Loft Insulation Calculator 2026
Instantly estimate the number of insulation rolls, material volume, and coverage needed for your loft insulation project. Calculate area, thickness, and quantities with precision.
Loft Dimensions & Insulation Specs
Define your loft area and insulation parameters
Total length of the loft space
Most common type for DIY loft insulation
Recommended: 270mm for optimal energy efficiency
Coverage per roll (standard roll: 8.1m × 0.91m = 7.38m²)
Extra material for cuts, gaps, and irregular areas
Material Estimates
Insulation rolls and coverage breakdown
Enter your loft dimensions and insulation specs above, then click Estimate Insulation Materials to reveal your complete material list.
Common Insulation Types & Coverage
Standard insulation roll dimensions and their approximate coverage area. Always add 10% for wastage and cuts.
| Insulation Type | Standard Roll Size | Coverage (m²) | Typical Use |
|---|---|---|---|
| Mineral Wool | 8.1m × 0.91m | 7.38 | Standard lofts |
| Fibreglass Roll | 7.5m × 1.2m | 9.00 | Wide joist spacing |
| Rigid Foam Board | 1.2m × 2.4m | 2.88 | Limited space |
| Sheep’s Wool | 6.0m × 0.9m | 5.40 | Eco-friendly builds |
| Blown Fibre | Per m² coverage | 1.00 | Hard-to-reach areas |
Loft Insulation FAQ
Learn more about loft insulation requirements, installation tips, and material calculations for your home improvement project.
The amount of loft insulation needed depends on your loft area and desired thickness. Current building regulations recommend 270mm (10.6 inches) of mineral wool insulation for optimal energy efficiency. Measure your loft length and width to calculate the total area, then determine how many rolls you need based on the coverage per roll.
Current UK building regulations recommend a minimum of 270mm (10.6 inches) of mineral wool insulation for lofts. This typically involves laying 100mm between the joists and 170mm cross-laid on top. For older homes, upgrading to 300mm can provide additional energy savings and improved thermal performance.
First, calculate your loft area by multiplying length by width. Then check the coverage area of one roll (typically 7.38m² for standard 8.1m × 0.91m rolls). Divide your total loft area by the coverage per roll, then add 10% for wastage and cuts. For example, a 40m² loft needs approximately 6 rolls (40 ÷ 7.38 = 5.4, rounded up to 6).
Mineral wool (glass wool or rock wool) is the most common and cost-effective loft insulation. It’s easy to install, fire-resistant, and provides excellent thermal performance. Alternatives include rigid foam boards (better for limited space), sheep’s wool (eco-friendly), or blown fibre insulation (ideal for hard-to-reach areas).
Yes, loft insulation is one of the most straightforward DIY home improvement projects. You’ll need protective clothing (mask, gloves, goggles), a loft ladder, and proper lighting. Ensure adequate ventilation, avoid compressing the insulation (which reduces effectiveness), and never block eaves ventilation. For complex lofts or if you’re unsure, consider professional installation.