Insulation · Project planning

Rigid Foam Insulation Calculator

Order sheets independently for each layer. Choose a layer count or calculate whole layers from a thermal target and the declared R of one sheet.

By Alish Gautam, Software Developer · Updated 4 October 2026 · Calculation methodology

Start with the editable example below. Dimensions retain their physical size when units change. Region sets currency labels without converting currencies; confirm entered quotes after changing region. Thermal inputs labeled US R retain that unit in every region.

Measured insulation surfaces

Use non-overlapping rectangles. Enter openings as area on the surface they interrupt.

Room / surface 1

Surface label

Surface length / wall run (ft)

Surface width / height (ft)

Uninsulated opening area (ft²)

Basic settings

Calculation modeChoose the estimating method.

Product settings

Product and system dimensions

Sheet width (ft)Editable arithmetic example. Replace with your project or product specification.

Sheet length (ft)Editable arithmetic example. Replace with your project or product specification.

Whole layersEditable arithmetic example. Replace with your project or product specification.

Product / specification referenceOptional supplier product name, chart revision or quote reference, saved in shared project state.

Advanced settings

Advanced planning settings

Purchase allowance (%)Planning allowance, not a code or industry requirement. Set zero to order the exact rounded takeoff.

Cost settings · USD

Optional quote prices

Price per purchased pack / unitOptional supplier quote in the selected currency. Blank omits cost.

Project takeoff

Whole packages round up. Allowance is separate from purchased surplus. Prices omit labor, delivery, tax and other items unless explicitly entered.

Gross measured area: 120 ft²
Opening / exclusion deductions: 0 ft²
Net requirement: 120 ft²
Allowance: 12 ft²
Planned requirement: 132 ft²
Unrounded package requirement: 4.125
Sheets per layer to buy: 5
Purchased coverage: 160 ft²
Surplus beyond planned requirement: 28 ft²
Layers: 1
Sheets per layer: 5
Total sheets to buy: 5

Supplier-ready material list

Sheets per layer to buy: 5
Rigid foam sheets: 5

Geometry / layout breakdown

Dimensions use the selected measurement system.
Surface	Material	Gross (ft²)	Net (ft²)
Room / surface 1	floor	120	120

Declared R belongs to the selected thickness and product. Joints, thermal bridging, fire protection, fastening and moisture detailing are outside the quantity estimate.

How it works

Sheets per layer = ceil(planned area / sheet area). Layers = ceil(target R / R per sheet) in target mode; total sheets = sheets per layer × layers.

Assumptions and limitations

Declared R belongs to the selected thickness and product. Joints, thermal bridging, fire protection, fastening and moisture detailing are outside the quantity estimate.

Whole packages round upward after the chosen allowance. Physical geometry and purchase reserve are separate. Manufacturer and project specifications override editable examples; the selected region does not establish a local code requirement.

Sources and boundaries

Natural Resources Canada: Keeping the Heat In — Section 3: Materials

Open the source · Web guidance; edition not stated · Reference checked 2026-10-04

Scope: Material and thermal-control guidance

Used for: R versus RSI terminology; Assembly-specific material considerations.

Does not establish: All products share one R per inch; Provincial code lookup.

Thermal conversion is a unit conversion; product resistance is an input.