Type the area to insulate and the board size. The calculator divides area by one board, adds waste, and rounds pieces up. A 120 m² facade at 60×120 cm and 8% is 181 boards. At 15 cm and λ 0.036, R is about 4.17. An 85 m² roof at 50×100 cm and 10% is 188 pieces.
This calculator converts the insulated surface area into a practical number of boards, batts, or rolls. Depending on the available fields, it can also display an extra value such as thermal resistance R. Also useful: wall area, ridge height, heating power.
Area to insulate, Board width (m), Board length (m) and Custom board area (m²). The result shows up here.
The insulation calculator counts boards and optional R. The formula is ceil((area divided by board area) times (1 plus waste)). Board area comes from width times length unless you type a custom area. R = thickness in meters divided by lambda. A 15 cm thickness is 0.15 m in that quotient.
A 120 m² facade at a 0.6 by 1.2 m board and 8% waste is 181 pieces. R at 15 cm and λ 0.036 is about 4.17. An 85 m² wall at 50×100 cm, 10%, 20 cm, and λ 0.039 is 188 pieces and R about 5.13. An attic 42 m² at large 120×270 cm, 5%, 10 cm, and λ 0.031 is 14 pieces and R about 3.23.
Type area to insulate and board width and length in the header unit. Waste, custom area, thickness, lambda, and price are optional. A 60×120 cm board is 0.6 and 1.2 m, not 60 and 120. A comma in 0.6 works like 0,6.
Take 120 m² from wall area or from ridge and pitch on paper. Heating 2000 W from 50 m³ is another formula. Paint does not turn into foam boards.
Eight percent waste on 167 net pieces (120 / 0.72) covers cuts at openings and gives 181. R 4.17 is a sketch from λ, not a certificate. Typing 60 as width in meters instead of 0.6 understates the board count a hundred times.
Type 120, 0.6, and 1.2, set 8%, 150 mm, and 0.036, click Calculate, and match 181 boards and R ≈ 4.17. Then 85, 0.5, and 1.0 at 10%: 188 pieces.
A 120 m² facade at 60×120 cm and 8% is 181 boards. At 15 cm and λ 0.036, R is about 4.17.
You need 181 boards
Thermal resistance R ≈ 4.17
This is a practical example for a large surface, where even a modest waste percentage translates into many extra boards.
You need 188 pieces
Thermal resistance R ≈ 5.13
On roof slopes, extra material is usually needed more often than on flat wall areas because there are more cuts and shape adjustments.
You need 14 pieces
Thermal resistance R ≈ 3.23
On smaller projects, the piece count can be easy to underestimate, so the calculator helps organize purchasing and avoid shortages.
62 boards
How many 60×120 cm boards for 40 m² at 10% waste? 62 boards.
38 boards
Thermal resistance R ≈ 2.78
How many 60×120 cm boards for 25 m² at 8% waste, and what R at 100 mm? 38 boards, R ≈ 2.78.
135 boards
Thermal resistance R ≈ 5.13
How many 50×100 cm boards for 60 m² of roof at 12% waste? 135 boards, R ≈ 5.13.
24 boards
Thermal resistance R ≈ 3.53
How many 60×120 cm boards for a 15 m² dormer at 15% waste? 24 boards, R ≈ 3.53.
117 boards
Thermal resistance R ≈ 2.58
How many 60×120 cm boards for 80 m² of floor at 5% waste? 117 boards, R ≈ 2.58.
181. Board area 0.72 m², 120 / 0.72 ≈ 166.7, times 1.08, rounded up.
About 4.17. 0.15 / 0.036. A sketch from two fields, not an audit.
188 pieces. Board area is 0.50 m², and R at 20 cm and λ 0.039 is about 5.13.
14 pieces. One board is 3.24 m², and R at 10 cm and λ 0.031 is about 3.23.
As 0.6 and 1.2 m, or a custom area of 0.72 m². Typing 60 and 120 would mean 7200 m² per board.
Usually 5-10% for openings and corners. 8% on 120 m² lifts 167 to 181.
From wall area, minus openings. A 5.60 m ridge helps a roof plane, not a vertical wall.
Not in this calculator. Power = m³ × W/m³. R stays a separate sketch.
No. Board count follows area and board size. Lambda and thickness only serve R.
Round up to 181. A fraction of a board is not in the pack.
Volume and waste come from the sizes you type. Below are volume and NIST SI units.
Page updated in 2026.
