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Guide · Blood alcohol

BAC and standard drinks, explained

Smart Serve expects you to understand standard drinks and what affects blood alcohol concentration (BAC). You don’t need to calculate anyone’s BAC at work, and you can’t. You do need to know how much alcohol is in what you pour, and why two guests can react very differently to the same drinks.

What one standard drink is

In Canada, one standard drink contains 17.05 mL (13.45 g) of pure alcohol. Each of these is one standard drink:

Health Canada / Canada’s Guidance on Alcohol and Health.
DrinkSizeAlcohol
Beer, cider or cooler341 mL (12 oz)5%
Wine142 mL (5 oz)12%
Spirits43 mL (1.5 oz)40%

Counting drinks that aren’t standard

Multiply the volume by the alcohol percentage, then divide by 17.05 mL. Some worked examples:

Our arithmetic from the standard drink definition.
What you pourPure alcoholStandard drinks
473 mL tall can, 5%473 × 0.05 = 23.7 mLAbout 1.4
341 mL craft beer, 10%341 × 0.10 = 34.1 mLAbout 2
86 mL double, 40% spirits86 × 0.40 = 34.4 mLAbout 2
250 mL glass of wine, 12%250 × 0.12 = 30 mLAbout 1.8

What affects BAC

Smart Serve’s BAC chart lists the factors that change how alcohol affects a person:

  • Body size and body fat: the same drinks raise BAC more in a smaller body.
  • Food: food slows the absorption of alcohol. The AGCO also notes it tends to slow the pace of drinking.
  • Medications and other drugs, including cannabis: they can add to the effects.
  • Metabolism, health, hydration, fitness and age.
  • Time: Smart Serve’s chart assumes the body clears roughly one standard drink an hour, and says real rates vary from person to person.

That’s why you watch the guest, not the count. Smart Serve says its chart is for education only and shouldn’t be the only basis for judging whether someone is intoxicated or able to drive.

Ontario’s driving limits

Ontario.ca, Impaired driving. Penalties changed on July 1, 2026; check ontario.ca for current amounts.
BACWhat it means in Ontario
Any alcoholNot allowed for drivers 21 and under, G1, G2, M1 and M2 drivers, and certain commercial drivers (zero tolerance)
0.05 to 0.079The “warn range”: immediate licence suspensions and penalties
0.08 or moreA criminal offence, with an immediate 90-day suspension

Drug-impaired driving, including cannabis or a mix of drugs and alcohol, carries the same penalties as alcohol-impaired driving.

Health guidance worth knowing

Canada’s Guidance on Alcohol and Health (2023) describes risk by drinks per week: 1–2 low, 3–6 moderate and 7 or more increasingly high. Ontario also requires every licensed establishment to post a sign warning that drinking during pregnancy can harm a baby.

Questions people ask

+What is the Smart Serve BAC chart?

It’s an educational tool on smartserve.ca that estimates BAC by sex, weight, number of standard drinks and time. Smart Serve says it’s for demonstration only and shouldn’t be used to decide whether someone can drive.

+How many standard drinks are in a tall can of beer?

A 473 mL can at 5% holds about 23.7 mL of pure alcohol, about 1.4 standard drinks.

+Is a 1 oz shot a standard drink?

Not by the health definition. A standard drink of 40% spirits is 43 mL (1.5 oz). Ontario’s minimum-price rule uses 29 mL (1 oz) as its standard spirits serving, which is a pricing rule, not a health measure.

+What is the legal BAC limit in Ontario?

0.08 is the criminal limit. From 0.05 to 0.079 is Ontario’s warn range with immediate suspensions. Drivers 21 and under and novice drivers must have zero alcohol.

Sources

Updated October 26, 2026. Not affiliated with Smart Serve Ontario or the Alcohol and Gaming Commission of Ontario (AGCO).

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