Yes, and there are three ways to do it — each with a different level of risk and a different conversation with your lender.
More than the price difference between the two homes, which is where most move-up buyers underestimate. What comes out of your sale is reduced by the mortgage payout, any penalty, commission and GST on it, legal fees and adjustments. What goes into the purchase adds legal fees, Land Titles registration, moving and first-year costs.
Run it properly before you start looking: net proceeds calculator →. The gap between "the new house costs $200,000 more" and what you actually need is frequently substantial.
Buying before selling firm means committing to a purchase while your funding is still theoretical. If your home takes longer or sells for less than expected, you are the one absorbing it — and possibly reducing your price under time pressure, which is the worst position to negotiate from.
The order that goes wrong most often is buying unconditionally in a hurry because the perfect house appeared, then discovering the market is not as enthusiastic about yours as you assumed.