Insulation Calculator
Bags or batts to reach your target R-value.
Your estimate
Estimates only. Renovate Cafe's calculators are a planning aid, not professional advice — double-check your inputs, confirm coverage on the product you buy, and verify quantities and local code for structural, electrical, or permitted work. Disclaimer.
Enter the area, where it's going, and the R-value you're aiming for. Renovate Cafe returns the bags of batts or blown-in insulation that covers it, plus the cost — and a quick read on whether your target fits the space.
Match the R-value to the space
Insulation is rated by R-value — its resistance to heat flow. More is better, up to a point, and the right target depends on where it goes and your climate. Walls are limited by stud depth (about R-13 to R-15 in a 2×4 wall, R-19 to R-21 in a 2×6). Attics have room to go thick, and modern cold-climate recommendations run R-38 to R-49.
The calculator takes your area and the R-value you choose and looks up how much one bag covers at that rating. Batts come bundled by how many square feet they cover at a given R-value; blown-in fiberglass covers fewer square feet per bag the higher you go, because you're piling it deeper. Either way, you get the bag count and the cost.
Batts or blown-in?
Batts are simple and cheap for open stud and joist bays you can reach — walls during a remodel, an accessible floor. Blown-in shines in attics, where you can cover an irregular floor evenly and bury obstructions, and it's the faster way to top up an attic that's under-insulated. Many rental machines come free with a bag purchase.
Whatever you choose, don't compress it — insulation works by trapping air, and a batt jammed into too small a cavity loses much of its rated value. Air-seal gaps and penetrations first; insulation slows heat, but it won't stop a draft.
Frequently asked questions
What R-value do I need for my attic?
How many bags of insulation do I need?
Should I use batts or blown-in insulation?
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