Unless you are planning to purchase all new furniture to put into your new home, knowing whether or not your current furniture fits can be a big deal. Chances are you want to know that even if you aren't in love with the property, just in case it turns out to be your backup option.
Will the couch fit? The oversized bed? That wonderful armoire Grandma left you?
I encourage you to take the time to measure rooms and consider layouts.
To aid in the process as you tour homes, I've put together a handout with some typical furniture (and appliance) dimensions (PDF). Feel free to put it to use!