Blood alcohol content (BAC) calculator

Blood alcohol content (BAC) estimate by the Widmark formula from drinks, body weight and time, with the elimination curve and time back to zero.

업데이트 검증한 예제: 5

One US standard drink = 14 g alcohol: 12 fl oz beer at 5%, 5 fl oz wine at 12%, or 1.5 fl oz spirits at 40% (NIAAA).
Hours, or 1:30 for an hour and a half.
시도하기
Estimated BAC now
%
Estimated BAC now: 0.042 %
소수 자릿수: 3; 가장 가까운 값, 중간값은 0에서 먼 쪽으로
Estimate before elimination
0.072%
Time until the estimate reaches 0
2 h 47 min 26 s
Estimated BAC now
0.42‰ (g/L)
Pure alcohol
42.0g
Informational only — never use this estimate to decide whether to drive, operate machinery or look after others. Impairment starts well below legal limits, and real absorption varies with food, medication, health and drinking pace.

By the Widmark estimate, blood alcohol is about 0.042% now and falls to zero in roughly 2 h 47 min. This is an average-person model, not a measurement.

Estimated BAC after the first drink

00.020.040.060.0801234Hours since the first drinkBAC (%)Now: 0.042%0.08%: legal limit in most US states; impairment starts lower
계산 방법 S
  1. Pure alcohol

    A=3×0.6 fl oz=1.8 fl oz (42.0 g)A = 3 \times 0.6\ \text{fl oz} = 1.8\ \text{fl oz}\ (42.0\ \text{g})
  2. Widmark distribution

    1.8000×5.14176.4 lb×0.73=0.0719%\frac{1.8000 \times 5.14}{176.4\ \text{lb} \times 0.73} = 0.0719\%

    r = 0.73 for men: the share of body weight that holds the alcohol.

  3. Subtract elimination

    0.0719−0.015×2.00=0.0419%0.0719 - 0.015 \times 2.00 = 0.0419\%

    0.015 % per hour is an average elimination rate; individual rates differ.

  4. Time back to zero

    0.07190.015−2.00 h=2.79 h\frac{0.0719}{0.015} - 2.00\ \text{h} = 2.79\ \text{h}

Blood alcohol content (BAC) calculator 소개

Blood alcohol content (BAC) is estimated with the Widmark formula: the alcohol drunk is spread through a share r of body weight, 0.73 for men and 0.66 for women, and about 0.015 percentage points are eliminated per hour. In US units, BAC % = fluid ounces of alcohol × 5.14 ÷ (weight in lb × r) − 0.015 × hours. One US standard drink holds 14 g, or 0.6 fl oz, of pure alcohol (NIAAA).

People use it to see how drinks, body weight and time interact. An 80 kg man who has had 3 standard drinks over 2 hours is estimated at 0.042 %, and the estimate reaches zero about 2 h 47 min later.

The result is an average-person model, not a measurement: food, drinking pace, medicines and liver function change real BAC, and impairment begins well below legal limits. It is not a basis for deciding whether to drive.

계산 예제

Man, 180 lb, 3 standard drinks, 2 hours

Sex (for the formula)
Male
Weight
180 lb
Count alcohol as
Standard drinks
US standard drinks
3
Time since the first drink
2
Estimated BAC now
0.040 %
Estimate before elimination
0.070 %
Time until the estimate reaches 0
2 h 41 min 38 s

검증 출처: Python 3.8 decimal: 1.8 × 5.14 / (180 × 0.73) − 0.015 × 2 = 0.04041; zero after 0.070411/0.015 − 2 h = 2.6941 h

Woman, 130 lb, a 750 mL bottle of 12% wine, 3 hours

Sex (for the formula)
Female
Weight
130 lb
Count alcohol as
Volume and strength
Total volume drunk
750 mL
Alcohol by volume
12%
Time since the first drink
3
Estimated BAC now
0.137 %
Estimate before elimination
0.182 %
Time until the estimate reaches 0
9 h 9 min 14 s

검증 출처: Python 3.8 decimal: A = 750/29.5735295625 × 0.12 = 3.04326 fl oz; 3.04326 × 5.14 / (130 × 0.66) − 0.045 = 0.13731

Edge: one drink, 80 kg man, 5 hours later (floored at zero)

Sex (for the formula)
Male
Weight
80 kg
Count alcohol as
Standard drinks
US standard drinks
1
Time since the first drink
5
Estimated BAC now
0.000 %
Time until the estimate reaches 0
0 s
Estimate before elimination
0.024 %

검증 출처: Python 3.8 decimal: 0.6 × 5.14 / (176.37 lb × 0.73) = 0.02395 < 0.015 × 5, so the estimate is 0

Edge: no drinks

Sex (for the formula)
Female
Weight
60 kg
Count alcohol as
Standard drinks
US standard drinks
0
Time since the first drink
1
Estimated BAC now
0.000 %
Estimate before elimination
0.000 %
Pure alcohol
0.0 g

검증 출처: Definition: A = 0 gives BAC 0

자주 묻는 질문

What is a standard drink?

In the US, a standard drink contains 14 g (0.6 fl oz) of pure alcohol: 12 fl oz of 5 % beer, 5 fl oz of 12 % wine or 1.5 fl oz of 40 % spirits, according to NIAAA. Other countries use different sizes; a UK unit is 8 g, so one US standard drink is 1.75 UK units. A 750 mL bottle of 12 % wine holds about 71 g of alcohol, roughly 5 US standard drinks.

How is blood alcohol calculated?

With the Widmark formula. The alcohol drunk is divided by body weight times r, the share of the body that holds it (0.73 for men and 0.66 for women here), and about 0.015 percentage points are subtracted for each hour since drinking began. A 180 lb man who has 3 standard drinks (1.8 fl oz of alcohol) peaks at 1.8 × 5.14 ÷ (180 × 0.73) = 0.070 % and is estimated at 0.040 % two hours later.

How long does it take for alcohol to leave your body?

At the average elimination rate of about 0.015 percentage points per hour, a BAC of 0.08 % takes roughly 5 hours 20 minutes to reach zero. One US standard drink takes about 1.3 hours to clear for a 100 kg man and 2.8 hours for a 50 kg woman by this estimate. Coffee, water and sleep do not speed elimination; the liver sets the pace, and individual rates vary.

What BAC is the legal limit for driving?

0.08 % in every US state except Utah, which lowered its limit to 0.05 % in 2018, and 0.04 % for US commercial drivers. England, Wales and Northern Ireland use 80 mg per 100 mL of blood (0.08 %) and Scotland 50 mg (0.05 %). Impairment starts below these limits, so an estimate under the limit does not mean it is safe to drive.

“Blood alcohol content (BAC) calculator”의 정확도는 어느 정도인가요?

정확도는 입력값과 계산 방법의 가정에 따라 달라집니다. 십진 연산은 유효숫자 50자리를 사용하지만, 추정값·수치해석 방법·원본 데이터의 정밀도는 더 낮을 수 있습니다. 표시값을 반올림해도 이러한 한계는 사라지지 않습니다. 독립적인 출처의 풀이와 대조한 계산 예시: 5. 예를 들어 “Man, 180 lb, 3 standard drinks, 2 hours”은 Python 3.8 decimal: 1.8 × 5.14 / (180 × 0.73) − 0.015 × 2 = 0.04041; zero after 0.070411/0.015 − 2 h = 2.6941 h와 대조해 확인합니다.

이 계산 방법의 출처는 무엇인가요?

Widmark EMP. Die theoretischen Grundlagen und die praktische Verwendbarkeit der gerichtlich-medizinischen Alkoholbestimmung (1932); NIAAA — What is a standard drink?; NIAAA — Understanding the dangers of alcohol overdose.

이 계산기 소개

BAC%=A×5.14W×r−0.015 H(A fl oz alcohol, W lb, r=0.73 M/0.66 F, H hours)\text{BAC}\% = \frac{A \times 5.14}{W \times r} - 0.015\,H\quad(A\ \text{fl oz alcohol},\ W\ \text{lb},\ r = 0.73\ \text{M} / 0.66\ \text{F},\ H\ \text{hours})

출처

  1. Widmark EMP. Die theoretischen Grundlagen und die praktische Verwendbarkeit der gerichtlich-medizinischen Alkoholbestimmung (1932)
  2. NIAAA — What is a standard drink?
  3. NIAAA — Understanding the dangers of alcohol overdose

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