How is BAC calculated?

The Widmark formula: BAC = (A × 5.14) ÷ (W × r) − 0.015H, where A is fluid ounces of pure alcohol, W is weight in pounds, r is 0.73 for men or 0.66 for women, and H is hours elapsed. Three standard drinks over two hours for a 160 lb man estimates roughly 0.049.

How long does it take to sober up?

BAC falls by roughly 0.015 per hour and nothing speeds that up. From 0.08 that is over five hours to zero. Because drinking usually ends late at night, people are still over the limit the following morning more often than they realise — 0.12 at 2am is about 0.03 at 8am.

What is one standard drink?

0.6 fl oz (14 g) of pure alcohol — 12 oz of 5% beer, 5 oz of 12% wine, or 1.5 oz of spirits. A generous wine pour is easily two standard drinks and a 16 oz craft beer at 8% is over two, which is why counting glasses understates intake.

Can I use this to decide if I can drive?

No. Individual variation in metabolism, stomach contents, body composition and medication produces differences much larger than the margin between 0.07 and 0.08. Impairment also begins around 0.02, far below the legal limit. If you have been drinking, do not drive.

Does coffee or food sober you up?

No. The liver clears alcohol at a roughly fixed rate and nothing accelerates it. Coffee makes you feel more alert while leaving BAC and impairment unchanged, which can be more dangerous than simply feeling drunk. Food eaten before drinking slows absorption; eaten after, it does nothing.

Why do women reach a higher BAC on the same drinks?

Mainly body water distribution. Alcohol disperses into body water rather than fat, and the Widmark ratio reflects this at 0.66 for women versus 0.73 for men. Differences in the stomach enzyme that begins metabolising alcohol also contribute. On identical consumption, a 120 lb woman can exceed 0.08 where a 160 lb man reaches roughly 0.05.

Blood Alcohol Content (BAC) Calculator

Estimate blood alcohol level using the Widmark formula. For educational purposes only — never use to determine fitness to drive.

Body Weight (lbs)

Gender

Standard Drinks Consumed

1 drink = 12oz beer, 5oz wine, or 1.5oz spirits

Hours Since First Drink

BAC Estimate

0.049%

Estimated Blood Alcohol Content

Mild

Level

3.3h

Hours to Sober

0.080%

Legal Limit (US)

✓ Under Legal Limit

Status

Estimated BAC: 0.049% — Mild. Your body metabolizes ~0.015% per hour. You'll be sober in ~3.3 hours.

Analysis & insights

Your estimated BAC is 0.049%, which would take approximately 3.3 hours to return to zero at the average elimination rate of 0.015%/hour. This is below the legal limit but above the NHTSA "buzzed driving" threshold. Studies show measurable impairment even at this level. Critical: this calculator is a rough estimate. Your actual BAC varies by ±30% based on individual factors. Never use a calculator to decide whether to drive.

Mild impairment

Subtle effects: minor relaxation, reduced inhibition. NOT safe for skilled tasks.

Risk & benchmark gauge

Current band

Mild

BAC: 0.049%

0255075100

SoberMildModerateAbove legalSevere

Industry benchmarks

Your estimated BAC0.049%
No effects threshold0.020%
Buzzed driving (NHTSA)0.040%
US legal limit (drive)0.080%
Severe impairment0.150%+
Hours until sober3.3 hrs

Key insights

This is an ESTIMATE, not a measurement

The Widmark formula gives a population-average BAC. Your actual BAC varies by ±30% based on stomach contents, body composition, medications, and individual liver function. Never rely on a calculator to decide whether to drive.

You eliminate alcohol at a constant rate

The average adult metabolizes about 0.015% per hour. Coffee, cold showers, and food do NOT speed this up — only time.

Impairment starts well below 0.08%

Studies show measurable impairment in reaction time, lane control, and judgment as low as 0.02%. The legal limit is the LEGAL line, not the SAFE line.

Recommended actions(4)

If you've been drinking AT ALL, do not drive

High priority

Use Uber, Lyft, public transit, designated driver, or stay where you are. The cost of a ride is dramatically less than a DUI ($10K+) or a fatality.

Impact: A first-offense DUI typically costs $10,000-15,000 in fines, legal fees, insurance hikes, and lost wages.

Wait 4 hours before driving

High priority

At your estimated BAC of 0.049%, you need roughly 3.3 hours to drop to 0.0%. Add a buffer.

Impact: Even after BAC drops to zero, hangover impairment persists for additional hours.

Drink water alongside alcohol

Medium priority

Slows absorption, reduces hangover severity, and gives you a natural pacing mechanism. Aim for 1 glass of water per alcoholic drink.

Related Calculators

BMI Calculator

Check your Body Mass Index

Try it

Calorie Calculator

Find your daily calorie needs

Try it

TDEE Calculator

Calculate calories you burn daily

Try it

Macronutrient Calculator

Daily protein, carbs & fat targets

Try it

This tool is for informational purposes only and does not constitute medical advice. Consult a healthcare professional for advice specific to your situation.

What is Blood Alcohol Content (BAC)?

Blood alcohol content is the percentage of alcohol in your bloodstream — a BAC of 0.08 means 0.08 grams of alcohol per 100 millilitres of blood. It is the measure every drink-driving law in the United States is written around.

This calculator uses the Widmark formula, which dates to the 1930s and estimates BAC from body weight, sex, drinks consumed and time elapsed. It is the standard approach, and it is genuinely useful for understanding how alcohol accumulates and clears.

It is not accurate enough to decide whether you are safe to drive, and no online calculator is. Individual variation in metabolism, stomach contents, medication, hydration and body composition produces differences far larger than the legal margin between 0.07 and 0.08. Treat the output as education about how alcohol behaves, never as clearance to get in a car.

The formula — how to calculate Blood Alcohol Content (BAC)

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

A: = fluid ounces of pure alcohol consumed — one US standard drink contains 0.6 fl oz
W: = body weight in pounds
r: = the Widmark distribution ratio: roughly 0.73 for men, 0.66 for women
H: = hours since drinking began
0.015: = the average rate BAC falls per hour as the liver metabolises alcohol

The units matter enormously. The 5.14 constant expects alcohol in fluid ounces; using grams instead inflates the result by more than twentyfold. A calculator returning a BAC above about 0.4 from a handful of drinks has a unit error, not a dangerous drinker.

Step-by-step example

01A 160 lb man drinks 3 standard drinks over 2 hours.
02Pure alcohol: 3 × 0.6 = 1.8 fl oz.
03Numerator: 1.8 × 5.14 = 9.25.
04Denominator: 160 × 0.73 = 116.8.
05Before metabolism: 9.25 ÷ 116.8 = 0.0792.
06Subtract elimination over 2 hours: 0.015 × 2 = 0.03.
07Estimated BAC: 0.0792 − 0.03 ≈ 0.049.
08The same three drinks in a 120 lb woman: (1.8 × 5.14) ÷ (120 × 0.66) − 0.03 = 0.1168 − 0.03 ≈ 0.087 — above the 0.08 limit on identical consumption.

What counts as one standard drink

Nearly every miscalculation starts here. A "drink" is a specific quantity of pure alcohol, not a glass of whatever size the bar uses.

One US standard drink = 0.6 fl oz (14 g) of pure alcohol

Beverage	Typical strength	One standard drink
Regular beer	5% ABV	12 fl oz
Malt liquor	7% ABV	8–9 fl oz
Table wine	12% ABV	5 fl oz
Fortified wine	17% ABV	3–4 fl oz
Spirits	40% ABV	1.5 fl oz

A generously poured glass of wine can easily be two standard drinks, and a craft beer at 8% ABV in a 16 oz glass is over two. Counting glasses rather than standard drinks is the most common way people underestimate their intake.

Why the estimate cannot be trusted for driving

The Widmark formula assumes an average person with average physiology, and the deviations are large in both directions.

Food in the stomach slows absorption substantially, so the same drinks on an empty stomach produce a materially higher peak. Body composition matters because alcohol distributes into water rather than fat, so two people of identical weight but different body composition reach different levels. Sex differences go beyond the r value — differences in the enzyme that begins breaking down alcohol in the stomach also contribute.

Elimination varies too. The 0.015 per hour figure is an average; real rates range roughly from 0.010 to 0.020, which over five hours is a spread of 0.05 in BAC — larger than the entire gap between sober and the legal limit.

Medications interact unpredictably, and several common ones amplify impairment without changing BAC at all. Which raises the more fundamental point: impairment and BAC are not the same thing. Reaction time and judgement degrade measurably from around 0.02, well below any legal threshold.

There is no safe BAC for driving

Measurable impairment of reaction time and judgement begins around 0.02, far below the 0.08 legal limit in most states — and Utah sets its limit at 0.05. Commercial drivers face 0.04, and under-21 drivers are subject to zero-tolerance laws in every state. If you have been drinking at all, the defensible decision is not to drive.

How alcohol actually clears

The liver metabolises alcohol at a roughly constant rate regardless of how much you have consumed. This is why BAC falls in a straight line rather than tapering, and why the only thing that lowers it is time.

Coffee, cold showers, exercise, water and food do not accelerate elimination. They can make someone feel more alert while leaving BAC unchanged, which is arguably worse than feeling drunk — it produces a confident impaired driver rather than a cautious one.

At the average 0.015 per hour, someone at 0.08 needs over five hours to reach zero. Because drinking usually ends late, this is why people are still over the limit the next morning far more often than they expect. A BAC of 0.12 at 2am is roughly 0.03 at 8am — still impaired, and in some states still illegal.

Impairment by BAC (NHTSA)

BAC	Typical effects
0.02	Some loss of judgement; altered mood; reduced ability to track a moving target
0.05	Reduced coordination and alertness; impaired steering response
0.08	Poor muscle coordination, impaired reasoning; legal limit in most states
0.10	Clear deterioration of reaction time and control
0.15	Substantial loss of balance and vehicle control

Effects at a given BAC vary with tolerance, but tolerance affects how impairment feels rather than how much it degrades performance.

Key considerations

Count standard drinks, not glasses — pour size and ABV vary enormously.
Food slows absorption; drinking on an empty stomach raises the peak substantially.
Only time lowers BAC. Coffee and food change how you feel, not your level.
Elimination rates vary from about 0.010 to 0.020 per hour between individuals.
Impairment begins around 0.02, well below any legal limit.
Utah sets 0.05; commercial drivers 0.04; under-21 zero tolerance in all states.
Medications can amplify impairment without raising BAC at all.

Common mistakes to avoid

Using an estimate to decide whether to drive — no calculator is accurate enough for that.
Counting glasses rather than standard drinks, which understates intake badly.
Believing coffee, a shower or a meal speeds up sobering.
Assuming a night's sleep clears alcohol; at 0.015 per hour it often does not.
Treating tolerance as safety — it changes perception, not performance.
Applying the 0.08 threshold when your state, licence class or age imposes a lower one.

Frequently asked questions

Sources & references

Written and fact-checked by the CalcProLabs Editorial Team against Widmark formula and NHTSA impairment data. Read our calculation methodology and editorial policy.

Last updated July 28, 2026