- No data uploaded
- Instant results
Insulation R-Value Calculator
Find the recommended attic R-value for your IECC climate zone and how many inches of batts, blown cellulose or spray foam to add.
Insulation R-Value Calculator
Target attic R-valueAdd R-51 = 15.9 in of this material
Existing (est.)
R-9
Volume to add
1,594 ft³
IECC 2021 ceiling/attic recommendations: R-30 (zone 1), R-49 (zones 2–3), R-60 (zones 4–8). Seal air leaks before adding insulation.
Planning estimates only. Building codes, loads and material specs vary — have a licensed engineer or contractor confirm quantities and safety requirements. Disclaimer
Important
Quantity estimates for planning and ordering. Structural members, reinforcement and footings must be designed by a qualified engineer to local code.
Frequently asked questions
Is my data uploaded?
No. The calculation runs entirely in your browser — nothing you type is sent to a server.
Is it free?
Yes — free, unlimited and no sign-up.