Flooring & Tiling calculator
Underlay Calculator
Estimate underlay packs or rolls from room dimensions, coverage per pack and an allowance for joins and trimming.
Estimate underlay packs or rolls from room dimensions, coverage per pack and an allowance for joins and trimming. Enter the project measurements first, then replace any default material or performance value with data for the product you intend to use. Check pack coverage and laying pattern carefully. Always round up to whole packs. Diagonal, herringbone or heavily cut layouts normally need more waste than a simple straight lay.
What you need to enter
The Underlay Calculator uses the following project information to calculate the result.
- Room length
- Room width
- Coverage per pack
- Waste (%)
Calculator result
Floor area, adjusted area, packs required
How the Underlay Calculator works
The Underlay Calculator estimates floor area, adjusted area, packs required from this relationship: length × width × allowance ÷ pack coverage. Because the page is designed for underlay packs or rolls beneath flooring, the calculation depends especially on pack coverage and laying pattern. Metric and imperial entries are normalised before the arithmetic so equivalent measurements produce equivalent results.
Underlay Calculator worked example
Underlay Calculator example: A 17.28 m² room with a 5% trimming allowance needs 18.14 m² of underlay. If the chosen rolls cover 10 m² each, buy 2 rolls; check roll dimensions as well as area so seams and offcuts are practical. The important sense-check is pack coverage and laying pattern, because that can move the real requirement away from the neat theoretical result.
Important calculation assumptions
For underlay packs or rolls beneath flooring, always round up to whole packs. Diagonal, herringbone or heavily cut layouts normally need more waste than a simple straight lay.
Frequently asked questions
What project details should I have ready for the Underlay Calculator?
Measure the finished room dimensions, enter the coverage printed on one pack and choose a waste allowance suited to the laying pattern. Those entries form the basis for estimating underlay packs or rolls beneath flooring.
What should I know about pack coverage and laying pattern before using the Underlay Calculator?
Always round up to whole packs. Diagonal, herringbone or heavily cut layouts normally need more waste than a simple straight lay. Treat the assumptions behind pack coverage and laying pattern as project-specific in the Underlay Calculator.
Should I order exactly the amount shown by the Underlay Calculator?
Use the Underlay Calculator to plan whole rolls or packs from floor area and product coverage. Check roll dimensions and seam layout separately, because an area-only pack count may leave awkward strips or unnecessary joints.