The short answer
HomeGuide puts professionally installed spray foam at $1.50 to $5.00 per square foot of sprayed surface: $1.50 to $3.50 for open-cell and $3.00 to $5.00 for closed-cell. Those ranges mix jobs of different thickness, so the price you pay depends mostly on how many inches go on. At Angi's and HomeAdvisor's per-board-foot rates, each extra inch adds $0.60 to $1.60 per square foot for open-cell and $1.30 to $3.10 for closed-cell. Measure the surface being sprayed, not the home's floor area.
Updated October 2026. Prices are national planning estimates, not contractor quotes. Unless noted otherwise, square footage means the surface being sprayed, not your home’s floor area.
If you’re pricing a specific project, start with the table below, then use the thickness calculation to compare quotes on the same basis.
Quick Answer: Spray Foam Price per Square Foot
| Foam type | Typical installed cost per treated square foot | Typical use |
|---|---|---|
| Open-cell spray foam | $1.50–$3.50[1] | Above-grade walls, some conditioned attics and sound-sensitive interior assemblies |
| Closed-cell spray foam | $3.00–$5.00[1] | Rim joists, selected crawl spaces, metal buildings and assemblies requiring greater R-value per inch or lower vapor permeance |
| Both types, broad planning range | $1.50–$5.00[1] | Early project budgeting, before thickness and site conditions are known |
Source: HomeGuide’s spray foam insulation cost guide[1], updated December 2025, reports these installed surface-area ranges. These estimates should not be treated as fixed prices at every thickness.
Important: A contractor may quote $2 per board foot, not $2 per square foot of wall. At three inches thick, those represent very different totals. We explain the conversion below.
For a complete breakdown of project costs beyond area-based math, see our 2026 spray foam insulation cost guide.
How Much Does Spray Foam Cost by Project Size?
Here is what different treated surface areas cost if the job falls within the broad $1.50–$5.00[1] per square foot installed planning range.
| Surface area to be sprayed | Low estimate ($1.50/sq ft) | High estimate ($5/sq ft) |
|---|---|---|
| 100 sq ft | $150 | $500 |
| 250 sq ft | $375 | $1,250 |
| 500 sq ft | $750 | $2,500 |
| 750 sq ft | $1,125 | $3,750 |
| 1,000 sq ft | $1,500 | $5,000 |
| 1,200 sq ft | $1,800 | $6,000 |
| 1,500 sq ft | $2,250 | $7,500 |
| 2,000 sq ft | $3,000 | $10,000 |
| 2,500 sq ft | $3,750 | $12,500 |
| 3,000 sq ft | $4,500 | $15,000 |
Calculation: treated surface area × assumed installed cost per treated square foot. These are mathematical examples derived from a published national range, not observed quotes for each project size. Small jobs can cost substantially more per square foot because of contractor minimums.
A 2,000-square-foot house does not automatically need 2,000 square feet of spray foam. An attic roof deck, exterior walls and crawl space have different measurable surface areas. A quote should identify exactly which surfaces are included.
What Counts as Treated Square Footage?
Treated square footage measures the surfaces receiving insulation, such as a wall, underside of roof sheathing or crawl-space perimeter.
For a simple wall:
Wall surface area = wall length × wall height
A 40-foot-long by 8-foot-high wall is 320 square feet before deducting windows, doors or other excluded areas.
An attic with 1,000 square feet of floor space can have considerably more than 1,000 square feet of roof-deck area, particularly with a steep roof pitch and multiple slopes. Ask the installer for the measurement they used.
How Much Does Open-Cell Spray Foam Cost per Square Foot?
Open-cell spray foam typically costs about $1.50–$3.50[1] per treated square foot installed in published US national pricing guides. It is generally less expensive than closed-cell foam because it is lower-density and uses less raw material to fill a given cavity volume.
Open-cell foam typically delivers approximately R-3.6 to R-4.5[2] per inch, depending on the product and test method. Achieving a high overall R-value therefore commonly requires greater installed thickness than closed-cell foam.
| Treated area | At $1.50/sq ft | At $3.50/sq ft |
|---|---|---|
| 500 sq ft | $750 | $1,750 |
| 1,000 sq ft | $1,500 | $3,500 |
| 1,500 sq ft | $2,250 | $5,250 |
| 2,000 sq ft | $3,000 | $7,000 |
Illustrative totals using HomeGuide’s installed open-cell surface-area range; actual pricing depends on specified thickness and job conditions.
Open-cell isn’t automatically the cheapest choice for every assembly. If a project has limited cavity depth, a higher-R-value-per-inch material may be more suitable. Moisture and vapor control also matter.
Read our complete open-cell spray foam insulation guide for performance, applications and limitations.
How Much Does Closed-Cell Spray Foam Cost per Square Foot?
Closed-cell spray foam commonly costs about $3.00–$5.00[1] per treated square foot installed using HomeGuide’s national planning range. It is a denser, more rigid product with greater thermal resistance per inch and generally lower vapor permeance than open-cell foam.
Closed-cell products commonly deliver approximately R-5.8 to R-6.9[2] per inch, though you must use the selected manufacturer’s published data when specifying a project.
| Treated area | At $3.00/sq ft | At $5.00/sq ft |
|---|---|---|
| 500 sq ft | $1,500 | $2,500 |
| 1,000 sq ft | $3,000 | $5,000 |
| 1,500 sq ft | $4,500 | $7,500 |
| 2,000 sq ft | $6,000 | $10,000 |
Illustrative totals using HomeGuide’s installed closed-cell surface-area range. A thicker specification or difficult installation may exceed it.
Closed-cell foam can be useful for space-constrained cavities, but its lower permeability can reduce the drying potential of some building assemblies. That is an important design consideration around roof sheathing and existing moisture problems.
See the detailed closed-cell spray foam guide before choosing it for a particular part of your home.
Is Spray Foam Priced per Square Foot or per Board Foot?
Both. A board foot is one square foot of foam one inch thick[3], so a board-foot price only becomes a square-foot price once you know the thickness: price per square foot = price per board foot × inches. A $1.50-per-board-foot quote at 3 inches is $4.50 per square foot sprayed, not $1.50. Ask every contractor for area, thickness and total price so bids can be compared. The cost per board foot page has the formula and a board-feet table for common areas.
How Does Thickness Change the Price per Square Foot?
Thickness is often the missing variable in internet price charts.
Angi’s pricing report lists approximate installed board-foot ranges of $0.60–$1.60[4][5] for open-cell and $1.30–$3.10[4][5] for closed-cell foam. Multiplying those published ranges by thickness illustrates why prices per treated square foot rise as an application gets deeper.
| Foam and thickness | Illustrative cost per treated sq ft using board-foot rates |
|---|---|
| Open-cell, 1 inch | $0.60–$1.60 |
| Open-cell, 2 inches | $1.20–$3.20 |
| Open-cell, 3 inches | $1.80–$4.80 |
| Open-cell, 4 inches | $2.40–$6.40 |
| Open-cell, 5 inches | $3.00–$8.00 |
| Closed-cell, 1 inch | $1.30–$3.10 |
| Closed-cell, 2 inches | $2.60–$6.20 |
| Closed-cell, 3 inches | $3.90–$9.30 |
| Closed-cell, 4 inches | $5.20–$12.40 |
Calculated from Angi’s published installed board-foot price ranges. This is a mathematical model, not a promise that installers price thick applications linearly. Setup charges, pass limitations, material yield and project access affect real quotations.
Notice that the 3-inch and 4-inch closed-cell examples can exceed the general $3–$5[1]-per-square-foot headline range. That is not a contradiction: the general range mixes jobs with different depths; the thickness table prices a specific foam volume.
How Thick Should Spray Foam Be?
The correct depth comes from the required R-value and the building assembly, not the internet’s cheapest per-square-foot estimate.
An installer should determine:
- The climate zone and applicable energy-code requirements.
- Which surface forms the building’s thermal and air-control boundary.
- The manufacturer-specific R-value per inch.
- Moisture and vapor-control requirements for the assembly.
- Any required thermal or ignition barrier protection.
For example, 3 inches of an R-6.5-per-inch closed-cell product provides approximately R-19.5, before considering the overall thermal performance of framing and the assembly. A different product with a different tested R-value would produce a different result.
Don’t ask an installer to spray a set number of inches solely because an online article says that thickness is standard.
Worked Estimates for Common Projects
The examples below use stated assumptions to make the arithmetic transparent. They are not market quotes.
Example 1: 600 Square Feet of Open-Cell Foam
Assume 600 square feet of accessible wall surface and a quoted installed price of $2.50 per treated square foot at the specified depth.
600 × $2.50 = $1,500
Check whether the quote includes surface preparation, protection of electrical fixtures, masking, trimming, waste disposal and any code-required protective covering.
Example 2: 900 Square Feet of Closed-Cell Foam
Assume 900 square feet of treated surface and a fixed installed estimate of $4.50 per treated square foot at the contractor’s specified depth.
900 × $4.50 = $4,050
If another contractor uses board-foot pricing, get the specified depth and convert both estimates to a total installed price at the same R-value.
Example 3: 1,200-Square-Foot Surface, Priced by Board Foot
Assume 2 inches of closed-cell foam at a hypothetical quoted installed rate of $2.00 per board foot.
- Surface area: 1,200 sq ft
- Insulation volume: 1,200 × 2 = 2,400 board feet
- Total: 2,400 × $2.00 = $4,800
- Equivalent surface-area price: $4.00 per sq ft
This example also shows why the thickness must be written into the estimate.
What Affects the Installed Price?
Thickness, foam type, access, existing insulation removal, small-job minimums, moisture repairs, fire protection and local labor rates all move the price. HomeGuide reports minimum job fees of $1,000–$2,000 or more[1], which is why small jobs cost more per square foot. Each factor is explained in the main cost guide.
Is Spray Foam Worth the Price per Square Foot?
Spray foam is worth its higher price per square foot where it solves a real constraint: a shallow cavity that needs more R-value per inch, a hard-to-seal junction, or an assembly designed around its vapor behavior. For an accessible attic floor, air sealing plus conventional insulation is often cheaper. Compare options at the same performance target; see spray foam vs fiberglass and spray foam vs blown-in.
How to Get an Accurate Cost per Square Foot Quote
Get at least three itemized quotes for the same surfaces, foam product and thickness. A quote that says only “1,000 sq ft spray foam: $3,000” is incomplete: it doesn’t say whether that is two inches or five, or what R-value you get. Use the quote checklist in the main cost guide.
The Bottom Line
Use $1.50–$5.00[1] per treated square foot as a starting budget, not the final answer. To compare contractors properly, first establish what surface is being insulated, which foam is specified, how many inches will be installed, and what the total quote includes.
A square-foot price without a thickness is only half a price.
Compare spray foam insulation contractors to understand what a complete estimate should include.
Questions owners ask
How much does spray foam insulation cost per square foot installed?
National pricing guides commonly put spray foam at $1.50–$5.00 per treated square foot installed. Actual quotes vary by foam type, thickness, area size, accessibility and contractor minimums.
How much does open-cell spray foam cost per square foot?
HomeGuide reports $1.50–$3.50 per treated square foot installed as a broad US planning range. Confirm the specified depth and R-value before comparing a real bid.
How much does closed-cell spray foam cost per square foot?
A widely published US planning range is $3.00–$5.00 per treated square foot installed. Thicker closed-cell applications may exceed it because greater volume is required.
Is spray foam priced per square foot or board foot?
Both. Some contractors quote by treated surface area at a specified depth; others quote per board foot. A board foot equals one square foot at one inch thick, so you need the installed depth to translate between the units.
How much would it cost to spray foam 1,000 square feet?
At the broad $1.50–$5.00 per treated square foot planning range, the illustrative total is $1,500–$5,000. But first confirm that 1,000 square feet is the area of the surfaces to be sprayed and that the required thickness is included in the price.
Why does a small spray foam job cost so much per square foot?
Contractors may have minimum charges to cover crew travel, equipment setup, protective measures and cleanup. Those fixed costs are spread over fewer square feet on a small project.
Is a 2,000-square-foot house the same as 2,000 square feet of insulation?
No. House floor area and sprayed surface area are different measurements. Exterior wall surfaces, roof decks and crawl-space boundaries require their own takeoffs.
Sources
- How Much Does Spray Foam Insulation Cost?, HomeGuide. Accessed October 19, 2026. National consumer cost guide dated December 1, 2025. Installed cost per square foot and minimum job fees.
- Frequently Asked Questions, Spray Polyurethane Foam Alliance (SPFA). Accessed October 19, 2026. Industry trade association. Page metadata shows modified April 27, 2026. Typical density, R-value per inch, air-barrier thickness and vapor permeance ranges.
- Glossary, Spray Polyurethane Foam Alliance (SPFA). Accessed October 19, 2026. Industry trade association glossary; defines a board foot as 12 in. by 12 in. by 1 in.
- How Much Does Spray Foam Insulation Cost?, Angi. Accessed October 19, 2026. National consumer cost guide from a survey of Angi customers. No update date shown; title says "2025 Data". Its installed per-board-foot ranges match HomeAdvisor's page updated June 17, 2026.
- How Much Does Spray Foam Insulation Cost?, HomeAdvisor. Accessed October 19, 2026. National consumer cost guide, updated June 17, 2026. Installed cost per board foot; national ranges, not quotes.