How to use the insulation board count calculator
Give the wall its total run and height, and the roof and floor their width and length. The page works out each part area separately and lists them in a table. A window and door deduction comes off the wall, and once you add the insulation thickness, board size and waste percent you also get the volume and the board count. Leave a part blank if you do not have it.
Areas are simply dimensions multiplied, and the volume is the loss-included area times the thickness. The board count divides that area by the area of one board and rounds up only once, at the end. The page is current as of October 2026, and turning sizes into area is a definition rather than a standard.
A waste allowance was not confirmed in an authoritative source, so none is suggested and only your figure is applied. Thermal conductivity, U-value, condensation checks and code insulation levels are not covered. This calculator is for reference and does not replace design. Review by a qualified engineer is required.
Frequently asked questions
This page is built the other way round: it takes the dimensions of each part and works the area out for you, listing wall, roof and floor separately. If you already know an area, enter sizes that multiply to it.
No. Rounding up part by part stacks the roundings and inflates the count, so the loss-included total area is divided by the area of one board and rounded up only once at the end. The per-part rows stop at area.
No. The page covers dimensions through to area and quantity only. Thermal conductivity, U-value and condensation checks are not covered, and insulation performance needs product test data and a separate review.