Insulation Board Count
Divide the total area by the area of one board. A cutting-and-overlap margin of around 10% is added.
Your numbers
Sheets needed
41
Area of one sheet
1.62m²
Formula
Sheets needed = Area × (1+Waste allowance÷100) ÷ (Sheet width (mm)÷1000 × Sheet length (mm)÷1000)
XPS and EPS insulation come in slightly different standard sizes — check the product spec before ordering.
What to enter
| Input | Default | Accepted range |
|---|---|---|
| Area (m²)The space a shape covers — length squared. | 60 | 1 and up |
| Sheet width (mm) (mm)The short side of one sheet — it sets how often joints fall. | 900 | 100 and up |
| Sheet length (mm) (mm)The long side of one sheet, usually chosen to match the ceiling height. | 1,800 | 100 and up |
| Waste allowance (%)The extra bought to cover breakage and offcuts. | 10 | 0 ~ 30 |
Step by step
Quick reference table
Results when only Area (m²) changes and everything else stays put.
| Area (m²) | Sheets needed | Area of one sheet (m²) |
|---|---|---|
| 30 | 21 | 1.62 |
| 45 | 31 | 1.62 |
| 60 | 41 | 1.62 |
| 90 | 62 | 1.62 |
| 120 | 82 | 1.62 |
What each result means
| Result | At default values |
|---|---|
| Sheets neededSheets to buy; they are not cut down at the till, so this rounds up. | 41 |
| Area of one sheet (m²)The width times length of a single sheet. | 1.62 |
Common mistakes
XPS and EPS insulation come in slightly different standard sizes — check the product spec before ordering.
Glossary
- Area
- The space a shape covers — length squared.
- Sheet width (mm)
- The short side of one sheet — it sets how often joints fall.
- Sheet length (mm)
- The long side of one sheet, usually chosen to match the ceiling height.
- Waste allowance
- The extra bought to cover breakage and offcuts.
- Sheets needed
- Sheets to buy; they are not cut down at the till, so this rounds up.
- Area of one sheet
- The width times length of a single sheet.
Frequently asked questions
QHow is Insulation Board Count calculated?
Sheets needed = Area × (1+Waste allowance÷100) ÷ (Sheet width (mm)÷1000 × Sheet length (mm)÷1000) — Divide the total area by the area of one board. A cutting-and-overlap margin of around 10% is added.
QCan you walk through an example?
With Area 60m², Sheet width (mm) 900mm, Sheet length (mm) 1,800mm, Waste allowance 10%, the answer is Sheets needed 41.
QWhat do I need to enter?
Enter Area, Sheet width (mm), Sheet length (mm), Waste allowance. The result recalculates as you type, and an empty box counts as zero.
QHow much does the answer move if I change a number?
Changing only Area (m²) moves the answer to Area (m²) 30 → Sheets needed 21 and Area (m²) 120 → Sheets needed 82. The table below lays out five steps.
QHow are the numbers rounded?
Money is shown to the nearest whole unit, percentages to one decimal place and everything else to two. What you see is rounded; the calculation itself carries the unrounded value forward.
QAnything to watch out for?
XPS and EPS insulation come in slightly different standard sizes — check the product spec before ordering.
Related calculators
Keep your length units consistent across inputs — mixing centimetres and metres throws results far off.