BAC Calculator
Estimate Blood Alcohol Content (BAC) using the Widmark formula. Calculate time to sober and understand impairment levels. For educational purposes only.
Important Safety Notice
This calculator provides estimates only for educational purposes. BAC is affected by many factors not accounted for here. Never use this calculator to determine if you are safe to drive. If you have consumed any alcohol, arrange alternative transportation.
12 oz @ 5% ABV
About the Widmark Formula
This calculator uses the Widmark formula, developed by Swedish researcher Erik Widmark in the 1930s. The formula estimates BAC based on:
- Amount of alcohol consumed (in grams)
- Body weight
- Body water constant (r factor): 0.68 for males, 0.55 for females
- Time elapsed (alcohol metabolizes at ~0.015% BAC/hour)
Formula: BAC = (Alcohol in grams / (Body weight in grams × r)) × 100 - (0.015 × hours)
About This Calculator
How long until I'm sober? The BAC Calculator estimates your Blood Alcohol Content using the scientifically-validated Widmark formula, giving you insight into how alcohol affects your body and how long it takes to metabolize.
The sobering truth: Every day, about 34 people in the United States die in drunk-driving crashes - that's one person every 42 minutes. In 2023 alone, 12,429 people died in alcohol-impaired driving deaths. Understanding BAC helps you make informed decisions that could save lives.
This educational tool shows how factors like weight, gender, drink type, and time affect your BAC and impairment level. The body metabolizes alcohol at a remarkably consistent rate of 0.015% BAC per hour - regardless of your size or how much coffee you drink. This means there's no way to "speed up" sobering up except time.
Key insight: Driving impairment begins at BAC levels as low as 0.02% - well below the 0.08% legal limit in all 50 US states. At 0.08% BAC, your crash risk is 11 times higher than a sober driver.
CRITICAL WARNING: This calculator is for educational purposes ONLY. It should NEVER be used to determine whether you are safe to drive. If you have consumed ANY alcohol, arrange alternative transportation. No estimate can account for individual variations in metabolism, medications, fatigue, or the many factors that affect impairment.
How to Use the BAC Calculator
- 1**Enter the number of standard drinks**: Count carefully - a standard drink is 12 oz beer (5%), 5 oz wine (12%), or 1.5 oz spirits (40%). Many cocktails contain 2-3 standard drinks.
- 2**Select the type of drink**: Choose beer, wine, shot, or cocktail. If drink ABV differs from standard, adjust mentally - craft beers and wines often have higher alcohol content.
- 3**Choose your biological sex**: This affects the body water constant in the Widmark formula. Males typically have 68% body water, females 55%, which significantly impacts BAC.
- 4**Enter your body weight**: Higher body weight means more dilution of alcohol. Enter in pounds or kilograms.
- 5**Input hours since your first drink**: When did you start drinking? The calculator accounts for alcohol your body has already metabolized at 0.015% per hour.
- 6**Note if you ate before drinking**: Food significantly slows alcohol absorption. Drinking on an empty stomach can nearly double your peak BAC.
- 7**Review your estimated BAC**: See your estimated blood alcohol level and the corresponding impairment level. Remember this is an estimate with ±20% variation.
- 8**Check time until sober**: See approximately how long until your BAC returns to 0.00%. Remember: there is NO way to speed this up.
Formula
BAC = (A / (W × r)) × 100 - (β × t)Where A = alcohol consumed in grams, W = body weight in grams, r = body water constant (0.68 for males, 0.55 for females), β = elimination rate (0.015% per hour), and t = time since first drink in hours.
Understanding the Widmark Formula
The Widmark formula, developed by Swedish researcher Erik Widmark in the 1930s, remains the gold standard for estimating BAC. The formula accounts for several key factors:
Body Water Constant (r-factor):
- Males: 0.68 (higher water content, lower BAC per drink)
- Females: 0.55 (lower water content, higher BAC per drink)
Standard Drink Definition: A standard drink contains approximately 14 grams of pure alcohol:
- 12 oz beer (5% ABV)
- 5 oz wine (12% ABV)
- 1.5 oz distilled spirits (40% ABV)
Alcohol Elimination Rate: The body metabolizes alcohol at a relatively constant rate of approximately 0.015% BAC per hour, regardless of body size. This is why "sleeping it off" is the only reliable way to sober up—your body simply needs time to process the alcohol.
Example Calculation: A 180 lb male who consumed 3 beers over 2 hours:
- Alcohol: 3 × 14g = 42 grams
- Weight: 180 × 453.6 = 81,648 grams
- BAC = (42 / (81,648 × 0.68)) × 100 - (0.015 × 2)
- BAC = 0.0756 - 0.030 = 0.046%
BAC Levels and Impairment
Blood Alcohol Content directly correlates with impairment levels:
| BAC Level | Impairment Effects |
|---|---|
| 0.00-0.02% | Minimal impairment, slight mood elevation |
| 0.02-0.05% | Mild relaxation, slight euphoria, reduced inhibitions |
| 0.05-0.08% | Reduced coordination, impaired judgment, slower reflexes |
| 0.08-0.10% | Significant impairment of motor control and judgment |
| 0.10-0.15% | Slurred speech, poor balance, blurred vision |
| 0.15-0.20% | Major loss of balance, potential blackouts |
| 0.20-0.30% | Severe impairment, confusion, vomiting |
| 0.30%+ | Life-threatening, risk of coma or death |
Driving Impairment Begins Early: Research shows that driving impairment begins at BAC levels as low as 0.02%, well below the legal limit. Reaction time, tracking ability, and divided attention are all affected at low BAC levels.
Legal BAC Limits by Region
United States:
- All 50 states: 0.08% for adults 21+
- Commercial drivers: 0.04%
- Under 21: Zero tolerance (0.00-0.02%)
- Enhanced penalties: Often at 0.15% or 0.16%
International Limits:
| Country | Legal Limit |
|---|---|
| Australia | 0.05% |
| Canada | 0.08% (0.05% in some provinces) |
| UK | 0.08% (0.05% in Scotland) |
| Germany | 0.05% |
| Sweden | 0.02% |
| Japan | 0.03% |
| Brazil, China, Hungary | 0.00% |
Consequences of DUI:
- License suspension
- Heavy fines ($1,000-$10,000+)
- Possible jail time
- Increased insurance rates
- Criminal record
- Ignition interlock device requirement
Factors Affecting Alcohol Absorption
The Widmark formula provides estimates, but many factors affect actual BAC:
Factors That Increase BAC:
- Drinking on an empty stomach
- Carbonated mixers (speed absorption)
- Lower body fat percentage
- Certain medications
- Fatigue or illness
- Hormonal changes
Factors That Decrease BAC:
- Eating before or while drinking
- Higher body weight
- Drinking slowly over time
- Higher water intake
Food's Impact: Eating food before drinking can reduce peak BAC by up to 50%. Food slows gastric emptying, allowing the liver more time to metabolize alcohol before it reaches the bloodstream.
Important Variables Not in the Formula:
- Individual metabolism variations
- Liver health and enzyme levels
- Tolerance (does NOT affect BAC, only perception)
- Age and overall health
- Prescription medications
Myths About Sobering Up
MYTH: Coffee sobers you up FACT: Coffee only makes you a wide-awake drunk. Caffeine cannot speed up alcohol metabolism. Your liver processes alcohol at a fixed rate of about 0.015% BAC per hour.
MYTH: Taking a cold shower helps FACT: A cold shower may make you feel more alert but does nothing to reduce BAC. You'll just be a cold, wet drunk.
MYTH: Exercise burns off alcohol FACT: While exercise may help you feel more alert, it doesn't significantly speed up alcohol metabolism. Only a tiny amount is eliminated through sweat.
MYTH: Eating after drinking reduces BAC FACT: Eating food BEFORE drinking helps. Once alcohol is in your bloodstream, eating won't remove it.
MYTH: You can "hold your liquor" better with experience FACT: Tolerance affects how impaired you feel, NOT your BAC. An experienced drinker with a 0.10% BAC is just as impaired for driving as a first-time drinker—they just feel less drunk.
MYTH: Stick to beer/wine to stay safer FACT: Standard drinks of beer, wine, and spirits contain the same amount of alcohol. The only thing that matters is total alcohol consumed.
THE ONLY REAL SOLUTION: Time is the only factor that reduces BAC. Your liver needs approximately 1 hour to metabolize one standard drink.
How Long Until I'm Sober? BAC Timeline Calculator
One of the most common questions about alcohol is "how long until I'm sober?" Here's how to calculate your sobering timeline:
The Metabolism Rate
Your body processes alcohol at a remarkably consistent rate:
- 0.015-0.016% BAC per hour (average)
- One standard drink per hour (approximately)
- This rate is constant regardless of body size, gender, or tolerance
Sobering Timeline by Peak BAC
| Peak BAC | Time to 0.00% | Example Scenario |
|---|---|---|
| 0.02% | ~1.5 hours | 1 drink, 160 lb person |
| 0.05% | ~3.5 hours | 2-3 drinks over 2 hours |
| 0.08% | ~5.5 hours | 4 drinks over 2 hours |
| 0.10% | ~6.5 hours | 5 drinks over 2 hours |
| 0.15% | ~10 hours | Heavy drinking session |
| 0.20% | ~13 hours | Binge drinking |
The Morning After Problem
Many DUI arrests happen the morning after drinking. Example:
- You drink heavily until midnight (BAC peaks at 0.15%)
- You sleep for 6 hours
- At 6 AM, your BAC is still around 0.06%
- You feel "fine" and drive to work
- You're still significantly impaired
Rule of thumb: If you drink heavily, you may not be safe to drive until well into the next afternoon.
Factors That Don't Speed Up Metabolism
| Myth | Reality |
|---|---|
| Coffee | Makes you alert but still drunk |
| Cold shower | Makes you cold but still drunk |
| Exercise | Tiny amount through sweat (~2-5%) |
| Eating after | Doesn't help - alcohol is already absorbed |
| Vomiting | Only helps if alcohol hasn't been absorbed yet |
| Fresh air | Feels nice but doesn't change BAC |
DUI Penalties and Consequences: What You Risk
Understanding the true cost of impaired driving can be a powerful deterrent. Here's what you're risking:
First Offense DUI Penalties (2025)
| Consequence | Typical Range | Notes |
|---|---|---|
| Fines | $500-$10,000+ | Base fine plus assessments can triple it |
| Jail time | 0-6 months | Many states mandate minimum 48 hours |
| License suspension | 6-12 months | 48 states have administrative suspension |
| SR-22 insurance | 3-5 years | "High-risk" insurance costs 2-3x more |
| Ignition interlock | 6-12 months | Required in 27 states even for first offense |
| Probation | 1-5 years | Restrictions and monitoring |
The True Cost of a First DUI
| Category | Cost Range |
|---|---|
| Bail | $150-$2,500 |
| Towing and impound | $150-$300 |
| Legal fees | $2,000-$25,000 |
| Fines and fees | $1,500-$5,000 |
| Alcohol education | $200-$1,000 |
| Ignition interlock | $60-$200/month |
| Insurance increase | $1,000-$3,000/year |
| Lost wages | Varies |
| TOTAL | $10,000-$25,000+ |
Enhanced Penalties for High BAC
Most states impose harsher penalties for BAC of 0.15% or higher:
- Double the fines
- Mandatory jail time
- Longer license suspension
- Felony charges in some states
Beyond Financial Costs
- Criminal record (affects employment, housing, travel)
- Professional license consequences (doctors, lawyers, teachers)
- Custody implications in family court
- Immigration consequences (deportation risk)
- College admission and scholarship impacts
- Social stigma and relationship damage
Alcohol and the Body: What Really Happens
Understanding how alcohol affects your body helps explain why BAC matters.
The Alcohol Absorption Journey
| Stage | Timeline | What Happens |
|---|---|---|
| Mouth/Stomach | 0-15 min | ~20% absorbed through stomach lining |
| Small intestine | 15-60 min | ~80% absorbed; this is fastest |
| Bloodstream | 30-90 min | Alcohol reaches all organs including brain |
| Peak BAC | 30-90 min | Maximum BAC reached (varies by factors) |
| Metabolism | Ongoing | Liver processes 0.015% BAC/hour |
Why Food Matters So Much
Eating before drinking can reduce peak BAC by up to 50%:
- Food slows stomach emptying
- Alcohol reaches small intestine more slowly
- Liver has more time to process alcohol
- Peak BAC is lower and delayed
| Drinking Condition | Time to Peak BAC | Peak BAC Level |
|---|---|---|
| Empty stomach | 30 minutes | Higher |
| Light snack | 45-60 minutes | Moderate |
| Full meal | 60-90 minutes | Lower (~50% less) |
How Alcohol Affects the Brain
| BAC | Brain Region Affected | Result |
|---|---|---|
| 0.02% | Frontal lobe | Reduced inhibition, warmth |
| 0.05% | Cerebellum | Coordination impaired |
| 0.08% | Cerebral cortex | Judgment, reaction time impaired |
| 0.10% | Limbic system | Emotional instability |
| 0.15% | Medulla | Vital functions affected |
| 0.20%+ | Brain stem | Risk of coma, death |
Why Tolerance Doesn't Protect You
Tolerance makes you FEEL less drunk, but:
- BAC is exactly the same
- Impairment is exactly the same
- Danger while driving is exactly the same
- You're more likely to drink more (higher BAC)
- This makes tolerance MORE dangerous, not safer
Responsible Drinking: Practical Strategies
If you choose to drink alcohol, these evidence-based strategies can help minimize risk and avoid impaired driving.
Before You Drink
| Strategy | Why It Works |
|---|---|
| Eat a full meal | Reduces peak BAC by up to 50% |
| Plan transportation | Decide BEFORE you're impaired |
| Set a drink limit | Decide in advance, stick to it |
| Tell a friend your limit | Accountability helps |
| Download rideshare app | Remove barriers to safe ride |
While Drinking
| Strategy | Implementation |
|---|---|
| One drink per hour | Matches metabolism rate |
| Alternate with water | Slows consumption, reduces dehydration |
| Track your drinks | Use a phone note or app |
| Avoid shots/chugging | Causes BAC spikes |
| Choose lower-ABV drinks | Light beer vs. craft, etc. |
How to Stop Drinking for the Night
Signs it's time to stop:
- You've reached your pre-set limit
- You're feeling any effects (warmth, relaxation, etc.)
- You have somewhere to be in the next 10+ hours
- Someone suggests you've had enough
Looking Out for Others
If a friend has been drinking:
- Don't let them drive - period
- Offer to call them a ride or let them crash
- If they insist on driving, take their keys
- Don't let them walk alone at night while impaired
- Watch for signs of alcohol poisoning (confusion, vomiting, seizures, slow breathing)
When Not to Drink at All
| Situation | Why |
|---|---|
| Taking certain medications | Dangerous interactions |
| Operating machinery | Any impairment is dangerous |
| Pregnant or trying to conceive | No safe amount |
| History of alcohol use disorder | Risk of relapse |
| Need to drive within 6+ hours | May still be impaired |
| Under 21 | Illegal and developing brain |
Pro Tips
- 💡NEVER use this calculator to decide if you are safe to drive. If in doubt, don't drive. If you've had ANY alcohol, arrange alternative transportation.
- 💡Eat a substantial meal before drinking to slow alcohol absorption - this can reduce peak BAC by up to 50%.
- 💡Pace yourself: limit consumption to about one standard drink per hour, which matches your body's metabolism rate.
- 💡Alternate alcoholic drinks with water or non-alcoholic beverages. This slows consumption and keeps you hydrated.
- 💡Arrange transportation BEFORE you start drinking (designated driver, rideshare app, taxi). Don't leave this decision to your impaired self.
- 💡Count standard drinks accurately. Cocktails often contain 2-3 standard drinks. Craft beers and wines are often higher ABV than standard.
- 💡Remember that tolerance affects how drunk you FEEL, not your actual BAC or impairment. Experienced drinkers are just as impaired - they just don't realize it.
- 💡Beware the "morning after" - heavy drinking can leave you impaired well into the next day. A 0.15% BAC at midnight means you're still impaired at 6 AM.
- 💡Know that coffee, cold showers, and exercise do NOT sober you up. They may make you feel more alert, but your BAC and impairment remain the same.
- 💡Download a rideshare app before going out. When impaired, the barrier of "figuring it out" can lead to bad decisions.
- 💡Consider the true cost of a DUI: $10,000-$25,000+ in fines, fees, insurance, plus criminal record, job consequences, and potential jail time.
- 💡If someone you know has been drinking, don't let them drive. Take their keys, call them a ride, or let them sleep it off. You could save their life - or someone else's.
Frequently Asked Questions
This calculator provides estimates based on the Widmark formula, which is scientifically validated but has limitations. Actual BAC can vary by ±20% due to individual metabolism, food intake, medications, liver health, and other factors. This calculator should NEVER be used to determine if you are safe to drive. Professional breathalyzers and blood tests are the only accurate ways to measure BAC.
