BAC Calculator - Educational Widmark Estimate Only

This is an educational Widmark estimate only. It is not legal advice. It cannot decide if it is safe or lawful to drive. It cannot tell you that you are “under the limit.” Impairment of attention, reaction time, and judgment begins at BACs that many people still call “small,” and rising absorption after the last drink means a later peak than the moment you stop pouring. Never drink and drive. Arrange a sober ride, public transit, or do not drink if you must operate a vehicle. We will not provide advice on beating a breathalyzer, hiding impairment, timing a police test, mouthwash tricks, hyperventilation games, or any other evasion. Do not use this calculator for those purposes.

Food in the stomach, beverage type, drinking pattern, sex- hormone and body-water differences, liver disease, and medications (including sedatives that add impairment without showing in a Widmark residual) all move real blood alcohol away from the classroom line. Illness can too. A forensic lab uses measured blood or a properly administered breath test under legal rules this website does not implement.

Other tools on this site (BMI, running pace, heart-rate zones) are also estimates. None of them clears you to drive after drinking.

Erik Widmark’s teaching form distributes a mass of ethanol into a fraction of body weight, then subtracts a constant elimination rate. On this page: BAC% = 100 × (alcohol_g / (weight_g × r)) − β × hours, floored at 0. Weight_g is kg × 1000. Alcohol mass is drinks × 14 grams (US standard drink) or a custom gram amount. Default r is 0.68 (male teaching value) or 0.55 (female teaching value); custom r is allowed. Default β is 0.015 %/hour; many texts mention a range near 0.010–0.020. Hours are counted from the first drink in this simplified model, not a full absorption curve.

Default check: 2 drinks × 14 g = 28 g. Weight 80 kg → 80,000 g. r = 0.68. 100 × (28 / (80,000 × 0.68)) = 100 × (28 / 54,400) = 0.05147%. Minus 0.015 × 2 = 0.030. Residual ≈ 0.0215% (displayed around 0.0215% or 0.021%). If elimination exceeds the distribution term, the display is 0, not a negative concentration.

1. Enter US standard drinks (14 g each) or custom ethanol grams. A UK unit (~8 g) and an Australian standard drink (~10 g) are not 14 g-convert mass yourself; this default is US 14 g.
2. Enter body weight in kilograms and choose r (0.68 / 0.55 / custom).
3. Enter hours since the first drink and β (default 0.015).
4. Read the residual as a study number only. Copy if you are checking arithmetic. Do not drive based on it. Inputs stay in this browser 30 days and are never uploaded.

A 5% beer, a 12% wine glass, and a 40% spirit shot are “one drink” only when the poured volume actually contains ~14 g ethanol. Heavy pours and high-ABV craft beer break the count. Custom grams exist for that reason. We will not tabulate “how many beers until X” as a driving table.

r is a lumped volume-of-distribution factor, not a measured total body water scan. Population means of 0.68 and 0.55 hide overlap between individuals. β is not a switch you can flip with coffee, cold showers, or exercise in a way this model will certify. Caffeine may make someone feel more awake while still impaired-another reason a web residual is not a go/no-go for a car.

Worked extras for arithmetic class only (still not driving advice): 0 drinks → 0. 1 drink, 80 kg male, 0 hours → 100 × (14/54400) ≈ 0.0257%. Same after 2 hours at β=0.015 → floored 0. 3 drinks, 70 kg, female r=0.55, 1 hour: alcohol 42 g; 100×(42/(70000×0.55))=0.1091; minus 0.015 → 0.094%. Those examples show sensitivity, not permission to drive.

Many places publish per se BAC thresholds for driving, often with lower limits for commercial drivers or young drivers. Those statutes, implied-consent rules, and penalties change and are not listed here on purpose: listing them next to a toy estimate invites the false inference that matching a number means you may drive. You must not use this page that way. If you need the law, read the statute or talk to a licensed attorney in that jurisdiction-not a calculator.

Breath devices in the field and evidential instruments in stations have operating procedures. We will not coach you on challenging, fooling, or waiting out those devices. A classroom 0.0215% is not a forensic result and is not a defense exhibit we will help you style.

If alcohol use is harming work, health, or relationships, seek qualified help (clinician, local support services). This page is not treatment.

We will not add a countdown until you are “legal,” a map of per se limits, a list of drinks-per-hour that “keep you under,” or a chart of tricks that change breath temperature or residual mouth alcohol. Those features would be used to plan driving after drinking. The educational remainder already has too much room for misuse; expanding it toward enforcement evasion is rejected.

We will not add a “gender-affirming r picker” that pretends a web form knows your body water, nor a pregnancy BAC mode. Ethanol and pregnancy are a clinical counseling topic, not a slider. We will not add a pediatric mode. We will not integrate a rideshare deep link as if that redeemed a residual that says 0.00 after a long β × hours subtraction- zero on this model can still be wrong if absorption is incomplete or if the drink count was a lie.

Mixing alcohol with other depressants (including some sleep aids and opioids) multiplies impairment in ways Widmark cannot see. The estimate can read “low” while the person is unsafe to bike, swim, or parent. Occupational bans (aviation, commercial driving) can be stricter than general road rules and still are not listed here.

If you are checking this page because a friend passed out, call emergency services rather than computing β. Unresponsive people need recovery-position first aid and professional care, not a 0.0215% classroom example. Alcohol poisoning is a medical emergency.

Storage uses a unique key for 30 days so a homework session can resume. That convenience is not anonymity against a device search. Delete site data if you shared a computer. Other calculators (due date, 1RM) also stay local; none of them interacts with this BAC number. Never drink and drive.

Search queries we will answer only as arithmetic: “BAC calculator two drinks 80 kg” is the 0.0215% default after two hours at β=0.015. “How long until BAC is zero” on this model is distribution/β, which for the default 0.05147/0.015 ≈ 3.4 hours from a hypothetical instantaneous absorption- which is not how drinking works, and is still not a driving countdown. We will not print a “sober at” clock in the result panel for that reason. If the residual is 0, you can still be impaired or still absorbing.

Standard-drink mismatches: a pint of 5% beer at 568 ml is more than 14 g ethanol (about 22 g). Two of those are not “two US drinks.” Use custom grams if you actually measured ABV and volume: grams ≈ volume_ml × (ABV%/100) × 0.789. That conversion is for homework accuracy, not for planning a drive. Never drink and drive.

This page reports mass/mass percent in the usual US teaching sense (grams of ethanol per 100 grams of blood, with the Widmark simplifications baked in). Some countries report grams per litre or milligrams per 100 millilitres. 0.0215% is not automatically 0.215 g/L unless you accept a density approximation that forensic labs treat more carefully than a website should. We will not ship a jurisdiction converter that looks like a legal instrument.

Breath alcohol and blood alcohol are related by a ratio that is itself a legal and scientific argument. This calculator does not output BrAC, does not apply a 2100:1 or 2300:1 partition, and will not help you “compare to a roadside device.” That would be a step toward the evasion use we refuse. Not legal advice. Cannot decide if it is safe to drive. Never drink and drive. Do not use this to beat a breathalyzer.

Zero drinks must yield zero on this model regardless of hours and β, because alcohol_g is 0. Nonzero drinks at 0 hours show only the distribution term. The default 2-hour wait is a homework story, not a recommended drinking pattern. We will not add a “one drink per hour” slogan because that slogan is widely misunderstood as a safety rule, which it is not.

If alcohol is a problem in your life, look to local health services rather than iterating r and β until a number feels comfortable. Comfortable numbers are how people talk themselves into keys. The 0.0215% default is a grading check for 28 g, 80 kg, 0.68, 2 h, 0.015-not a personality test.

4 US drinks, 80 kg male, 0 hours: 56 g; 100 × (56/54400) ≈ 0.1029%. After 3 hours at β=0.015, subtract 0.045 → ≈ 0.0579%. That is still not a driving OK. 2 drinks, 60 kg, female r=0.55, 2 hours: 100 × (28/(60000×0.55)) = 0.0848; minus 0.030 → 0.0548%. Same drinks, heavier body, larger r, and more hours all shrink the residual on paper while absorption, food, and medications still move the real value. Not legal advice. Never drink and drive.

Custom grams: 40 g ethanol, 90 kg, r=0.68, 1 hour, β=0.015: 100 × (40/(90000×0.68)) = 0.0654; minus 0.015 → 0.0504%. Changing β to 0.020 subtracts 0.020 instead of 0.015. The 0.010–0.020 teaching range is a reminder of uncertainty, not a knob for manufacturing a convenient zero. Flooring at 0 means a long wait prints 0 even if you are still drinking or still absorbing-another reason a zero residual is not a green light.

We will not add mouth-alcohol timing, burp warnings as evasion, or “best time to blow.” Those requests are refused. Do not use this page to beat a breathalyzer. Food, illness, and medications vary. Arrange a sober ride. The default 0.0215% exists so a grader can check 2 × 14 g, 80 kg, 0.68, 2 h, 0.015. Unique bac-split-track, 30-day localStorage, copy and clear-privacy is not legality.