Actually you don't need a fancy on-line calculator IMHO. 

The banks used to use this very simple rule in determining how much they would loan you:

Your mortgage payment couldn't be more than 1/3 of your net take-home pay. 

Presumably they arrived at this calculation by looking at their data and concluding the likelihood of people defaulting was pretty low. 

I don't know if the banks are still using this rule. However I did read a while ago that the banks are now taking out CMHC mortgage insurance on all their mortgages so as to ensure they will always get all their money back if you do default. (And CMHC has recently put in a "Stress Test" for any mortgage they insure so that they don't have a flood of defaults to pay up on.)

Personally, I think the current prices in Toronto and Vancouver are unsustainable as, unless you already have a house that you can sell, most people cannot afford to pay the prices now being asked.