BAC Estimator

Estimate Blood Alcohol Content using the Widmark formula.

⚠️ This is an estimate only. Actual BAC varies by individual. Never drive after drinking.

This tool is for educational purposes only and should not be used to determine fitness to drive or operate machinery.

Used for the Widmark body water constant (r factor).

Not sure? Use our Standard Drinks Calculator.

Estimated BAC

0.000

0 - 0.05
0.05 - 0.08
0.08+

Below 0.05

Legal

0.05 - 0.08

Warn Range

Above 0.08

Criminal

The Widmark Formula

BAC = (Drinks × 13.45) ÷ (Body Weight in grams × r) - (0.015 × Hours)

Where:

  • Drinks = number of Canadian standard drinks (13.45g alcohol each)
  • Body Weight = weight converted to grams
  • r = Widmark body water constant: 0.68 for males, 0.55 for females
  • 0.015 = average alcohol elimination rate per hour
  • Hours = time since first drink

Ontario BAC Legal Limits

Ontario has a two-tier system for impaired driving enforcement:

The 0.05 Warn Range

Under the Highway Traffic Act, drivers with a BAC between 0.05 and 0.08 (or who fail a Standard Field Sobriety Test) face escalating penalties:

  • First occurrence: immediate 7-day licence suspension, $250 penalty, and an 8-hour education course
  • Second occurrence: immediate 14-day suspension, $350 penalty, and a 16-hour treatment program
  • Third occurrence: immediate 30-day suspension, $450 penalty, a 16-hour treatment program, and an ignition interlock for 6 months

A licence reinstatement fee is also charged each time a licence is suspended. Drivers at 0.08 or higher, or who refuse or fail testing, also face an immediate 90-day licence suspension, a 7-day vehicle impoundment and a $550 penalty, in addition to any criminal charge. Ontario says some impaired driving penalties changed on July 1, 2026, so always check the current figures.

Source: Government of Ontario, Impaired driving (penalty figures verified October 30, 2026).

The 0.08 Criminal Limit

Under the Criminal Code of Canada, driving with a BAC of 0.08 or higher is a criminal offence. Penalties include:

  • First offence: Minimum $1,000 fine, 1-year driving prohibition
  • Second offence: Minimum 30 days in jail
  • Third offence: Minimum 120 days in jail
  • A criminal record that affects employment, travel, and insurance

Zero Tolerance

Ontario has zero tolerance (0.00 BAC) for:

  • Drivers aged 21 or under
  • Novice drivers (G1, G2, M1, M2 licence holders)
  • Commercial vehicle drivers

How Alcohol is Metabolized

Understanding alcohol metabolism is important for the SmartServe exam and for responsible service:

  1. Absorption: Alcohol enters the bloodstream through the stomach (20%) and small intestine (80%). Absorption takes 15-45 minutes on an empty stomach, longer with food.
  2. Distribution: Alcohol distributes throughout body water. People with more body water (generally males and larger individuals) will have a lower BAC from the same amount of alcohol.
  3. Metabolism: The liver breaks down about 90-95% of alcohol using the enzyme alcohol dehydrogenase (ADH). This occurs at a relatively fixed rate of approximately 0.015 BAC per hour (about one standard drink per hour).
  4. Elimination: The remaining 5-10% is eliminated through breath, sweat, and urine. This is why breathalyzers work.

Factors That Affect BAC

  • Body weight: Heavier individuals generally have a lower BAC from the same amount of alcohol
  • Body composition: Muscle tissue contains more water than fat, so more muscular individuals may have a lower BAC
  • Biological sex: Females typically have a higher BAC due to lower body water percentage and lower levels of ADH
  • Food: Eating before or while drinking slows absorption (but does not prevent intoxication)
  • Rate of drinking: Drinking faster increases peak BAC
  • Medications: Many medications interact with alcohol and can increase its effects
  • Tolerance: Chronic drinkers may not appear intoxicated at higher BAC levels, but their BAC is still elevated and their impairment is still real

Why This Matters for Servers

As a SmartServe-certified server, understanding BAC helps you:

  • Estimate how intoxicated a patron might be based on what they have consumed
  • Understand why different patrons react differently to the same amount of alcohol
  • Recognize that a patron who "looks fine" may still be over the legal limit
  • Make informed decisions about when to slow service or refuse further drinks
  • Explain to patrons why you are concerned about their consumption

Practice SmartServe Questions

Test your knowledge of BAC, intoxication signs, and responsible service.

Take Mock Exam Standard Drinks Calculator