Spray foam calculator and insulation cost estimator.
List walls, rim joists and roof decks with the specified thickness. The calculator converts to board feet, adds overspray, divides by your set yield and prices the job, with R-value per inch you set from the product data sheet.
Send one plan set. See what the AI extracts and what it flags for review. No obligation.
- Board feet by area
- Sets from your yield
- Open- or closed-cell
1 · Areas area × thickness
2 · Product
3 · Prices
Live formula
Save your results
Copy these results, then add your approved sample files in the trial brief.
Estimates only. Check every default against your spec, supplier data and crew records before you bid.
Standard formulas, shown on the page.
Nothing hidden. These are the same steps an estimator runs on a takeoff sheet.
1. Board feet
A board foot is one square foot one inch thick. Multiply each area by its specified thickness in inches.
2. Overspray and trim
Spraying loses material to overspray, uneven passes and trimming back flush with studs. Add an allowance.
3. Sets
Divide by the theoretical yield per set from the manufacturer. Real yield depends on temperature, substrate and pass thickness, so compare against your own job records.
4. R-value and cost
R-value scales with thickness. Cost is material per board foot plus labor and equipment per square foot.
Every default is cited or editable.
Replace any of these with your spec, supplier data sheet or job-cost history. The calculator recalculates instantly.
| Input | Default | Source |
|---|---|---|
| Yield per set | 4,000 bd ft | Editable assumption for a closed-cell product; open-cell yields are much higher. Use the product data sheet. |
| R-value per inch | 6.5 | Editable assumption for closed-cell; open-cell is roughly half. Use the product's tested value. |
| Overspray & trim | 10% | Editable assumption |
| Prices | Blank | Enter your own |
Foam is one line. The estimate has more.
Thermal and ignition barriers
Code may require a thermal or ignition barrier over exposed foam. Check the spec and code path before you price exposed applications.
Assemblies vary by section
Wall sections, roof sections and rim conditions often call for different thicknesses or products. Run one row per assembly.
Access and protection
Masking, lift time, ventilation and re-occupancy windows add hours that board feet don't show.
From calculator to bid: get the quantities off the drawings.
Speed is easy to promise. Defensible numbers are the job, so RenderDraw keeps the estimator in control of every quantity that gets priced.
- Source on every row. Each quantity keeps its source sheet, location and reviewer decision.
- Lowest confidence first. The review queue shows the drawing tile with the detection highlighted and the extracted value.
- Uncertain items flagged, not hidden. Anything the AI can't confirm goes to the estimator rather than being guessed.
- Nothing priced before approval. Rows move on to pricing only after they are accepted.
Questions estimators ask
How do you calculate spray foam board feet?
Multiply the area in square feet by the thickness in inches. 1,000 sq ft at 2 inches is 2,000 board feet before overspray.
How many board feet in a set of spray foam?
It depends on the product and conditions. Closed-cell sets yield far fewer board feet than open-cell. Use the manufacturer's published yield and your own job history.
How do I estimate insulation cost?
Take off area by assembly and thickness, convert to board feet (or square feet for batts and board), add waste, and price material, labor, equipment and any barriers or prep the spec requires.
What R-value does spray foam give?
Roughly thickness × R-value per inch from the product data sheet. Closed-cell products are generally higher per inch than open-cell.
Can RenderDraw take off insulation from drawings?
Yes. RenderDraw proposes areas by wall and roof assembly from sections and plans, with the source sheet attached, for estimator review.
See what the AI reads on your own drawings.
Send one representative insulation plan set. RenderDraw reviews it and follows up with what the AI extracted and what it flagged for review. Your files remain private while the request is assessed, and there is no obligation.
- Upload wall sections, partition types, roof sections and the Division 07 insulation spec.
- RenderDraw reviews the set and the scope you want tested.
- We follow up with extracted quantities, flagged items and next steps.