Determine the size of balcony you want by measuring how far out you want it to come, and how wide you want it. Even a rough estimate will help you in your decision making.
Determine what type of balcony you want. For example, a small Juliet balcony, which barely protrudes past the door frame, costs less than a large, closed Maltese balcony.
Consider your building material options. Wood, wrought iron and concrete are commonly used for balconies. Choose what you think would look best with your home's exterior.
Contact several contractors and ask them for a price range for the type of balcony you want. Give them all the information you have gathered. Talk to at least three contractors so you can get a better sense of what prices are in your area. You will only get a general estimate of them until they have seen your home.
Research the costs for building permits and any other application fees required by your municipality. You can talk to municipality staff or they might have this information on your website.
Estimate the cost of your balcony by finding an average from the contractor quotes and adding the building fees to the figures.