Online Breathalyzer Test
An online breathalyzer test estimates what a real breathalyzer device might read based on your weight, biological sex, number of drinks, drink type, and time elapsed. Enter your details in the panel on the left to get an instant virtual breathalyzer reading using the scientifically recognized Widmark formula.
What Is an Online Breathalyzer Test?
An online breathalyzer test is a digital tool that estimates your Blood Alcohol Content (BAC) — the same measurement a real breathalyzer device produces — using mathematical inputs about your body and drinking session. It applies the Widmark formula, the same foundational model used in forensic toxicology and medical research, to calculate an approximate breath alcohol reading expressed as a percentage.
Unlike a real breathalyzer device, an online test cannot directly measure alcohol in your breath. It produces a calculated estimate based on what you enter. The result is useful for understanding roughly where your BAC might fall, but it should never replace a physical breathalyzer test or be used to determine whether it is safe to drive. If you want to also calculate your blood alcohol content directly, use our blood alcohol calculator.
How the Online Breathalyzer Works
The Widmark Formula
This tool uses the Widmark formula to calculate an estimated BAC, which is also what a breathalyzer measures indirectly through breath alcohol content:
- A — Total pure alcohol in ounces (drinks × 0.6 oz per standard drink)
- W — Body weight in pounds
- r — Sex constant: 0.73 for males, 0.66 for females
- H — Hours since the first drink
- 5.14 — Conversion factor for alcohol density and volume
- 0.015 — Average hourly BAC elimination rate
Understanding the Fields
Each field in the breathalyzer form affects the estimated reading. Body weight determines the distribution volume of alcohol — heavier individuals generally show lower BAC readings from the same amount of alcohol. Biological sex affects how alcohol is distributed in body water. The number and type of drinks determines total pure alcohol consumed. Hours elapsed accounts for continuous metabolism at the standard rate of 0.015% per hour.
Reading Your Result
Your result is displayed as a three-decimal BAC percentage (e.g., 0.083%). This is the same format used by real breathalyzer devices and law enforcement. A reading of 0.08% or higher means the estimate is at or above the US legal driving limit. The tool also provides an estimated time to reach zero BAC based on the 0.015% per hour standard elimination rate.
Disclaimer - This Is an Estimate Only
This online breathalyzer test cannot replace a physical breathalyzer device. Real breathalyzers use electrochemical fuel cell sensors or infrared spectroscopy to measure actual alcohol concentration in exhaled breath. The Widmark formula used here assumes average metabolism rates, typical body water distribution, and standard alcohol content per drink — all of which vary significantly between individuals.
You should never use this estimate to decide whether to drive. Even if the estimate shows a BAC below 0.08%, your actual BAC may differ. Individual factors including food consumption, genetics, medications, and hydration can all cause real-world readings to diverge from calculated estimates. According to the National Highway Traffic Safety Administration impaired driving data, alcohol-impaired driving kills more than 10,000 people per year in the United States.
How Real Breathalyzers Work
Fuel Cell Sensors
Most law enforcement breathalyzers used at traffic stops use fuel cell sensor technology. When you exhale into the device, alcohol in your breath reacts with the platinum electrode inside the fuel cell, producing an electrical current proportional to the amount of ethanol present. This current is measured and converted to a BAC reading. Fuel cell breathalyzers are highly accurate and are accepted as legal evidence in court proceedings.
Infrared Spectroscopy
Evidentiary-grade breathalyzers used for official BAC testing in many jurisdictions use infrared spectroscopy. Ethanol molecules absorb infrared light at specific wavelengths, and the device measures how much light is absorbed to calculate the BAC. These instruments are laboratory-quality devices capable of producing readings accurate to within 0.001% BAC. The CDC alcohol and public health information notes that impairment begins well before drivers reach the legal limit.
Accuracy of Breathalyzer Devices
Certified breathalyzer devices are required to meet strict accuracy standards. In the US, the DOT requires breathalyzers to be accurate within plus or minus 0.005% BAC. Consumer-grade breathalyzers available for personal use are less accurate but still more reliable than mathematical estimates. Factors that can affect real breathalyzer accuracy include mouth alcohol from recent drinking, certain medical conditions (such as diabetes), and the presence of some chemicals in breath that can interfere with readings.
BAC Levels and Impairment
| BAC Level | Status | Effects on Body and Mind |
|---|---|---|
| 0.01–0.02% | Trace | Mild warmth or relaxation. Minimal to no visible impairment for most people. |
| 0.03–0.05% | Low | Lowered inhibitions, mild euphoria, slight impairment of judgment and fine motor skills. |
| 0.06–0.07% | Elevated | Reduced coordination and reaction time. Driving ability impaired for most individuals. |
| 0.08% | Legal limit (US) | Significant impairment of muscle coordination, judgment, and reaction time. DUI threshold in all US states. |
| 0.09–0.10% | Over limit | Slurred speech, slowed thinking, poor coordination, reduced balance. |
| 0.11–0.15% | High | Major loss of balance, nausea, severely impaired judgment and reaction time. |
| 0.16–0.20% | Very high | Dysphoria, nausea, possible vomiting, serious disorientation. |
| 0.20%+ | Danger | Loss of consciousness risk, alcohol poisoning, potential death. Medical emergency. |
Factors That Affect BAC Accuracy
The Widmark formula used in this online breathalyzer test is a reliable estimate, but real BAC can differ due to the following factors:
- Weight and body composition — Higher body weight means a larger distribution volume for alcohol, lowering BAC. Higher body fat percentage slightly raises BAC since fat tissue holds less water than muscle, concentrating alcohol in less body fluid.
- Biological sex — People assigned female at birth generally have less body water and lower levels of alcohol dehydrogenase in the stomach, leading to higher BAC from the same alcohol intake compared to males of the same weight.
- Food intake — Eating before or during drinking slows alcohol absorption significantly. A full meal can reduce peak BAC by 30–50% compared to drinking on an empty stomach.
- Metabolism rate — The standard elimination rate is 0.015% per hour, but individuals range from 0.01% to 0.03% based on genetics, liver health, and drinking history. According to the National Institute on Alcohol Abuse and Alcoholism, chronic heavy drinkers may metabolize alcohol faster due to enzyme induction.
- Medications — Many prescription and over-the-counter medications can interact with alcohol metabolism, amplifying its effects or altering elimination rate.
- Hydration — Dehydration concentrates alcohol in the bloodstream and can amplify impairment effects even at lower estimated BAC levels.
Legal BAC Limits
Standard 0.08% Limit
All 50 US states enforce a 0.08% BAC legal driving limit for adults aged 21 and over. A breathalyzer reading of 0.08% or higher provides grounds for a DUI or DWI charge. Some states also have administrative penalties beginning at 0.05%, such as automatic license suspension, even without criminal charges. At 0.08%, a driver has measurably impaired muscle coordination, judgment, and reaction time.
Zero Tolerance for Under 21
Every US state has a zero tolerance law for drivers under 21. The legal limit for underage drivers ranges from 0.00% to 0.02% depending on the state. Any measurable BAC on a breathalyzer test for an underage driver can result in license suspension, fines, and criminal charges. This stricter standard reflects both inexperienced driving combined with the additional impairment of any alcohol.
Commercial Driver Limits
Commercial drivers operating trucks, buses, or other commercial vehicles are held to a BAC limit of 0.04% — half the standard limit for private drivers. This lower threshold reflects the greater public safety responsibility and the longer stopping distances required by heavy vehicles. A breathalyzer reading above 0.04% during a commercial driving inspection results in immediate disqualification.
How Long Until You Are Sober?
The liver metabolizes alcohol at approximately 0.015% BAC per hour. This rate does not change regardless of how much water, coffee, food, or sleep you get after drinking. To calculate how long until your estimated BAC reaches zero, divide your BAC reading by 0.015. For example, an estimated BAC of 0.09% would take 6 hours to return to zero.
Alcohol can still be detected in breath for up to 24 hours after drinking even after BAC has returned to zero, because trace amounts remain in mucous membranes. For roadside testing purposes, BAC in breath and blood are considered equivalent. Nothing accelerates the elimination of alcohol from your system once consumed. For a full hour-by-hour breakdown of how your BAC declines over time, use our alcohol metabolism calculator.
Online Breathalyzer Test Examples
Example 1 - 200lb Male, 4 Beers, 3 Hours
A 200-pound male drinks 4 standard beers over 3 hours. Total pure alcohol: 4 × 0.6 = 2.4 oz. BAC = (2.4 × 5.14) ÷ (200 × 0.73) − (0.015 × 3) = 12.336 ÷ 146 − 0.045 = 0.0845 − 0.045 = 0.039%. This virtual breathalyzer reading comes in below the 0.08% legal limit. However, this person still has measurable alcohol and should not underestimate any impairment. You can test this scenario directly using the quick action button in the tool.
Example 2 - 130lb Female, 2 Wines, 1.5 Hours
A 130-pound female drinks 2 glasses of wine over 1.5 hours. Total pure alcohol: 2 × 0.6 = 1.2 oz. BAC = (1.2 × 5.14) ÷ (130 × 0.66) − (0.015 × 1.5) = 6.168 ÷ 85.8 − 0.0225 = 0.0719 − 0.0225 = 0.049%. This estimated breathalyzer reading is below the legal limit, but coordination and judgment are likely impaired. Driving should still be avoided at this level.
Frequently Asked Questions
Can an online breathalyzer test replace a real one?
No. An online breathalyzer test is an estimate based on the Widmark formula using inputs you provide. A real breathalyzer device measures the actual concentration of alcohol in your exhaled breath using electrochemical or infrared technology. Online tools cannot account for individual metabolism variation, food intake timing, medications, or body composition differences that affect real-world readings.
How accurate is this estimate?
The Widmark formula is a widely accepted scientific model but produces estimates rather than exact measurements. Research shows the formula can be accurate within 10-15% for most people under typical conditions. The estimate becomes less reliable if you have eaten recently, have unusual metabolism, or have taken medications that interact with alcohol.
What BAC level is legally drunk?
In the United States, a BAC of 0.08% or higher is the legal threshold for DUI charges for drivers aged 21 and over. Drivers under 21 face zero tolerance laws, with limits ranging from 0.00% to 0.02% depending on the state. Commercial drivers face a stricter limit of 0.04%.
How long after drinking can I pass a breathalyzer?
Your body metabolizes alcohol at approximately 0.015% BAC per hour. To estimate when you would pass a breathalyzer, divide your estimated BAC by 0.015. For example, a BAC of 0.09% would take approximately 6 hours to reach zero. Nothing speeds up this process — coffee, food, or exercise do not lower BAC faster.
Do breathalyzers detect all types of alcohol?
Yes. Breathalyzers detect ethanol, the alcohol found in all alcoholic beverages including beer, wine, and spirits. They do not differentiate between drink types. A standard breathalyzer reading represents the same ethanol content regardless of whether it came from beer, wine, or spirits.