If you are deciding whether you are safe to drive after alcohol, the safest answer is simple: do not drive after drinking. Use this calculator as an educational estimate only, not a guarantee. Real impairment can occur before legal limits, and legal limits vary by country, state, and license type.
Estimated BAC Calculator
Enter your details to estimate blood alcohol concentration (BAC). This tool assumes U.S. standard drinks (0.6 fl oz pure alcohol each).
Important: Coffee, cold air, showers, and exercise do not reliably lower BAC. Only time does.
How this drinks calculator works
This calculator uses a simplified Widmark-style formula to estimate BAC from your body weight, number of standard drinks, and elapsed time. It also applies a typical alcohol elimination rate of 0.015 BAC per hour.
- Standard drink: 0.6 fluid ounces (14 g) of pure alcohol
- Distribution ratio (r): varies by sex category
- Metabolism: estimated average, not individualized
What counts as one standard drink?
| Drink Type | Typical Amount | Approx. ABV |
|---|---|---|
| Beer | 12 oz | 5% |
| Wine | 5 oz | 12% |
| Spirits (shot) | 1.5 oz | 40% |
Why estimates can be wrong
No online tool can tell your exact impairment. Two people with the same inputs can have different BAC and different reaction time. Many factors matter:
- Food intake before and during drinking
- Medication interactions
- Sleep deprivation and fatigue
- Hydration status and health conditions
- Drink strength errors (especially mixed drinks and tall pours)
That is why this page treats the number as a risk estimate, not permission to drive.
BAC ranges and practical meaning
0.01% to 0.04%
Mild impairment may begin: reduced focus, divided attention, and reaction speed changes.
0.05% to 0.07%
Noticeable impairment is common. Many countries set legal limits at 0.05% because crash risk rises in this range.
0.08% and above
In many regions this is above legal driving limits and associated with substantially higher crash risk. Penalties can include fines, license suspension, and criminal consequences.
Safer choices if you have been drinking
- Use a rideshare, taxi, or public transit.
- Designate a sober driver before events.
- Stay overnight when possible.
- If a friend has been drinking, help arrange a safe ride.
Bottom line
The smartest strategy is straightforward: if alcohol is involved, do not drive. This calculator is useful for education and planning, but it should always push your decision toward caution and safety.