What is the legal BAC limit in the US?

0.08% for drivers 21 and over in all states; for under 21, limits range from 0.01% to 0.05%.

How fast does BAC drop?

Roughly 0.015% per hour on average — about one standard drink per hour.

Why do women reach higher BAC?

Lower body water and a smaller distribution ratio (r ≈ 0.55 vs 0.68) mean the same drinks produce a higher concentration.

BAC Calculator

Estimates blood alcohol concentration from drinks consumed, body weight, gender and elapsed time using the Widmark formula, and shows time until you would be below the US 0.08% driving limit.

#bac calculator#blood alcohol#widmark#drunk driving limit#alcohol metabolism

Live calculate

Presets

Unit System

Metric (kg)Imperial (lb)

Enter your values in the matching fields — the other unit set is ignored.

Gender

MaleFemale

Body Weight

Time Since First Drink

hours

Additional Minutes

min

Beers

12 oz / 330 ml bottle at 5% ABV = 1 US standard drink.

Glasses of Wine

5 oz / 150 ml glass at 12% ABV = 1 standard drink.

Shots of Liquor

1.5 oz / 50 ml shot at 40% ABV = 1 standard drink.

Other Drinks

Custom drinks — set size and ABV below.

Other Drink Size

Other Drink ABV

Live mode: results update as you type.

Estimated BAC

0.029%

Some impairment possible — do not drive

Alcohol consumed: 28.0 g ≈ 2.0 US standard drinks (14 g each)
Widmark distribution: r = 0.68 (male) · 70.0 kg
Time elapsed: 2.0 hr · metabolism 0.015%/hr
Time until below 0.08%: Already below
Time until 0.00%: 1.9 hr

Impairment by BAC

0.0%

Euphoria / impaired

Minimal< 0.02Euphoria / impaired0.02–0.05US legal limit0.05–0.08Over-expression0.08–0.15Severe impairment0.15–0.3

Effects by blood alcohol concentration

BAC (%)	Behavior	Impairment
0.001–0.029	Appears normal	Subtle effects detectable with special tests
0.030–0.059	Mild euphoria, relaxation, talkativeness	Concentration
0.060–0.099	Blunted feelings, disinhibition	Reasoning, depth perception, peripheral vision
0.100–0.199	Over-expression, nausea possible	Reflexes, reaction time, staggering, slurred speech
0.200–0.299	Nausea, vomiting, emotional swings	Severe motor impairment, memory blackout
0.300–0.399	Stupor, lapses in consciousness	Breathing, heart rate
0.400+	Coma possible	High possibility of death

NEVER drink and drive. Individual BAC varies with food, medications and tolerance — err on the side of caution. Estimates for informational purposes only — not medical advice.

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Formula

Widmark: BAC% = A / (W × r) × 100 − 0.015 × hours, where A = grams of alcohol (1 US standard drink ≈ 14 g), W = body weight in grams, r = 0.68 (male) / 0.55 (female)

• Convert drinks to grams of alcohol (12 oz beer @5%, 5 oz wine @12%, 1.5 oz spirits @40% = 14 g each).
• Divide by body weight in grams times the gender distribution ratio r.
• Subtract 0.015% per hour of elapsed time and clamp at zero.

Pro tips

• Food in the stomach slows absorption but does not lower the final BAC peak much.
• Under-21 drivers face far stricter limits (0.01-0.05% depending on state).

FAQ

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BAC (%)

Behavior

Impairment

0.001–0.029

Appears normal

Subtle effects detectable with special tests

0.030–0.059

Mild euphoria, relaxation, talkativeness

Concentration

0.060–0.099

Blunted feelings, disinhibition

Reasoning, depth perception, peripheral vision

0.100–0.199

Over-expression, nausea possible

Reflexes, reaction time, staggering, slurred speech

0.200–0.299

Nausea, vomiting, emotional swings

Severe motor impairment, memory blackout

0.300–0.399

Stupor, lapses in consciousness

Breathing, heart rate

0.400+

Coma possible

High possibility of death

Formula

Widmark: BAC% = A / (W × r) × 100 − 0.015 × hours, where A = grams of alcohol (1 US standard drink ≈ 14 g), W = body weight in grams, r = 0.68 (male) / 0.55 (female)

• Convert drinks to grams of alcohol (12 oz beer @5%, 5 oz wine @12%, 1.5 oz spirits @40% = 14 g each).

• Divide by body weight in grams times the gender distribution ratio r.

• Subtract 0.015% per hour of elapsed time and clamp at zero.