Canada Import Duty on Alcohol

The duty you owe is a moving target, as it is subject to a national excise duty and to provincial taxes, and possibly GST on top of that. Your personal exemption also varies depending not only on the type of alcoholic beverage, but on the length of your trip. It is apparently enough of a headache that CBSA does not bother to include alcohol in its Duty and Taxes Estimator, which is too bad.

For Ontario, I would expect the Importing Beverage Alcohol guide from the LCBO to be most up-to-date, but note that the provincial taxes are based on where you enter Canada, not where you reside. If you go through customs in Vancouver, you would be subject to British Columbia taxes even if you live in Manitoba.

Toronto-based private immigration consultancy ImmiGroup estimates

In general, expect the cost of your beer and liquor to double and the price of your wine to increase by 60% once you've paid duties and taxes at the border.

There is a company called Border Buddy, aimed at commercial importation, which provides a web-based online calculator for calculating duties (note that they appear to be unaffiliated with the mobile apps going by the same name). I cannot vouch for its accuracy, but it seemed more optimistic, estimating around 18 CAD in duty on 50 CAD of whisky. The wild variance from ImmiGroup's estimate makes me think it is omitting some levy or another, however.