Insulation Calculator
Slabs, batts and whole packs from area, layers and product size.
How it works
The net surface is the gross area less openings. It is multiplied by the number of layers and the waste allowance, then divided by one slab or batt. Pieces are rounded up before they are grouped into whole packs, so package rounding is not hidden inside an average coverage figure.
The presets are real market package examples, not universal sizes. Product contents vary by R-value, thickness, facing, region and retailer, so replace all four package fields with the label on the material you will buy. This calculator estimates quantity; it does not select the insulation type or the code-required thermal resistance.
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How the Insulation Calculator works
An insulation calculator turns wall, floor or roof area into slabs or batts and whole packs. It allows for openings, multiple layers, the exact piece dimensions, package contents and a cutting allowance.
Count pieces before packs
Windows, doors and other uninsulated areas are removed from the gross surface first. Net area is multiplied by layers and waste, then divided by the area of one piece. That piece count is rounded up.
Only then is the result divided by the number of pieces in a pack and rounded up again. Going straight through a rounded pack-coverage label can under-order at a package boundary; the two-stage calculation preserves both physical constraints.
Thickness and layers change the material volume
One layer of 50 mm slabs gives 50 mm installed thickness; two layers give 100 mm and use twice the material area. The calculator also reports net installed volume, excluding the cutting allowance and surplus left after whole-pack rounding.
Required thickness is a design decision, not a quantity-calculator output. It depends on material conductivity, the full assembly, climate and applicable code. Use this page after the insulation type and target thermal performance have been specified.
Copy the exact package label
The metric presets follow current Knauf package examples: 610 × 1000 mm slabs contain 10 pieces at 50 mm and 5 at 100 mm, while a 610 × 1230 × 50 mm pack contains 16. They are useful starting points, not universal market standards.
Piece count changes with thickness and the format varies by manufacturer. Before ordering, replace width, length, thickness and pieces per pack with the exact label on the selected product; every package field remains editable.
FAQ
How many insulation packs cover 60 m²?expand_more
For 610 × 1000 × 50 mm slabs packed 10 at a time, 60 m² plus ten percent waste requires 66 m². One slab covers 0.61 m², so 109 slabs are needed: 11 whole packs containing 67.1 m².
Should windows and doors be subtracted?expand_more
Yes, where no insulation will be installed. Enter the combined area of large openings. Small penetrations and awkward junctions are usually better left in the area and handled by the cutting allowance.
How much insulation waste should I allow?expand_more
Five to ten percent is a common starting allowance for straight framing bays matched to the product width. Complicated roof geometry, many short bays and rigid boards that cannot reuse offcuts can need more. Site layout and the exact product control the final figure.