Insulation Calculator

Area to insulate, m²

Layer thickness, mm

Pack volume, m³

Advanced options

Density, kg/m³

Result

Volume, m³8
Packs27
With a spare28
Mass, kg280
Thermal resistance R, m²·°C/W2.5

Counts the material and its effect

Insulation volume, number of packs, mass, and the thermal resistance the finished layer will deliver.

Insulation is sold by volume while walls are measured by area, so the volume comes from area times thickness. Divide by the pack volume printed on the bale and you have the order.

More useful than volume is thermal resistance, R. It equals thickness divided by conductivity, and it is what comparisons should be based on. A wall in a temperate climate wants around R 3, which is roughly 120 mm of mineral wool.

What this calculator shows

Volume and pack count, with a spare figure
Mass, which matters for framing and for carrying it upstairs
The layer's R-value, to compare against the requirement where you live

What to keep in mind

R is computed at 0.04 W/(m·K), typical for mineral wool and expanded polystyrene.
Thermal bridging through the frame is not modelled and cuts real performance by 10 to 20 percent.

FAQs

How thick should insulation be?

Around 120 to 150 mm of mineral wool for walls in a temperate climate, 200 for roofs, 100 for ground floors. Cold regions need half again as much.

What is thermal resistance?

A measure of how well the layer holds heat in, thickness divided by conductivity. The higher the R, the warmer the building and the smaller the heating bill.

Mineral wool or polystyrene?

Conductivity is almost identical. Wool breathes and does not burn but hates getting wet and needs a vapour barrier. Polystyrene is cheaper and water-tolerant but combustible and vapour-tight.

Can I insulate from the inside?

You can, but it is a poor second best: the dew point moves into the wall and moisture accumulates. If there is no alternative, a continuous vapour barrier is essential.

Worked example

Insulating a facade

Input: 80 m², 100 mm layer, 0.3 m³ packs

Output: 8 m³, 27 packs, R = 2.5

Note: R 2.5 is short of the roughly 3 a temperate climate wants. Going to 120 mm reaches R 3 and meets the requirement.

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Insulation Calculator

Result

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