How many rolls of loft insulation do I need? A table by loft size
A 4 × 6 m loft floor (13.1 × 19.7 ft) is 24 m² and needs 25.2 m² of insulation for one new layer of 170 mm mineral wool with 5% extra: 4 rolls or packs of 8.01 m² each (32.04 m²). The depth, the allowance and the pack coverage are generic example figures, not a product’s and not an insulation design: use the depth and coverage printed on the roll you choose.
| Loft floor | In feet | Loft floor area | With 5% extra | Rolls or packs to buy | Left over | Your loft floor |
|---|---|---|---|---|---|---|
| 3 × 4 m | 9.8 × 13.1 ft | 12 m² | 12.6 m² | 2 rolls or packs of 8.01 m² each (16.02 m²) | 3.42 m² | Open 3 × 4 m in the planner |
| 3 × 5 m | 9.8 × 16.4 ft | 15 m² | 15.75 m² | 2 rolls or packs of 8.01 m² each (16.02 m²) | 0.27 m² | Open 3 × 5 m in the planner |
| 4 × 5 m | 13.1 × 16.4 ft | 20 m² | 21 m² | 3 rolls or packs of 8.01 m² each (24.03 m²) | 3.03 m² | Open 4 × 5 m in the planner |
| 4 × 6 m | 13.1 × 19.7 ft | 24 m² | 25.2 m² | 4 rolls or packs of 8.01 m² each (32.04 m²) | 6.84 m² | Open 4 × 6 m in the planner |
| 4 × 7 m | 13.1 × 23.0 ft | 28 m² | 29.4 m² | 4 rolls or packs of 8.01 m² each (32.04 m²) | 2.64 m² | Open 4 × 7 m in the planner |
| 5 × 6 m | 16.4 × 19.7 ft | 30 m² | 31.5 m² | 4 rolls or packs of 8.01 m² each (32.04 m²) | 0.54 m² | Open 5 × 6 m in the planner |
| 5 × 7 m | 16.4 × 23.0 ft | 35 m² | 36.75 m² | 5 rolls or packs of 8.01 m² each (40.05 m²) | 3.3 m² | Open 5 × 7 m in the planner |
| 5 × 8 m | 16.4 × 26.2 ft | 40 m² | 42 m² | 6 rolls or packs of 8.01 m² each (48.06 m²) | 6.06 m² | Open 5 × 8 m in the planner |
| 5 × 9 m | 16.4 × 29.5 ft | 45 m² | 47.25 m² | 6 rolls or packs of 8.01 m² each (48.06 m²) | 0.81 m² | Open 5 × 9 m in the planner |
| 5 × 10 m | 16.4 × 32.8 ft | 50 m² | 52.5 m² | 7 rolls or packs of 8.01 m² each (56.07 m²) | 3.57 m² | Open 5 × 10 m in the planner |
Each row is the planner’s answer for that loft floor, worked out when this page was built. The link at the end of a row opens the planner with that loft floor filled in, to change the measurements and the product figures.
The table counts rolls for one new layer. It is a quantity, not a design for insulation depth, ventilation, electrics or safe access. A loft that needs more than one new layer takes the floor area times the layers: the loft insulation calculator takes the depths you enter, and How much loft insulation do I need? shows the sum.
The square metres in a roll or pack differ from one product to the next, so the count changes with the roll you choose. The area with the allowance does not: divide it by the square metres printed on your roll or pack and round up.
What the table assumes
Each loft floor is a rectangle.
- Doors and windows are not used for a loft floor quantity.
- Loft insulation: 1 new layer of 170 mm mineral-wool roll over one rectangular horizontal cold-loft floor. This is a material quantity, not a thermal or installation design.
- Every quantity is rounded once, at the end, up to whole packs. Working uses unrounded figures.
- Mineral-wool loft insulation rolls use generic example figures, not the figures of any product. Enter the depth and pack coverage from the chosen roll for a closer answer.
How this table was made
It was worked out when this page was built, by the same room planner and formulas as the editable list: each row is one room sent through the planner. The room sizes are round examples. Product coverage, pack and allowance figures are the planner’s labelled generic examples, not figures for a product.
AI tools drafted the page and automated tests compare every cell with the planner. It has not been checked by a tradesperson or anyone outside the build. No price is shown or used.
Before you use it
Measure only the floor area of your own loft that will be insulated. Check the figures against the room, and follow each product's own instructions: they decide coverage, coats and preparation.
Built and checked with AI tools, not yet by a tradesperson or anyone outside the build. Estimates are arithmetic on your measurements and the figures shown with them: follow each product's own instructions.