From measured space to purchasable material
Loose-fill insulation products can state minimum bags per area as well as an installed depth requirement. This calculator offers a product coverage-chart method and a separate volume-and-density budget. Use the chart when the selected product specifies bag coverage for the target performance. The volume method shows the arithmetic of added depth and mass but does not establish an R-value. Existing insulation, settling, obstructions, ventilation baffles, and installation density affect the actual work. Keep these conditions in the project specification instead of assuming a depth measurement alone proves the installation is complete.
Measure, select yield and round the order
- Select the actual product and target installation rating.
- Use its coverage chart when minimum bags are specified.
- Enter added depth and compare the whole-bag estimate with the installation specification.
Net requirement and purchase calculation
A worked example
1000 ÷ 30 × 1.05 = 35 bags in chart mode. At $18 each, the entered material budget totals $630.
Blown-In Insulation Bag: what changes the result?
Check product dimensions before treating area as a shopping quantity. The comparisons below are calculated from this page’s default example. Each row changes only the named input; all other inputs stay at their displayed example values. These are mathematical scenarios, not measurements from a completed project.
| Changed assumption | Default input | Comparison input | Result: default → comparison |
|---|---|---|---|
| Installation area | 1,000 sq ft | 1,200 sq ft | Loose-fill bags: 35 → 42 Added settled volume: 833.3333 → 1,000 cu ft |
| Added settled depth | 10 in | 12 in | Added settled volume: 833.3333 → 1,000 cu ft |
| Bag mass | 25 lb | 30 lb | Purchased bag mass: 875 → 1,050 lb |
| Coverage per bag at target rating | 30 sq ft | 36 sq ft | Loose-fill bags: 35 → 30 Purchased bag mass: 875 → 750 lb |
Displayed values are rounded. Whole-pack results change in steps; continuous quantities may change before a new pack is needed. To compare your actual project, enter your dimensions above, save a scenario, then change one assumption.
Coverage, allowance and purchasing limits
- The density default is illustrative and must be replaced with the selected product value.
- Adding depths of different materials does not directly establish total thermal performance.
- A purchase allowance cannot excuse installing less than the specified bag mass.
Frequently asked questions
How many bags for a 1000 sq ft attic?
At 30 sq ft per bag from the selected chart and 5% extra, the example needs 35 bags.
Does this calculator give an R-value?
No. Use the tested product coverage, depth, and minimum bag requirements for the target rating.
Can I account for existing insulation?
Enter the added depth from the installation plan and follow product guidance for installation over existing material.
Read the project guides
- Insulation Quantity Planning: Batts, Rolls, and Blown-In Bag Budgets
Choose a quantity model that matches insulation packaging: cavity-sized batts, full-length roll strips, or product-chart loose-fill bags.
Calculation method: JICWH methodology. Examples are planning assumptions, not product recommendations.