Home Addition Cost Calculator & Estimator
Estimate a home addition from the published low, typical, and high cost per square foot, then scale the labor share by a state’s construction wage index. Estimate (non-official) Building up or out? Try the room addition calculator or the second story addition calculator.
Estimated range at the U.S. median
$43,325 – $124,750
Typical estimate $87,850 ($219.63 per sq ft) Estimate (non-official)
| Hard cost | $40,000–$100,000 (typical $75,000) |
|---|---|
| Foundation adjustment | $0–$0 (typical $0) |
| Systems | $0–$0 (typical $0) |
| Design fees | $3,000–$20,000 (typical $10,313) |
| Permit | $325–$4,750 (typical $2,538) |
Your renovation budget
Set money aside for surprises found once work starts. Many homeowners keep 10–20% in reserve on remodels.
| Typical project estimate | – |
|---|---|
| Contingency reserve | – |
| Budget to plan for | – |
| If bids come in at the high end | – |
| Still to save or finance | – |
Get at least three written bids for the same scope, check licensing and insurance, and compare line items rather than totals. Homeowner planning guide
Contractor bid builder
The prefilled direct costs back out your overhead and profit from the typical market price above. Replace them with your own labour and material numbers to price the job.
| Direct job cost | – |
|---|---|
| Overhead | – |
| Profit | – |
| Contingency | – |
| Bid price | – |
| Gross margin / total markup | – |
| Compared with the market range | – |
Printable estimate details
Planning tool only. Confirm local code, permits, and your own costs before you send a bid. Contractor pricing guide
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Types of additions
Each rate is the researched range for that project type. Finish level in the calculator selects the low, typical, or high column. Estimate (non-official)
| Type | Low–typical–high per sq ft | Sources |
|---|---|---|
| Bump-out | $82.50–$200.00 (typical $141.25) Estimate (non-official) | |
| Single-room ground-floor addition | $100.00–$250.00 (typical $187.50) Estimate (non-official) | |
| Primary suite (bedroom + bath) | $297.03–$387.20 (typical $342.11) Estimate (non-official) | |
| Sources disagree. Large conflict: CVV national cost per sq ft is about 2-2.5x HomeGuide's. | ||
| Second-story addition | $150.00–$400.00 (typical $275.00) Estimate (non-official) | |
| Sources disagree. | ||
| Attached garage | $36.70–$90.00 (typical $63.35) Estimate (non-official) | |
| Sources disagree. Sources conflict (Angi ~$30 vs HomeGuide ~$43-$150 derived). Fixr $23,000-$45,000 (no size) not used. | ||
| Sunroom | $100.00–$350.00 (typical $225.00) Estimate (non-official) Single published source. | |
| In-law suite / attached ADU | $100.00–$275.00 (typical $187.50) Estimate (non-official) | |
20x20 home addition cost
A 20×20 addition is 400 sq ft. Using a mid-range room, a slab, no extra bathroom or kitchen, the architect fee on, and a construction wage index of 1.00 (the U.S. median), the range is $43,325 to $124,750, typical $87,850 ($219.63 per sq ft). Estimate (non-official) Choose a state in the calculator to replace the index of 1.00 with that state’s OEWS construction wage index.
Second story vs ground floor
A ground-floor room is typically $187.50 per sq ft ($100.00–$250.00). A second story is typically $275.00 per sq ft ($150.00–$400.00). Estimate (non-official) The second-story choice sets foundation work to none, because the new floor area is over the existing house. See the second story addition calculator or the room addition calculator for size-by-size examples.
Home addition cost per square foot
The type table above is the cost-per-square-foot guide. Bathroom and kitchen square footage inside the addition use their own rates instead of the type rate. The Census figures below are context for new houses, not additions.
| Census region | Median | Average |
|---|---|---|
| Midwest | $194.09 | $202.13 |
| Northeast | $179.30 | $246.26 |
| South | $157.30 | $179.96 |
| West | $176.87 | $213.85 |
Census figure is for new single-family houses, not additions. Relative standard errors are published in the CHARS workbook; this table shows the median and average only.
What affects addition costs in your state
Pick a state in the calculator. The wage table uses the OEWS median hourly wage for that state. The cost formula uses the construction-and-extraction wage index, not these trade rates directly.
| Trade | Median hourly |
|---|---|
| Carpenters | $29.12 |
| Construction laborers | $22.66 |
| Electricians | $30.38 |
| Plumbers | $30.67 |
| HVAC | $29.33 |
Questions
How much does a 20x20 home addition cost?
A 20 by 20 room is 400 sq ft. At the U.S. median construction wage (index 1.00), mid-range finish, slab foundation, no extra bath or kitchen, and the architect fee on, the range is $43,325 to $124,750 (typical $87,850, $219.63 per sq ft). Estimate (non-official). Pick a state to apply that state’s construction wage index.
How does a second-story addition compare with a ground-floor room?
The researched typical rate is $187.50 per sq ft for a ground-floor room and $275.00 per sq ft for a second story (ranges $100.00–$250.00 and $150.00–$400.00). Estimate (non-official). A second story does not add foundation area in this calculator.
Do the addition prices already include a foundation?
The guides are treated as including a basic slab. Choosing crawl, basement, or pier-and-beam adds the difference versus that slab, times local labor adjustment. Choosing none adds no foundation dollars. That slab assumption is editorial; the guides do not state it.
Why does my state change the addition estimate?
Only the labor share is scaled. With a labor share of 50%, the local factor is 1 minus that share plus that share times the state’s construction wage index (BLS OEWS, all construction and extraction occupations, versus the U.S. median).