold at which driving is illegal regardless of impairment evidence.

Tier	BAC threshold	Who it covers
Standard	0.08	All 50 states + DC except Utah
Standard (Utah only)	0.05	Effective December 2018
Commercial driver	0.04	All 50 states + DC
Aggravated / enhanced	0.15	Most states; triggers mandatory minimums
Under 21 zero tolerance	0.00 – 0.02	All 50 states; threshold varies

Zero-tolerance laws cover drivers under 21 in every state. Eighteen states (AK, AZ, DC, IL, IA, KS, ME, MN, NC, OK, OR, TX, WI, plus most early-adopter states) set the under-21 limit at 0.00 or 0.01. The remaining states use 0.02. California and New Jersey are at 0.01. All other limits scale from those tiers.

International Driving Limits (Selected)

Country	BAC	Notes
Brazil, Czechia, Hungary, Romania, Saudi Arabia, UAE	0.00	Zero tolerance
Sweden, Norway, Poland	0.02
China, India, Japan	0.03
Germany	0.05	0.03 with crash or impairment evidence
France, Italy, Spain, Netherlands, Belgium	0.05
Australia, New Zealand	0.05	0.00 for novice drivers
Ireland, Portugal, Austria, Switzerland	0.05
Canada	0.08 criminal	Provinces impose 0.05 administrative
United Kingdom	0.08 / 0.05	England/Wales/NI 0.08; Scotland 0.05
Mexico	0.08 federal	States vary 0.04–0.08

Most jurisdictions enforce a lower limit for professional drivers, novice drivers, and motorcyclists.

BAC Behavioral Effects (NHTSA Scale)

What blood alcohol concentration typically looks like in observable behavior. Individual response varies with tolerance, food, medication, and rate of consumption.

BAC	Typical effects
0.020	Mild relaxation, slight body warmth, reduced visual tracking
0.050	Lowered alertness, reduced coordination, impaired multitasking
0.080	Poor muscle coordination, slurred speech, reduced reaction time — U.S. per se limit
0.100	Clear deterioration of reaction time, pronounced steering drift
0.150	Major loss of balance, vomiting possible, substantial driving impairment
0.200	Disorientation, confusion, possible blackout
0.300	Stupor, possible loss of consciousness
0.400	Onset of coma, possible death from respiratory arrest
0.450+	Death from respiratory arrest likely

Source: NHTSA, “The ABCs of BAC” (DOT HS 809 844).

Widmark Formula and Constants

The equation Sober uses:

BAC% = (A × 5.14) / (W × r) − 0.015 × H

A = ounces of pure ethanol consumed
W = body weight in pounds
r = body water distribution constant
H = hours elapsed since first drink
5.14 = unit conversion (oz to g per dL)
0.015 = average hourly elimination rate

The metric form, more common in scientific literature: BAC (g/L) = A_grams / (W_kg × r) − β × t, where β ≈ 0.15 g/L per hour.

Published r values from major sources:

Source	Male r	Female r	Method
Widmark (1932)	0.68	0.55	Original Swedish sample
Watson, Watson & Batt (1981)	0.71	0.58	Total body water regression
Forrest (1986)	0.71	0.58	Cadaver dissection refinement
Seidl, Jensen & Alt (2000)	0.74	0.58	Height-weight regression
Sober default	0.73	0.66	Online-calculator convention

Switching from 0.73/0.66 to Widmark’s original 0.68/0.55 raises a calculated BAC by roughly 7% for men and 20% for women on the same inputs.

The elimination constant β:

Population	Rate (%/hr)
Healthy social drinker (average)	0.015
Light / occasional drinker	0.013–0.017
Heavy / habitual drinker	0.017–0.022
Chronic alcoholic in withdrawal	0.025–0.040
Very low BAC (under 0.02%)	0.008–0.012

Drinks-to-BAC Lookup (Peak, No Metabolism)

How a single standard drink lands at peak absorption, by sex and body weight. Subtract approximately 0.015% for every hour elapsed since the first drink.

Men (r = 0.73)

Body weight	1	2	3	4	5
120 lb	0.035	0.070	0.105	0.140	0.175
140 lb	0.030	0.060	0.090	0.120	0.150
160 lb	0.026	0.053	0.079	0.106	0.132
180 lb	0.023	0.047	0.070	0.094	0.117
200 lb	0.021	0.042	0.063	0.084	0.105
220 lb	0.019	0.038	0.057	0.076	0.095
240 lb	0.018	0.035	0.053	0.070	0.088

Women (r = 0.66)

Body weight	1	2	3	4	5
100 lb	0.047	0.094	0.141	0.188	0.235
120 lb	0.039	0.078	0.117	0.156	0.195
140 lb	0.033	0.067	0.100	0.134	0.167
160 lb	0.029	0.058	0.088	0.117	0.146
180 lb	0.026	0.052	0.078	0.104	0.130
200 lb	0.023	0.047	0.070	0.094	0.117

Time-to-Zero Quick Reference

Hours until BAC returns to 0.000% at the standard 0.015%/hr elimination rate.

Peak BAC	Hours to 0.000
0.020	1h 20m
0.040	2h 40m
0.060	4h 00m
0.080	5h 20m
0.100	6h 40m
0.120	8h 00m
0.150	10h 00m
0.180	12h 00m
0.200	13h 20m
0.250	16h 40m
0.300	20h 00m

A useful field check: peak ÷ 0.015 = hours back to sober.

Alcohol Metabolism Over Time (BAC Decline Chart)

The body clears alcohol at a near-constant rate — roughly 0.015% BAC per hour for an average social drinker, regardless of coffee, water, or a cold shower. Once absorption finishes, BAC falls in a straight line. This chart shows how much BAC remains hour by hour from a given peak. Read down a column to watch a starting BAC metabolize to zero.

Hours after peak	0.08 peak	0.12 peak	0.16 peak	0.20 peak
0 h	0.080	0.120	0.160	0.200
1 h	0.065	0.105	0.145	0.185
2 h	0.050	0.090	0.130	0.170
3 h	0.035	0.075	0.115	0.155
4 h	0.020	0.060	0.100	0.140
5 h	0.005	0.045	0.085	0.125
6 h	0.000	0.030	0.070	0.110
8 h	0.000	0.000	0.040	0.080
10 h	0.000	0.000	0.010	0.050
12 h	0.000	0.000	0.000	0.020

Time to sober (worked example). Three 5% beers in three hours for a 180 lb man peaks near 0.070% while drinking, but metabolism is already running — subtract 0.015% × 3 h = 0.045%, so the actual BAC after the third beer is about 0.025%. From there: 0.025 ÷ 0.015 ≈ 1 h 40 m to reach 0.000%. The same three beers downed in one hour peak near 0.055% and take roughly 3 h 40 m to clear. Pace matters: spreading drinks out lets elimination cancel part of each peak.

Linear decline assumes the standard 0.015%/hr rate after absorption completes. Individual rates vary 0.013–0.022%/hr (see Widmark constants above).

BAC by Number of Drinks (Peak, Standard Beers)

Approximate peak BAC after 1, 2, 3, or 4 standard 5% beers (12 fl oz each), before any metabolism, by sex and body-weight band. To answer “BAC after 3 beers” for a 180 lb man, read the 180 lb row and the 3-beer column, then subtract 0.015% for each hour since the first sip.

Men (r = 0.73)

Body weight	1 beer	2 beers	3 beers	4 beers
140 lb	0.030	0.060	0.090	0.120
160 lb	0.026	0.053	0.079	0.106
180 lb	0.023	0.047	0.070	0.094
200 lb	0.021	0.042	0.063	0.084
220 lb	0.019	0.038	0.057	0.076

Women (r = 0.66)

Body weight	1 beer	2 beers	3 beers	4 beers
120 lb	0.039	0.078	0.117	0.156
140 lb	0.033	0.067	0.100	0.134
160 lb	0.029	0.058	0.088	0.117
180 lb	0.026	0.052	0.078	0.104
200 lb	0.023	0.047	0.070	0.094

One beer rarely clears the 0.08% limit on its own; three beers in quick succession puts most adults at or over it. Higher-ABV craft beer (7–9%) counts as 1.5–1.8 standard drinks each, so scale these numbers up accordingly. Enter your own ABV and timing in the calculator above for a live figure, or see /learn for how the formula works.

Estimates only. These are peak-absorption figures, not a measurement — never use a calculator to decide whether to drive. When in doubt, don't drink and drive.

Standard Drinks to Reach the 0.08 Limit

Working backward from the U.S. per se limit: roughly how many standard drinks (0.6 fl oz of ethanol each) it takes for peak BAC to reach 0.08%, by sex and body weight, before any metabolism. The body starts to metabolize alcohol right away, near 0.015% per hour, so over a longer session the real count needed to measure 0.08 sits above these peak figures. Treat them as a ceiling estimate, not a green light.

Men (r = 0.73)

Body weight	Drinks to 0.08
140 lb	2.7
160 lb	3.0
180 lb	3.4
200 lb	3.8
220 lb	4.2

Women (r = 0.66)

Body weight	Drinks to 0.08
120 lb	2.1
140 lb	2.4
160 lb	2.7
180 lb	3.1
200 lb	3.4

Estimate only, not medical or legal advice. Landing under a number here does not mean you are below the limit, sober, or safe or legal to drive: alcohol may still be absorbing, bodies vary widely, and measurable impairment starts well below 0.08%. Never use this table, the metabolism chart above, or the sober calculator to decide whether to drive. When in doubt, don't drink and drive.

Blood alcohol vs breath alcohol. Forensic breath testers report BrAC; the legal “BAC” in most states is BrAC converted with a 2,100:1 partition ratio.
TAC (transdermal alcohol concentration). Wearables like SCRAM and BACtrack Skyn measure ethanol diffusing through skin. TAC tracks BAC with a 60–120 minute lag.
Per se vs zero-tolerance vs aggravated. Three independent BAC thresholds appear in U.S. law for the same driver.
Implied consent. Refusing a BAC test triggers automatic license suspension in all 50 states, separate from any DUI charge.
ADH and ALDH. Two enzymes that metabolize ethanol; genetic variants account for much of the population-level difference in tolerance.

BAC Calculator

BAC Reference

The U.S. Standard Drink

ABV Ranges by Drink Category

Beer

Wine

Spirits

Cocktails

U.S. Legal Driving Limits

International Driving Limits (Selected)

BAC Behavioral Effects (NHTSA Scale)

Widmark Formula and Constants

Drinks-to-BAC Lookup (Peak, No Metabolism)

Men (r = 0.73)

Women (r = 0.66)

Time-to-Zero Quick Reference

Alcohol Metabolism Over Time (BAC Decline Chart)

BAC by Number of Drinks (Peak, Standard Beers)

Men (r = 0.73)

Women (r = 0.66)

Standard Drinks to Reach the 0.08 Limit

Men (r = 0.73)

Women (r = 0.66)

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