There are many different ways to estimate construction costs in a residential environment. An easy way to estimate costs is on a square foot basis. For example, say construction costs are $100/sq. ft. Now all you need to do is multiply this amount by the total square footage of your project. The only caveat for this method is that certain rooms cost more than others. Kitchens and baths cost
. more than bedrooms because of the appliance/finish factor. Also, the cost of construction can vary from region to region, so it is best to gain knowledge of the costs in your area. For more info on this, go here: http://www.building-cost.net/