Blood Alcohol (BAC) Calculator
Estimate your blood alcohol concentration and understand Washington’s DUI limits. This is an educational estimate only.
Important: This calculator provides a rough estimate using the Widmark formula. Your actual BAC depends on many factors — metabolism, food, medications, health, and more — and can be higher than estimated. Never use this tool to decide whether it is safe or legal to drive. In Washington you can be arrested and convicted of DUI even with a BAC below 0.08%. This is not legal or medical advice.
Washington DUI legal limits
| Driver | Per se limit |
|---|---|
| Drivers 21 and over | 0.08% |
| Commercial drivers (CDL) | 0.04% |
| Drivers under 21 | 0.02% |
| Marijuana (THC) | 5 ng/mL |
A “per se” limit means you can be convicted of DUI based on that number alone. You can also be charged below these limits if an officer believes your driving was affected.
What affects your BAC?
- Body weight and composition
- Biological sex and metabolism
- How much and how fast you drank
- Whether you’ve eaten
- Medications and overall health
Charged with a DUI in the Seattle area? An experienced attorney can challenge the stop, the testing, and the evidence. Learn about DUI defense →
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