Drink and Drive Calculator Ontario

Drinking and driving is illegal in Ontario, and police can stop you for impaired driving if your blood alcohol content (BAC) exceeds legal limits. This calculator helps you estimate your BAC based on the number of drinks you've consumed and your personal characteristics.

How This Calculator Works

This drink and drive calculator for Ontario estimates your blood alcohol content (BAC) based on standard formulas used by law enforcement. You'll need to input:

Number of standard drinks consumed
Your weight in kilograms
Your gender
Time since your last drink

The calculator then applies the Widmark formula to estimate your BAC level. Remember that this is an estimate - actual BAC can vary based on individual metabolism and other factors.

Formula Used

The calculator uses the Widmark formula:

BAC = (A × 5.14 / W × r) - (B × t)

Where:

A = Total alcohol consumed (grams)
W = Body weight (kg)
r = Alcohol distribution ratio (0.68 for men, 0.55 for women)
B = Alcohol metabolism rate (0.015 for men, 0.017 for women)
t = Time since last drink (hours)

Legal Limits in Ontario

In Ontario, the legal limit for driving is:

80 mg of alcohol per 100 milliliters of blood (0.08% BAC)
350 mg of alcohol per 100 milliliters of breath (0.35% BAC)

If you're under 21 years old, the legal limit is zero - no amount of alcohol is permitted in your system while driving.

Note: These limits apply to all drivers in Ontario. Commercial drivers and those with a probationary license may have different limits.

How BAC Is Calculated

Blood alcohol content is calculated based on:

The number and type of alcoholic beverages consumed
Your body weight
Your gender (which affects alcohol distribution)
Time since your last drink

Standard drinks are defined as:

12 oz (355 ml) of beer (5% alcohol)
5 oz (148 ml) of wine (12% alcohol)
1.5 oz (44 ml) of 80-proof distilled spirits

Standard Drink Sizes
Beverage Type	Standard Drink Size	Alcohol Content
Beer	12 oz (355 ml)	5% alcohol
Wine	5 oz (148 ml)	12% alcohol
Distilled Spirits	1.5 oz (44 ml)	40% alcohol

Factors Affecting BAC

Several factors influence your BAC level:

Body weight: Larger individuals process alcohol more slowly
Gender: Women generally have lower BAC levels than men due to differences in body water content
Food intake: Eating before drinking slows alcohol absorption
Metabolism: Some people metabolize alcohol faster than others
Hydration: Being well-hydrated can affect alcohol distribution

These factors mean that the same number of drinks can result in different BAC levels for different people.

Penalties for Drink Driving in Ontario

Driving with a BAC over the legal limit in Ontario can result in:

Fines ranging from $200 to $1,000
License suspension
Vehicle impoundment
Court appearances and possible jail time

First-time offenders may receive a warning, but repeat offenders face increasingly severe penalties.

Important: Driving under the influence of any drug (including prescription medications) is also illegal in Ontario.

Frequently Asked Questions

What is the legal BAC limit in Ontario?: The legal limit is 80 mg of alcohol per 100 milliliters of blood (0.08% BAC).
How long does it take for alcohol to leave your system?: On average, it takes about one hour for your body to eliminate the alcohol from one standard drink. However, this can vary based on individual factors.
Can I drink coffee to sober up?: No. Coffee can make you feel more alert but does not reduce your BAC level.
What should I do if I've been drinking and need to drive?: If you've been drinking, the safest option is to arrange for a designated driver, take public transit, or use a ride-sharing service. Never drive if you're impaired.
Are there any exceptions to the drink driving laws?: No. In Ontario, it's illegal to drive with any detectable amount of alcohol in your system.