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Insulation Calculator
Calculate insulation area coverage
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Result
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What this calculator does
Gives the insulation area to buy for a wall, from wall size and a waste allowance. For floors use the Flooring calculator for covering.
How to use it
- Enter wall width and height.
- Set the waste margin for trimming and fitting.
- Read the area in square meters.
Formula
Area m² = Width × Height × (1 + Waste Margin (%) / 100)
Formulas are shown in metric units, exactly as the calculator computes them. Imperial entries are converted to metric first. Waste is applied as a multiplier (1 + waste/100).
Areas are in m² and volumes in m³.
Variables
| Variable | Unit | Default |
|---|---|---|
| Width | m | 4 |
| Height | m | 2.5 |
| Waste Margin (%) | % | 10 |
Worked example
Using the default values of this calculator (Width = 4 m, Height = 2.5 m, Waste Margin (%) = 10 %), the calculator returns:
Area m² = 4 × 2.5 × (1 + 10 / 100)
- Insulation Area: 11 m²
Assumptions and limitations
- Only surface area is calculated: thickness and thermal performance (R or U value) are not considered.
- Framing members are not subtracted; check batt width against stud spacing.
Waste, rounding and buying
Insulation is sold in packs covering a stated area; round up. Compressed batts lose performance, so do not squash material to fit.
Frequently asked questions
- Does this tell me how thick the insulation must be?
- No. Thickness depends on local rules and the product datasheet.
- Is waste higher for insulation?
- Fitting around services and framing creates offcuts; adjust the percentage accordingly.