Underlay Calculator by Area
Work out how much underlay you need for a floor, wall or surface. Enter the length and width, the number of coats and a waste allowance. Based on…
8 of 8 free uses remaining today
Work out how much underlay you need for a floor, wall or surface. Enter the length and width, the number of coats and a waste allowance. Based on coverage of 15 m² per rolls of 15 m².
Worked example
Example calculated from the starting values. Enter your own values and press Calculate to get your result.
With the default inputs (length = 5 m, width = 4 m, coats or layers = 1, waste allowance = %10), the results are: area covered 20.00 m²; underlay needed 2 rolls of 15 m².
Quick reference: length vs result
Reference table based on the example values; it is not your calculation result.
| Length (m) | Area covered | Underlay needed |
|---|---|---|
| 2.5 | 10.00 m² | 1 rolls of 15 m² |
| 5 | 20.00 m² | 2 rolls of 15 m² |
| 10 | 40.00 m² | 3 rolls of 15 m² |
| 25 | 100.00 m² | 8 rolls of 15 m² |
| 50 | 200.00 m² | 15 rolls of 15 m² |
| 100 | 400.00 m² | 30 rolls of 15 m² |
Frequently asked questions
What formula does this calculator use?
Area covered = length × width; Underlay needed = ceil(length × width × coats ÷ cov × (1+waste ÷ 100)). Variables: length = length in m, width = width in m, coats = coats or layers, waste = waste allowance in %. Fixed values: cov = 15.
What do I need to enter?
You need length (m), width (m), coats or layers, waste allowance (%). Results update as you type.
What is an example result?
With the default inputs (length = 5 m, width = 4 m, coats or layers = 1, waste allowance = %10), the results are: area covered 20.00 m²; underlay needed 2 rolls of 15 m².
What coverage does this assume?
It assumes one rolls of 15 m² covers 15 m² per coat. Always check the coverage printed on your product, because it varies by brand and surface.
Related Tools
View allRoom Paint Calculator
Estimate how much paint you need for the walls of a room. Enter the room size, ceiling height, the area of doors and windows and the number of coats.
Paint Calculator by Area
Work out how much paint you need for a floor, wall or surface. Enter the length and width, the number of coats and a waste allowance. Based on…
Primer Calculator by Area
Work out how much primer you need for a floor, wall or surface. Enter the length and width, the number of coats and a waste allowance. Based on…
Floor sealer Calculator by Area
Work out how much floor sealer you need for a floor, wall or surface. Enter the length and width, the number of coats and a waste allowance. Based…