Free insulation calculator. Ceiling, wall and underfloor areas turned into the square metres to order at the R-value you specify, including 10% wastage.
This calculator turns ceiling, wall and underfloor areas into the quantity of insulation to order, at the R-value you are specifying. You supply the R-value. CostMate does not tell you what it should be, and the reason why is worth reading.
A 50 square metre ceiling comes out as 55.0 square metres of insulation to order, which includes CostMate's allowance for offcuts. Walls and underfloor work the same way, each with its own area.
The R-value is the one you specify.
The 6th Edition of H1 (Energy Efficiency), effective 27 November 2025, deleted the schedule method: the table you could look a number up in. What remains is a calculation method and a modelling method, and both of them trade insulation off between roof, wall, floor and glazing against a whole-building heat-loss target.
So there is no longer a per-element R-value to look up. A tool that printed one would be inventing an answer to a question the current document no longer asks that way.
Fill in the areas you are insulating (ceiling, walls, underfloor, or any combination): enter the area of each and the R-value you are specifying for it, and the page returns the quantity to order with CostMate's allowance of 10% added for wastage.
The R-value you enter is shown in the result. That is what a merchant needs, and it is worth having written down when someone asks later what went in.
The R-value for a given building is a design decision. Take it from your plans or your designer, and confirm product coverage with your supplier, before you order.