If you are trying to estimate your blood alcohol concentration (BAC), this calculator gives you a fast, educational estimate using a standard Widmark-style formula. It can help you understand how body weight, number of drinks, time, and biological sex influence BAC.
Important: This is an estimate only, not a legal or medical determination. If you have been drinking, do not drive.
What this blood alcohol calculator does
This tool estimates BAC as a percentage (for example, 0.08%). BAC is a measure of alcohol in your bloodstream. Even at lower levels, alcohol can reduce reaction time, judgment, coordination, and decision-making ability.
The calculation uses:
- Total alcohol consumed (via standard drinks)
- Body weight
- Biological sex constant (an average body-water distribution factor)
- Elapsed time, using a typical metabolic burn-off rate
How the formula works (in plain English)
A common BAC estimate in the U.S. is based on the Widmark approach:
- Each standard drink contributes about 0.6 fluid ounces of pure alcohol.
- The result is adjusted by a body-water constant (0.73 for male, 0.66 for female in this model).
- Alcohol elimination is approximated at 0.015 BAC per hour.
The final value is clamped at zero so it never shows a negative BAC.
Interpreting your result
Typical BAC ranges and effects
- 0.01–0.02%: Mild effects, subtle relaxation.
- 0.03–0.05%: Noticeable impairment in judgment and focus.
- 0.06–0.07%: Clear decline in coordination and response time.
- 0.08%+: In many places, this is at or above the legal driving limit.
- 0.15%+: Severe impairment and substantially increased risk.
Effects vary by person. Two people with the same estimated BAC may feel and perform differently.
Why BAC estimates can be wrong
No online calculator can perfectly predict your true BAC. Real-life variation is large. Key factors include:
- Food intake and meal timing
- Hydration, fatigue, stress, and medications
- Drinking speed and drink strength accuracy
- Individual metabolism and health conditions
- Measurement uncertainty in “standard drink” sizes
Safety first: practical guidance
If you drank, do this
- Use a designated driver, rideshare, or public transportation.
- Stop drinking early if you need to be alert later.
- Drink water and eat, but remember these do not “sober you up” instantly.
- Allow time. Metabolism is the primary way alcohol leaves the body.
If someone may have alcohol poisoning
Call emergency services right away if you notice confusion, vomiting, seizures, slowed breathing, or inability to wake the person.
Quick FAQ
Can coffee lower BAC?
No. Coffee may make someone feel more awake but does not reduce BAC.
Can I “speed up” alcohol metabolism?
Not reliably. Time is the major factor.
Is this calculator valid for legal decisions?
No. It is educational only and not legal advice or forensic evidence.