Estimate insulation for walls, ceilings, floors, rooms, and known areas using manufacturer coverage, product dimensions, or loose-fill yield. Subtract selected openings, add one waste allowance, and optionally estimate nominal R-value thickness and material cost.
The calculator finds gross surface area, subtracts only the openings you enter, and applies the selected extra allowance once.
Area-based products divide recommended area by manufacturer coverage or calculated unit coverage. Loose fill uses either manufacturer area coverage per bag or volume yield per bag—never an assumed universal density.
length × height (or width) × quantity2 × (length + width) × wall heightlength × width(gross area − deductions) × (1 + extra %)ceiling(recommended area ÷ coverage per purchase unit)recommended area × installed depthtarget R-value ÷ product R-value per inchA 20 × 8 ft wall is 160 ft². Subtract a 12 ft² window and add 10% for 162.8 ft². At 40 ft² per package, exact need is 4.07; buy 5 packages, covering 200 ft² with 37.2 ft² estimated leftover.
A 12 × 10 ft room with 8 ft walls has 352 ft² of walls and a 120 ft² ceiling. Selecting both gives 472 ft²; 10% extra gives 519.2 ft², or 7 rolls at 80 ft² each.
For 500 ft² plus 10% extra, 4 × 8 ft rigid boards cover 32 ft² each. Exact need is 17.1875, so buy 18 boards per required layer.
For 25 m² plus 10% extra, 1.2 × 2.4 m boards cover 2.88 m². Exact need is about 9.55, so buy 10 boards per layer.
Package coverage and loose-fill yield vary by manufacturer, product, installed depth, and target R-value.
Small openings may not reduce purchase needs because cutoffs can be reused; the calculator subtracts only entries you add.
Framing fit, compression, settling, thermal bridging, air sealing, and local requirements can affect the finished assembly.
Prefer manufacturer package coverage when available. Dimension mode multiplies batt or roll dimensions by pieces per package; rigid board mode uses board face area. Rigid-board layers are optional nominal arithmetic.
Choose area coverage when the label states how much area one bag covers at the selected depth or R-value. Choose volume yield only when the manufacturer provides volume per bag; installed depth then determines required volume.
Extra insulation is applied once after deductions. Purchase quantities round upward, and leftover is purchased coverage minus recommended coverage.
R-value describes resistance to heat flow. Target divided by R per inch gives theoretical material thickness. This does not model framing thermal bridges, air films, sheathing, installation quality, an entire assembly, climate requirements, or code compliance.
Optional cost multiplies purchase units by entered price. It excludes labor, vapor control, air sealing, fasteners, finishes, removal, delivery, taxes, and permits.
Calculate net surface area, add an appropriate extra allowance, and divide by verified product coverage.
Multiply wall length by height and quantity, then subtract only measured openings you choose to deduct.
Divide recommended area by manufacturer package coverage, or calculate coverage from piece dimensions and pieces per package.
Divide recommended area by board face area, round upward, and multiply by nominal layers only if that option is used.
Only if appropriate for your estimating method. The calculator never subtracts them automatically.
The editable presets are planning aids; cuts, reuse, damage, and product format determine a suitable allowance.
Use known area or loose-fill mode and the manufacturer coverage or yield for the selected installed depth and R-value.
Use manufacturer area coverage per bag or volume yield per bag. There is no universal bags-per-volume conversion.
It is a measure of resistance to heat flow; higher material R-values indicate greater resistance under rated conditions.
No. It does not infer climate zones, assembly performance, or code compliance.
No. Optional pricing is a material-only purchase-unit estimate.