Insulation calculator for attics, walls, floors and crawl spaces: how many bags of blown-in cellulose or fiberglass, how many rolls or batts, how many board feet of spray foam, and the R-value you end up with. 48 calculators, free, and they work offline.
No sign-in, no account, no signal needed. Built for insulation contractors, energy auditors and weatherization crews, and simple enough for a homeowner doing their own attic.
WHY IT IS DIFFERENT
Nobody buys "some insulation". You buy enough to hit a target R-value, so every quantity follows one visible chain:
Target R-49 → cellulose R-3.5/in → 14.0 inches → 1,000 sq ft → 70 bags
Switch material and the whole chain re-runs. Every calculator remembers what you typed last, and Home offers "Pick up where you left off".
NEW IN THIS VERSION
✓ Whole-house insulation cost - attic, walls and crawl space or basement priced from your square footage
✓ BTU calculator for air conditioner size, CFM for bath fans and range hoods, and duct size
✓ Dew point and condensation check, whole-wall effective R-value, insulation thickness for any R-value
✓ Attic hatch insulation, polyiso R-value, caulk tubes and acoustic panels (RT60)
✓ "Next calculators" under every result, and share a result with a link to the web version
THE ENVELOPE
✓ Wall batts - net of windows and doors, batt width from stud spacing
✓ Attic blown-in - bags off the coverage chart at depth, with cellulose settling
✓ Attic batts and rolls - how many rolls, first layer plus the cross-laid second layer
✓ Cathedral and vaulted ceilings, floor and crawl space batts
✓ Crawl space encapsulation, basement walls, rim and band joists
✓ Dense-pack retrofit, garage and bonus room package
MATERIALS AND BARRIERS
✓ R-value stack - total R and U for the whole assembly
✓ Climate zone lookup - code minimums by IECC zone, assembly and code year
✓ Spray foam board feet - open cell against closed cell, kits or bulk
✓ Rigid foam board, mineral wool, radiant barrier, vapour barrier
✓ Attic ventilation and baffles, duct and pipe insulation, soundproofing
PERFORMANCE AND ENERGY
✓ Air sealing kit, heat loss and BTU per surface
✓ Energy savings and payback, cost per R, existing R estimator
✓ Insulation removal and a tax credit checker
COSTS AND QUOTING
✓ Labour, material cost from your own price book, markup and margin
✓ Customer quotes, PDF export, shopping lists and job cost tracking
BUILT FOR THE JOB
✓ Type what your tape says: 12' 6-1/2"
✓ Safety warnings where they matter: IC-rated fixtures, flue clearances, and a hard stop on knob-and-tube wiring and vermiculite
✓ R-value chart, climate zone table, safety guide and unit converters
✓ Bright theme, with a dark theme one tap away for dim attics
✓ The same calculators on the web at smartinsulationcalculator.com
FREE, AD-FREE OR PRO
All 48 calculators are free forever; ads support the free tier. Remove Ads Forever is a one-time purchase. Pro Contractor (one time, no subscription) adds unlimited saved projects, branded PDF quotes with your logo, CSV price book import and export, saved assembly templates and widgets. Or watch a short ad for 24 hours of Pro features.
R-value recommendations and coverage figures are reference defaults. The manufacturer's coverage chart governs quantities - always verify local code.
Recent changes:
Remove ads with one simple, one-time purchase, offered under your results. The app is now available in Burmese, Hindi, Spanish, Ukrainian and French. Attic ventilation now defaults to the IRC 1/150 ratio. Smoother ad timing and stability fixes.
Show more
Show less
