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How to Use a Home Addition Calculator

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If you’re thinking about adding more space to your house, you’ll need to figure out how much it will cost. Many contractors and industry associations offer online home addition calculators that can help give you a ballpark estimate.

These tools let you factor in the square footage, materials, labor and rooms to estimate how much your addition will cost.

In this article:

What is a home addition?

A home addition involves expanding the size of an existing house. This could include adding a bedroom, bathroom or an entire story to a home. Homeowners often use additions as a way to add space or value to their homes.

While it may seem similar, a home addition is different from a remodel or an extension. With an addition, you’re adding an entirely new living area. On the other hand, a remodel simply means you’re updating a room, and an extension increases the size of an existing space.

What is the average cost of a home addition?

The cost of a home addition typically averages between $21,002 and $68,569, according to new data from HomeAdvisor, but varies widely based on the location, size and scope of the project. Experts also recommend adding some wiggle room in your home improvement budget in case there are unexpected hiccups during the project.

In most cases, contractors will quote a price based on the size of the addition, in square feet.

Home addition costs by square footage

In many cases, a standard home addition will cost somewhere between $80 and $200 per square foot.

Square feet added Typical cost
200 $16,000-$40,000
300 $24,000-$60,000
400 $32,000-$80,000
500 $40,000-$100,000
600 $48,000-$120,000
800 $64,000-$160,000
1,000 $80,000-$200,000
1,500 $120,000-$300,000
2,000 $160,000-$400,000

Home addition costs by room size

Costs can vary depending on how much new plumbing and electrical wiring involved, but the following can give you an idea. Figures come from home service companies HomeAdvisor and HomeGuide.

Room size Typical cost
10×10 $8,600-$15,500
10×12 $9,600-$24,000
10×20 $17,200-$31,600
12×12 $12,400-$22,300
16×16 $22,100-$39,700
20×20 $32,000-$80,000

Room addition costs

Costs will vary depending on the size of the addition, but here are some average costs of home additions to expect with the following rooms, according to HomeAdvisor and HomeGuide.

Addition Typical cost
Master suite $59,400-$96,500
Bedroom $10,300-$24,900
Bathroom $18,000-$47,000
Living/family room $34,400-$83,200
Mother-in-law suite $44,000-$100,000
Mudroom $2,880-$7,200
Kitchen $25,100-$43,400
Sunroom $8,100-$30,000

How a home addition calculator works

A home addition calculator typically asks you to input what type of project you’re working on and the size of your addition. Then it will ask you for your ZIP code or city, using that information to find the typical per square foot or overall cost from contractors in your location. Calculators will generally include fixed costs such as permitting as well as the type of building materials and extensiveness of electrical, plumbing or roofing needed.

Once you have an estimate, some calculator services can even connect you with contractors in your area.

Home additions that add the most value to your home

Second-story addition or a decked-out master suite? Not all home additions are created equally. When assessing how much value extra square footage can add to your home, these projects offer the most bang for your buck, according to Remodeling magazine’s latest “Cost vs. Value” report.

Addition Cost Resale value
Deck (wood) $13,333 $10,083
Bathroom $47,427 $28,726
Master suite $130,986 $77,785


Since additions can be pricey, private lenders and government entities like the U.S. Department of Housing and Urban Development offer loans to help finance them — including renovation loans or home improvement loans. Many of these loan programs expect that a home’s value will likely increase when the project is completed.


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