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Insulation Quantity Calculator

Work out insulation quantity instantly with clear inputs, formula shown and shareable results.

About Insulation Quantity Calculator

Insulation quantity is area divided by pack coverage with a small cutting allowance. The thermal benefit is the R-value, thickness in metres divided by conductivity, so 100 mm of mineral wool at 0.035 W/m·K gives 2.86 m²·K/W. The U-value of that layer alone is the reciprocal.

Formulas

Quantity

Packs = ceil(area x 1.05 / coverage per pack)

Thermal resistance

R = thickness m / conductivity; U of the layer = 1 / R

Worked example

With the default values below, Insulation Quantity Calculator returns Rolls or packs required of 32. Change any input above and every figure here is recalculated in your browser.

Inputs used

Area to insulateminimum 0.1 m²
150 m²
Insulation thicknessminimum 5 mm
100 mm
Coverage per roll or packminimum 0.1 m²
5 m²
Thermal conductivityminimum 0.005 W/m·K
0.035 W/m·K

Results

Rolls or packs required
32
Thermal resistance achieved
2.857 m²·K/W
Insulation layer U-value
0.3500 W/m²·K
Insulation volume
15.00 m³

Step by step

  1. 1Values used
  2. 2Quantity
  3. 3Thermal resistance
  4. 4Rolls or packs required= 32
  5. 5Thermal resistance achieved= 2.857 m²·K/W
  6. 6Insulation layer U-value= 0.3500 W/m²·K
  7. 7Insulation volume= 15.00 m³

Assumptions and limits

  • The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 4 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

How is the Insulation Quantity figure worked out?

Packs = ceil(area x 1.05 / coverage per pack). Insulation quantity is area divided by pack coverage with a small cutting allowance.

Why is the real assembly U-value higher?

Framing members bridge the insulation, and air films and other layers add resistance. A framed wall with 15 percent timber fraction loses a noticeable share of the insulation's benefit.

What values do I need to enter?

This calculator takes 4 inputs: Area to insulate, Insulation thickness, Coverage per roll or pack, Thermal conductivity. The pre-filled defaults are a realistic worked example — replace them with your own site or project figures.

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