Insulation Calculator
How many packs of insulation you need for a wall, loft or floor — from the area, thickness and coverage per pack — plus the volume in m³ or ft³.
Check the coverage per pack for the exact product and thickness you buy. Studs, rafters and openings are not deducted — measure the area to be insulated, or keep the waste allowance to cover offcuts.
About this tool
Enter the area to insulate, the insulation thickness, the coverage printed on the pack and a waste allowance. The calculator shows how many packs to buy (rounded up), the volume of insulation in cubic metres or cubic feet, and how much insulation one pack holds at that thickness. Works in metric (m², mm) and imperial (ft², inches) units.
Frequently asked questions
Multiply the length by the height (walls) or width (lofts and floors) to get the area, add a waste allowance, and divide by the coverage per pack for your thickness. Example: 40 m² + 5% = 42 m²; at 4 m² per pack that is 10.5, so buy 11 packs.
A pack holds a fixed volume of insulation, so thicker batts cover a smaller area. A pack covering 4 m² at 200 mm holds 4 × 0.2 = 0.8 m³; the same volume at 100 mm would cover 8 m². Always read the coverage for the exact thickness on the pack.
It depends on the building element and the U-value you need. Norway’s building regulations (TEK17 § 14-3) require U-values of at most 0.22 W/(m²·K) for external walls and 0.18 for roofs and floors. Use the U-value calculator to find the thickness for your target.
The calculator uses the area you enter. Insulation fills the space between studs, joists or rafters, so if you measure the whole wall the framing is included and you get a small margin; you can lower the waste allowance a little, or measure only the open bays.
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