Can this BAC calculator tell me whether I am safe to drive?

No, it cannot. This calculator provides a mathematical estimate based on the Widmark formula, but individual alcohol metabolism varies widely depending on food intake, medication, fatigue, genetics, liver health, and other factors. The only way to know your actual BAC is a certified breathalyzer or blood test. More importantly, even a BAC within a legal limit does not guarantee safe driving ability. After drinking any amount of alcohol, the safest decision is always not to drive.

What is the Widmark formula and how accurate is it?

The Widmark formula, developed by Swedish physician Erik MP Widmark in 1932, calculates an estimated BAC using three variables: total alcohol consumed (in grams), body weight, and a gender-specific distribution factor (r = 0.68 for males, 0.55 for females). It also subtracts a standard elimination rate of approximately 0.015 g/dL per hour. The formula is widely used in forensic and research contexts, but it is an approximation. Real-world BAC can differ by 20–30% or more due to individual variation in metabolism, stomach contents, drinking pace, and other physiological factors.

Why does biological sex affect BAC?

Biological sex affects BAC through two main mechanisms. First, females typically have a lower total body water percentage than males of the same weight, which means alcohol is distributed in a smaller volume, resulting in a higher BAC. The Widmark formula accounts for this with different distribution factors (r): 0.68 for males and 0.55 for females. Second, females on average have lower levels of alcohol dehydrogenase (ADH), the enzyme responsible for breaking down alcohol in the stomach, which means more alcohol enters the bloodstream. These are average physiological differences — individual variation exists.

Once the estimated time until 0% has passed, is it safe to drive?

No. The "estimated hours until 0%" is a rough metabolic calculation based on a fixed elimination rate (0.015 g/dL per hour). Individual alcohol metabolism varies widely depending on food intake, hydration, fatigue, medications, liver health, and genetics — actual clearance time can differ significantly. More importantly, the recovery of cognitive function and reaction time does not always align with reaching 0% BAC. This figure should never be used to decide when it is safe to drive. After drinking any amount of alcohol, the only safe decision is not to drive.

BAC Calculator (Blood Alcohol Concentration)

⚠️ This result cannot be used to determine whether it is safe to drive. Never drive after drinking alcohol.

이 결과는 운전 가능 여부를 판단하는 근거로 사용할 수 없습니다. 음주 후에는 절대 운전하지 마세요.

⚠️ This result cannot be used to determine whether it is safe to drive. Never drive after drinking alcohol.

이 결과는 운전 가능 여부를 판단하는 근거로 사용할 수 없습니다. 음주 후에는 절대 운전하지 마세요.

Your Information

Biological Sex

Used to determine the Widmark distribution factor (r).

Body Weight

Hours since you started drinking

Drinks Consumed

Drink 1

Type

ABV (%)

Volume (mL)

Estimated BAC (Blood Alcohol Concentration)

0.014%

= 0.14 g/L · 14.0 mg/dL

Estimated hours until 0%

0.9hrs

Time for BAC to reach 0% at the standard elimination rate of 0.015 g/dL/hr. This is a rough metabolic estimate only — not a clearance time for driving.

Widmark Formula

BAC (%) = [A × 100 / (W × r)] − (β × t)

A = alcohol (g), W = body weight (g), r = 0.68 (male) / 0.55 (female), β = 0.015 g/dL/hr, t = hours elapsed. Source: Widmark EMP, 1932.

This estimate is for informational reference only. Do not drive or operate machinery after consuming alcohol. The only safe BAC for driving is 0.000%.

BAC Level Reference

General physical effects at various BAC levels. For reference only — no threshold indicates safe driving. Source: NIAAA, CDC.

0.01–0.02%Subtle effects: mild warmth, slight mood lift. Most people feel little to no impairment.

0.03–0.05%Mild euphoria, reduced inhibitions, slight impairment of judgment and fine motor skills.

0.06–0.09%Noticeable impairment of balance, speech, vision, and reaction time. Judgment and self-control are reduced.

0.10–0.14%Significant coordination impairment, slurred speech, slower reaction time, impaired thinking and memory.

0.15–0.19%Gross motor impairment, nausea possible. Significantly reduced balance and judgment.

0.20–0.29%Severe impairment of all physical and mental functions. Nausea, vomiting, memory blackouts may occur.

0.30%+Potentially life-threatening. Risk of loss of consciousness, respiratory depression, and alcohol poisoning. Seek immediate medical help.

This calculator is for informational purposes only and does not constitute medical advice. Results are estimates based on general formulas. Always consult a qualified healthcare professional for health-related decisions.

About This Tool

Estimate your Blood Alcohol Concentration (BAC) using the Widmark formula. Enter your sex, weight, drinks consumed, and time elapsed to get an instant estimate — for informational reference only. Never use this to judge fitness to drive.

The calculation uses the Widmark formula (Widmark EMP, 1932), a standard method used in forensic and research contexts. It is an approximation — actual BAC is affected by food intake, medications, fatigue, genetic factors, and liver function, and may differ significantly from the calculated estimate.

Widmark Formula

BAC (%) = [A × 100 / (W × r)] − (β × t)

A = alcohol consumed (g), W = body weight (g), r = 0.68 (male) / 0.55 (female), β = 0.015 g/dL/hr, t = hours elapsed. Source: Widmark EMP, 1932.

How To Use

Enter your biological sex and weight — these are used for the Widmark distribution factor (r) and total body mass.
Set the hours elapsed since you started drinking — use the slider to select 0–12 hours.
Add each drink you consumed — select a preset to auto-fill the ABV, then adjust volume if needed.
Review the estimated BAC — the result is for informational reference only. Do not use this to judge whether driving is safe.

Example Calculation

Example: 80 kg male, 2 regular beers (355 mL × 5%), 2 hours elapsed

• Total alcohol = 355 mL × 2 × 5% × 0.789 g/mL ≈ 28.1 g

• Initial BAC = (28.1 × 100) / (80,000 × 0.68) ≈ 0.052%

• After 2 hours = 0.052 − (0.015 × 2) ≈ 0.022%

This figure is an estimate for reference only. Actual BAC can differ significantly based on food intake, drinking pace, and individual metabolic rate. Regardless of the calculated result, never drive after consuming alcohol.

Frequently Asked Questions

Can this BAC calculator tell me whether I am safe to drive?: No, it cannot. This calculator provides a mathematical estimate based on the Widmark formula, but individual alcohol metabolism varies widely depending on food intake, medication, fatigue, genetics, liver health, and other factors. The only way to know your actual BAC is a certified breathalyzer or blood test. More importantly, even a BAC within a legal limit does not guarantee safe driving ability. After drinking any amount of alcohol, the safest decision is always not to drive.
What is the Widmark formula and how accurate is it?: The Widmark formula, developed by Swedish physician Erik MP Widmark in 1932, calculates an estimated BAC using three variables: total alcohol consumed (in grams), body weight, and a gender-specific distribution factor (r = 0.68 for males, 0.55 for females). It also subtracts a standard elimination rate of approximately 0.015 g/dL per hour. The formula is widely used in forensic and research contexts, but it is an approximation. Real-world BAC can differ by 20–30% or more due to individual variation in metabolism, stomach contents, drinking pace, and other physiological factors.
Why does biological sex affect BAC?: Biological sex affects BAC through two main mechanisms. First, females typically have a lower total body water percentage than males of the same weight, which means alcohol is distributed in a smaller volume, resulting in a higher BAC. The Widmark formula accounts for this with different distribution factors (r): 0.68 for males and 0.55 for females. Second, females on average have lower levels of alcohol dehydrogenase (ADH), the enzyme responsible for breaking down alcohol in the stomach, which means more alcohol enters the bloodstream. These are average physiological differences — individual variation exists.
Once the estimated time until 0% has passed, is it safe to drive?: No. The "estimated hours until 0%" is a rough metabolic calculation based on a fixed elimination rate (0.015 g/dL per hour). Individual alcohol metabolism varies widely depending on food intake, hydration, fatigue, medications, liver health, and genetics — actual clearance time can differ significantly. More importantly, the recovery of cognitive function and reaction time does not always align with reaching 0% BAC. This figure should never be used to decide when it is safe to drive. After drinking any amount of alcohol, the only safe decision is not to drive.

Related Tools

Homebrew Gravity & ABV Calculator

Calculate estimated ABV from Original Gravity (OG) and Final Gravity (FG) using the standard homebrewing formula. Includes a dilution calculator to hit your target alcohol percentage. All calculations run in your browser — no login, no uploads.

Standard Drinks / Alcohol Units Calculator

Convert any drink's volume and ABV into standard drinks (US, UK, AU/SG, Canada) and pure alcohol grams. See how many units your drink contains according to your country's health guidelines — for reference only. All calculations run in your browser.

Hydrometer Temperature Correction Calculator

Correct your hydrometer reading for sample temperature. Enter your measured gravity, the actual sample temperature, and your hydrometer's calibration temperature to get an accurate specific gravity. Supports 59°F (15°C) and 68°F (20°C) calibration presets. All calculations run in your browser — no login, no uploads.