Blood Alcohol Concentration (BAC) Calculator

Why Monitoring BAC Matters

Blood Alcohol Concentration (BAC) measures the percentage of alcohol in your bloodstream. Monitoring BAC is important because it helps you:

• Stay Safe: Understand your level of impairment to avoid risky activities like driving
• Know Legal Limits: Ensure you're within legal driving limits to avoid legal consequences
• Make Informed Choices: Decide when to stop drinking or arrange alternative transportation
• Protect Your Health: Avoid excessive drinking that can lead to acute or chronic health issues
• Educate Yourself: Learn how alcohol affects your body based on various factors

How BAC is Calculated

The Widmark Formula

The calculator uses the Widmark formula to estimate BAC:

• Alcohol Consumed: Number of drinks × alcohol content (in grams)
• Body Water Constant: Males (0.68), Females (0.55) – reflects differences in body composition
• BAC Before Metabolism: (Alcohol in grams / (weight in grams × body water constant)) × 100
• Metabolism: Subtracts 0.015% per hour (average alcohol elimination rate)

Factors Affecting BAC

• Weight: Lighter individuals have higher BACs for the same amount of alcohol
• Gender: Females typically have higher BACs due to lower body water percentage
• Food Intake: Drinking on an empty stomach increases BAC faster
• Rate of Drinking: Faster consumption leads to higher BAC peaks
• Metabolism: Individual metabolic rates can vary, affecting alcohol elimination

Effects of BAC on the Body

0.02-0.03% (Low BAC)

• Slight relaxation, mild mood elevation
• Minimal impairment, slight decrease in reaction time
• Generally safe for most activities, but caution is advised

0.05-0.08% (Moderate BAC)

• Impaired judgment, reduced coordination, slower reaction times
• Difficulty focusing, exaggerated emotions
• Approaching or exceeding legal driving limits in many regions

0.08-0.15% (High BAC)

• Significant impairment in motor skills, slurred speech
• Poor balance, nausea, potential blackouts
• Unsafe to drive or operate machinery

0.15% and Above (Very High BAC)

• Severe intoxication, risk of alcohol poisoning
• Loss of consciousness, vomiting, memory loss
• Medical emergency possible—seek help immediately

Tips for Staying Safe

Plan Ahead

• Arrange a designated driver, taxi, or rideshare if you plan to drink
• Know your limits and monitor your drinks
• Drink water between alcoholic beverages to stay hydrated

Understand Standard Drinks

• One standard drink equals 14 grams of pure alcohol:
• 12 oz of beer (5% ABV)
• 5 oz of wine (12% ABV)
• 1.5 oz of liquor (40% ABV)

Avoid Risky Behaviors

• Never drive after drinking—BAC as low as 0.02% can impair driving
• Avoid binge drinking (4+ drinks for women, 5+ for men in 2 hours)
• Don’t mix alcohol with medications or drugs

Know When to Stop

• Stop drinking if you feel dizzy, nauseous, or overly impaired
• Seek medical help if someone shows signs of alcohol poisoning (confusion, vomiting, seizures, irregular breathing)
• Call emergency services if someone is unresponsive

Scientific References

• National Highway Traffic Safety Administration. (2021). Drunk Driving Overview.
• Centers for Disease Control and Prevention. (2022). Alcohol and Public Health: BAC.
• Widmark, E. M. P. (1932). Principles and Applications of Medicolegal Alcohol Determination.
• National Institute on Alcohol Abuse and Alcoholism. (2020). Understanding BAC.
• World Health Organization. (2018). Global Status Report on Alcohol and Health.