Insulation quantity calculator
Estimate insulation packs and roll length from area and pack coverage; 25 m² with 5 % waste and 5.4 m² rolls needs 5 rolls.
- Runs in your browser
- No upload
- Instant result
Quantity estimate only. This does not approve structural safety, load capacity, drainage, fire resistance or building-code compliance. Verify the design and local requirements with a qualified professional. Purchase quantities round up to whole packs.
Assumptions & formula
Formula and assumptions
w = Waste allowance/100; N=ceil(S(1+w)/packCoverage); L=S(1+w)/width
The prefilled values are editable examples, not product specifications. Enter your supplier’s yield, density, coverage and packaging values, and add an allowance for overlaps, compaction and cuts where needed.
Purchase counts use the exact entered decimals and unit factors, without a rounding tolerance that could discard a real remainder. π and irrational square roots use enclosing bounds; ambiguous counts produce an error. Counts must be safe integers.
Results
Enter values and press Calculate to see the result here.
How to use this calculator
- Set inputs and units
Enter the net rectangles, the insulation label, the manufacturer’s pack coverage and the roll width, and set the allowance separately.
- Calculate
Check this worked example: 5×2 m=10 m²; packCoverage8 m²,rollWidth0.5 m,waste0% →packs2,purchasedArea16 m²,equivalentLength20 m
- Results
The equivalent roll length is the required area divided by the width. It isn't necessarily the length inside the rounded number of packs you buy.
Questions and limits
Does quantity determine thermal performance?
No. Thickness, conductivity, thermal bridges and assembly details are not used to calculate U or R values here.
Which input errors should I correct?
Use positive pack coverage and roll width. Tell m² per pack apart from the linear meters of a roll.
What does this calculation leave out?
No assessment of thermal performance, condensation, fire rating or compliance with building codes. Use the product and system specifications separately.