What all-in budget are you planning, including design and permits?
Angi's 2026 typical range is $21,891 to $83,356; Zonda's midrange primary suite is $170,517.
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Addition Scope · Cost calculator
Home addition cost calculator
This calculator estimates the cost of an addition from added square footage, a finish tier, a route complexity level from bump-out to second story, and add-ons such as a bathroom, a kitchen tie-in, design and engineering, HVAC, permits and temporary housing. It is anchored to Angi's and HomeAdvisor's 2026 benchmarks and to Zonda's 2025 Cost vs. Value data.
Skip to the calculatorBase rates are anchored to: Angi, How Much Do Home Additions Cost (2026); HomeAdvisor, How Much Does a Home Addition Cost (2026); HomeAdvisor, How Much Does It Cost to Add a Second Story (2026); HomeGuide, Home Addition Cost (2026); HomeAdvisor, How Much Does It Cost to Build a Bump-Out Addition (2026); HomeAdvisor, How Much Does a Home Addition Cost (2026); CADTRI, Home Addition Permit: Drawings, Costs and Timeline (2026) (2026); Zonda, 2025 Cost vs. Value Report (2025).
By the numbers
Cost benchmarks behind the calculator
$21,891–$83,356
Typical U.S. home addition project range, $50,997 average (Angi, 2026)
Angi's addition cost guide, updated May 2026, puts the typical project between $21,891 and $83,356 with a $50,997 average. It is a mix of bump-outs, rooms and suites, not a price for a specified addition; building up, utility changes and existing-house work are priced separately.
Angi, How Much Do Home Additions Cost (2026)$51,000
HomeAdvisor's national average cost of a home addition
HomeAdvisor's guide (updated June 2026) puts additions at $21,896 to $83,355 with a $51,000 average and $80 to $210 per square foot for ground-level space. Room averages: bathroom $35,000, bedroom $62,500, kitchen $55,000, attic $40,000.
HomeAdvisor, How Much Does a Home Addition Cost (2026)$100–$300 / sq ft
Second-story additions cost $100–$300 per square foot on HomeAdvisor
HomeAdvisor's add-a-story guide (June 2026) puts most second stories at $100 to $300 per square foot, up to $500 with high-end materials, against $80 to $210 for building out, because the existing roof comes off and walls and foundation may need reinforcement. On a 1,000 sq ft second floor that is $100,000 to $300,000.
HomeAdvisor, How Much Does It Cost to Add a Second Story (2026)8 of 10
Eight of the ten best-returning 2025 projects were exterior replacements
Zonda's 38th Cost vs. Value Report covered 28 projects in 119 markets; 8 of the top 10 returns were exterior jobs and the Pacific and West South Central regions posted the strongest returns overall. Additions rank near the bottom, so plan them for living value.
Zonda / PR Newswire, 38th Annual Cost vs. Value Report release (2025)Angi's 2026 guide puts the typical addition at $21,891–$83,356; HomeAdvisor reports a $51,000 average with ground-level space at $80 to $210 per square foot and second stories at $100 to $300. Zonda's 2025 report prices a midrange primary suite at $170,517 and a midrange bathroom addition at $60,645. Those figures describe different projects, and this calculator lets you build yours and see which figure you are heading toward before a professional prices it.
The base rate is a mid-grade national figure per added square foot for ground-level space. Tiers move it for finish quality; route complexity moves it for foundation, roof and structural work; add-ons are flat amounts from published guides. Read the assumptions under the result, then take the figure to the estimate request.
How does the calculator build an addition estimate?
It starts with added square footage times a base of $160 per square foot, a mid-grade figure inside HomeAdvisor's $80 to $210 range for ground-level space and consistent with Angi's $50,997 average on a typical 320-square-foot room. The finish tier multiplies that: basic for standard windows, vinyl or fiber-cement siding and carpet or plank; mid-grade for better windows, matched siding, hardwood and tile; premium for custom millwork, stone veneer and designer fixtures. Route complexity then reflects the structure: a cantilevered bump-out, a ground-floor addition on a new foundation, or a second story with roof removal and reinforcement.
Add-ons are where addition budgets move, and each is priced from a named guide: a full bathroom at $35,000 (HomeAdvisor's room average), a kitchen tie-in at $15,000, design and engineering at $12,000 (inside HomeAdvisor's 5 to 20 percent architect range on a mid-sized project), a ductless mini-split or HVAC extension at $6,500, permits and drawings at $3,000 (CADTRI's 2026 figures), and temporary housing at $9,000 for second stories. A survey and any utility upgrades are noted in the assumptions rather than toggled.
| Input | What it represents | Anchor |
|---|---|---|
| Base rate | $160 per added sq ft, ground level, mid-grade | HomeAdvisor $80 to $210; Angi $50,997 average |
| Basic tier | 0.75x: standard windows, basic siding, carpet or plank | Low end of HomeAdvisor range |
| Premium tier | 1.4x: custom millwork, stone veneer, designer fixtures | Zonda upscale specifications |
| Second-story complexity | 1.8x: roof removal, reinforcement, temporary roof | HomeAdvisor $100 to $300; HomeGuide $300 to $500 per sq ft |
| Bathroom add-on | $35,000 flat | HomeAdvisor bathroom addition average |
| Design and engineering add-on | $12,000 flat | HomeAdvisor architect 5 to 20 percent |
What does the calculator leave out, and why?
It leaves out foundation underpinning, retaining walls, septic expansion, panel service upgrades, utility trenching for a detached ADU, and landscape or hardscape restoration, because each depends on conditions only a survey, an engineer or a site visit reveals. It leaves out furniture and appliances. And it uses national figures; coastal metros run higher and interior markets lower. Zonda's 2025 release noted that 8 of 10 best-returning projects were exterior replacements and that additions vary widely by market, so the regional swing is real.
The calculator also assumes the lot allows the footprint and the structure can carry it. If the route is a second story, the engineer's assessment can move the number in either direction; if the route is an ADU, the rules can change the size. Use the quiz to flag those conditions before relying on the figure, and the ADU page for the conversion-specific costs the tool treats as add-ons.
How should you use the result when comparing estimates?
Bring the inputs and the total to each site visit and ask the pro to walk through where their scope differs. A bid 20 to 30 percent under the calculator on the same route deserves a line-by-line look at the existing-house changes, the design fees and the HVAC; a bid far above it should point to a specific condition, such as frost-depth footings or a footing reinforcement, or to a local labor rate. Zonda's data show a midrange primary suite recovering 32.3%, so keep the total in proportion to the house and the street.
Then decide what to phase or drop. Houzz's 2025 study found secured home loans fund 18% of $50,000 to $200,000 projects, with savings at 81 percent. The MBA found 46% of home equity borrowers cited renovations, and Zonda's midrange bathroom addition recoups 53.3% of its cost. If the total lands above your comfort, the comparison pages show whether a bump-out or a conversion delivers most of the benefit, and the polls show what other homeowners cut first.
A worked example: 400 square feet, ground floor, with a bathroom
Take a common project: a 400-square-foot primary bedroom and bathroom off the rear of a one-story house, mid-grade finishes, on a new crawlspace foundation. The base is 400 times $160, or $64,000. The mid tier and ground-floor complexity leave it there. Add the bathroom at $35,000, design and engineering at $12,000, a mini-split at $6,500 and permits at $3,000, and the estimate reaches about $120,500. That sits below Zonda's $170,517 midrange primary suite, which is larger and includes a walk-in closet and higher finishes, and above HomeAdvisor's $62,500 bedroom average, which has no bath.
Now run the same 400 square feet as a second story: the complexity multiplier takes the base to $115,200, and with the same add-ons plus $9,000 of temporary housing the estimate passes $180,000. That is the build-out versus build-up decision in two numbers, and it matches the gap between HomeAdvisor's ground-level and second-story ranges. The same project in a coastal metro with frost-depth footings or seismic hold-downs would run higher, and only a site visit prices those.
| Line | Amount | Anchor |
|---|---|---|
| 400 sq ft at $160, mid tier, ground floor | $64,000 | HomeAdvisor $80 to $210 per sq ft |
| Full bathroom | $35,000 | HomeAdvisor bathroom addition average |
| Design and engineering | $12,000 | HomeAdvisor architect 5 to 20 percent |
| Mini-split, permits and drawings | $9,500 | CADTRI 2026 permit figures |
| Estimate, ground-floor suite | About $120,500 | Between HomeAdvisor bedroom average and Zonda midrange suite |
| Same suite as a second story, with temporary housing | Over $180,000 | HomeAdvisor $100 to $300 per sq ft |
Homeowner polls
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Cost calculator questions
Why is the calculator's base rate $160 per square foot?
Because it sits in the upper middle of HomeAdvisor's $80 to $210 range for ground-level additions and, on a typical 320-square-foot room, produces a figure near Angi's $50,997 project average. The tier multipliers move the effective rate across the whole published span, and the second-story multiplier reaches HomeAdvisor's $100 to $300 and the bottom of HomeGuide's $300 to $500 range for building up.
Does the estimate include design, engineering and permits?
As add-ons, so you can see them. HomeAdvisor reports architects at 5 to 20 percent of project cost; CADTRI's 2026 guide puts permit drawings at $1,200 to $2,100 and fees up to about $3,600. The calculator uses $12,000 for design and engineering and $3,000 for permits and drawings on a mid-sized project. Leave them toggled on; a proposal that omits them has not priced the project.
How much does adding a bathroom change the addition estimate?
It is the largest single add-on after the route. HomeAdvisor's bathroom addition average is $35,000, and Zonda's 2025 midrange bathroom addition specification is $60,645 with 53.3% recovery. The calculator uses $35,000. Our analysis of EIA's 2024 survey found 38.6% of homes have one full bathroom and 30.3% have a half bath, so check what you have first. If the bathroom is likely later but not now, ask for drains, vent and supply roughed in, which costs a fraction and avoids reopening the floor.
Why is the second-story multiplier 1.8 times the base?
Because building up removes the roof, adds a floor structure, reinforces walls and often footings, and builds under temporary weather protection. HomeAdvisor's per-square-foot range for second stories runs $100 to $300 against $80 to $210 for ground level, and HomeGuide's runs $300 to $500. A 1.8 multiplier on the $160 base lands at $288, inside both. The engineer's verdict can move a specific house well above or below it.
Should I select the temporary housing add-on for a ground-floor addition?
Usually not. A ground-floor addition is built weathertight before the connection to the house is cut, so most households stay. Select it for a second story, where the roof-off and framing phase makes the house uninhabitable for weeks to months, or for an addition that removes the only kitchen or bathroom. The $9,000 figure is a placeholder; local rents over two to four months set the real number.
How long will the project the calculator prices take?
The calculator assumes about 17 working days per 100 square feet at ground-floor complexity, which puts a 400-square-foot addition near three and a half months of construction, inside the two-to-four-month range typical for room additions. Second stories run longer. Add design and engineering of one to three months and plan review of two to eight weeks per CADTRI ahead of that. Bump-outs finish in one to four weeks per HomeAdvisor.
Can I use the calculator for an ADU or a garage conversion?
For a detached ADU, enter the unit's square footage at the ground-floor complexity and premium or mid tier, and add the bathroom, kitchen tie-in and design add-ons; the result should land near Zonda's $252 per square foot before utility trenching, which is not toggled. For a garage conversion, the shell already exists, so the result will run high; Angi's $150 to $400 per square foot range on the ADU page is the better anchor.
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Price a specific service
Service guideRoom AdditionsA room addition builds new ground-floor space on its own foundation, tied into the existing walls and roof, to add a bedroom, family room, kitchen extension, bathroom or primary suite.
Service guideSecond Story AdditionsA second-story addition builds a new floor on top of an existing house, either over the whole footprint or over part of it, after an engineer confirms the foundation and walls can carry the load.
Service guideADU & Garage ConversionsAn accessory dwelling unit is a second, self-contained living space on a single-family lot, built by converting a garage or basement, adding onto the house, or constructing a detached unit.
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