How Long Does It Take to Reach 0.00 BAC?
Your body eliminates alcohol at a fixed rate of approximately 0.015% BAC per hour. That means the math is straightforward: divide your current BAC by 0.015 and you get the hours until you reach zero. The hard part is knowing what your BAC actually is — and that is where a calculator becomes essential.
Use our free BAC calculator to get a personalised estimate based on your weight, sex, and drinks.
Calculate Your BAC Now →The 0.015% Per Hour Rule Explained
Alcohol is metabolised primarily in the liver by the enzyme alcohol dehydrogenase (ADH). Once ADH is saturated — which happens at blood alcohol concentrations above roughly 0.02% — metabolism follows zero-order kinetics: a fixed amount is eliminated per unit of time, regardless of how much alcohol is present.
That fixed rate is approximately 10–15 mg of alcohol per 100 mL of blood per hour, which translates to about 0.010–0.020% BAC per hour. The commonly used average is 0.015% per hour.
Why This Rate Doesn't Change
Unlike many biological processes, alcohol metabolism does not speed up in response to high blood alcohol concentrations. Your liver processes alcohol at the same rate whether your BAC is 0.05% or 0.25%. Drinking coffee, exercising, taking a cold shower, or eating food does not increase the rate. Only time works.
The Widmark Formula and Elimination
The Widmark formula calculates peak BAC from the grams of ethanol consumed, body weight, and a distribution factor (r). The elimination component simply subtracts 0.015 × hours_since_last_drink from the peak BAC. This gives a working estimate of BAC at any point in time after drinking.
Use our free BAC calculator to get a personalised estimate based on your weight, sex, and drinks.
Calculate Your BAC Now →How Long From Different BAC Levels to Zero
The table below shows how many hours it takes to reach key thresholds (0.05%, 0.02%, and 0.00%) from various starting BAC levels. All figures use the 0.015%/hr elimination rate.
| Starting BAC | Hours to 0.05% | Hours to 0.02% | Hours to 0.00% |
|---|---|---|---|
| 0.02% | 0 hrs | 0 hrs | 1.3 hrs |
| 0.04% | 0 hrs | 1.3 hrs | 2.7 hrs |
| 0.06% | 0.7 hrs | 2.7 hrs | 4.0 hrs |
| 0.08% | 2.0 hrs | 4.0 hrs | 5.3 hrs |
| 0.10% | 3.3 hrs | 5.3 hrs | 6.7 hrs |
| 0.12% | 4.7 hrs | 6.7 hrs | 8.0 hrs |
| 0.14% | 6.0 hrs | 8.0 hrs | 9.3 hrs |
| 0.16% | 7.3 hrs | 9.3 hrs | 10.7 hrs |
| 0.18% | 8.7 hrs | 10.7 hrs | 12.0 hrs |
| 0.20% | 10.0 hrs | 12.0 hrs | 13.3 hrs |
| 0.25% | 13.3 hrs | 15.3 hrs | 16.7 hrs |
| 0.30% | 16.7 hrs | 18.7 hrs | 20.0 hrs |
What Time Did You Stop Drinking? The Reverse Calculation
If you know your peak BAC and you know the current time, you can work backward: hours to zero = peak BAC ÷ 0.015. Add those hours to the time of your last drink to get your estimated sober time. For example: last drink at midnight, peak BAC 0.12% → 0.12 ÷ 0.015 = 8 hours → sober at approximately 8 a.m.
This is exactly what our morning-after BAC calculator does automatically.
Factors That Slightly Affect Elimination Rate
- Liver health: Chronic liver disease can significantly reduce elimination rate.
- Chronic alcohol use: Heavy drinkers may have slightly elevated ADH activity and metabolise alcohol 20–30% faster.
- Genetic variants: Some people have ADH or ALDH variants that alter metabolism speed.
- Medications: Some drugs (e.g. disulfiram) inhibit alcohol metabolism entirely.
For most healthy adults, 0.015%/hr is a reliable working estimate.
Why Coffee, Water, Food Don't Help
Hydration, food, and stimulants can influence how you feel — they do not change how fast your liver processes alcohol. Food before or during drinking slows absorption (lowering peak BAC), but food after drinking cannot pull alcohol back out of your bloodstream. Coffee increases alertness but does not reduce BAC. See our full article on whether you can speed up alcohol metabolism.
Use our free BAC calculator to get a personalised estimate based on your weight, sex, and drinks.
Calculate Your BAC Now →The Legal Limit Confusion: 0.08% Takes About 5.3 Hours
If your BAC is at the legal limit of 0.08%, it will take approximately 5.3 hours (0.08 ÷ 0.015) to reach 0.00%. If it is above 0.08%, it takes even longer to reach zero. Many people assume they can "sleep off" 4–5 drinks and be fine in the morning — but a 200 lb man who has 6 drinks may have a peak BAC around 0.08%, and still be at exactly the legal limit 5 hours later.
For the Widmark formula details, see our Widmark formula explained article.
FAQ
Does BAC drop faster if I drink a lot of water?
No. Hydration helps you feel better and prevents dehydration, but it does not change how fast your liver processes alcohol. Your BAC drops at the same rate regardless of water intake.
What is the fastest possible elimination rate?
Even in heavy chronic drinkers with enhanced ADH activity, the elimination rate rarely exceeds 0.02%/hr. Most adults should plan around 0.015%/hr to be conservative.
Is 0.00% BAC truly required to drive safely?
Legally, the limit is 0.08% in most US states (0.05% in Utah). However, impairment begins below 0.08%. For zero legal risk and maximum safety, wait until BAC reaches 0.00%.
Disclaimer: This article is for educational purposes only and does not constitute legal or medical advice. BAC estimates are approximations. Individual results vary based on body composition, food intake, health status, and other factors. Never drive if you feel impaired. When in doubt, don't drive.