BAC Reference
Standard drinks, ABV by category, legal limits, Widmark constants
The calculator above runs the Widmark equation on your inputs. The reference below covers the data that feeds it: the U.S. 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.
- 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.