One of the most important steps in planning and budgeting for a home addition is getting reliable home addition estimates.  Early estimates help you decide if you can afford to build the addition to your home you are considering.  Whether you are adding on because of another child in the family or parents moving in with you, reliable preliminary estimates are the basis for making a decision about whether to pursue your plans. 

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There are several ways to get a preliminary estimate of the cost of a home addition.  One is to browse remodeling magazines and websites for charts outlining the average cost for certain types of home remodeling or additions projects.  Another way is to contact your local builders association or a contractor to get an estimate based on the average cost per square foot to build an addition. 


There are, however, several things to consider before trusting these ballpark estimates. 

  • The cost per square foot will vary according to the type of room you are adding. For example, the cost per square foot for a bathroom will be considerably higher than the cost per square foot to add a den. Contractor Selection Workbook

  • Construction costs vary somewhat by location.

  • Construction cost per square foot also varies according to the quality of workmanship you expect.

  • Construction cost per square foot varies according to the quality of the materials you select for the project.

  • Costs can also vary with the seasons. For example, many contractors charge as much as 15% less for jobs scheduled during their slow season.

There are also other factors that affect the accuracy of a preliminary cost estimate for a home addition.  These include:

  • Plans for an economy, average or custom addition.

  • Plans for a larger-than-average addition (or smaller-than-average).

  • Steps you will take to reduce costs, such as shopping for materials or picking up materials (to avoid delivery costs).

  • Whether you will manage the project or have a general contractor or project manager in charge.

  • What if any work you will do on the project.

  • Whether you will have plans drawn by an architect, a home designer, or your contractor.

Even as complicated as this sounds, there are a number on online or software construction cost calculators that are commonly used to get a preliminary estimate on a home addition project. It is, however, important to keep in mind that the accuracy of the estimate depends on the information requested and considered by the cost calculator. 101 Ways to Save Money When by by Dan Fritschen

Clearly no electronic calculator will be able to give you an instant estimate that is 100% accurate. This depends upon far too many variables to be readily programmed. This is the estimate you will get from the contractors you consider for your project when you decide on your budget and your expectations.  But it is possible to find and use (free) an online calculator that considers more of the variables than other calculators, and is thus able to give you a more reliable estimate. These are the state-of-the-art calculators at and 


From deciding whether you are better off to remodel/add to your current home or move to another home to providing a reliable preliminary estimate of the cost of your project, these are the best calculators available.  In addition to asking you the obvious questions about the size of your addition and the quality of materials and workmanship you expect in your project, these calculators will also ask you for your zip code and ask about how involved you will be in various aspects of the project. They will also ask you whether you will use professionals who are more or less expensive for various parts of planning and building your addition.  When you are ready to get initial home addition estimates and evaluate the cost impact of various choices, these are the most reliable calculators available to help you make informed decisions.

Here are several related articles you might want to read:
What Does It Cost to Remodel?
The Best Way to Pay for a Remodel
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