🌡️

R-Value Calculator

Drywall (0.45/layer)

Insulation R per inch

Insulation Thickness (in)

Sheathing (0.6/layer)

Insulation Type

Climate Zone

Waste Factor

Result

—total R-value

◆ LIVE 3D PREVIEW

U-Value

—

Code Minimum

—

How to Calculate R Value

Use this free r value calculator to get instant, accurate results for your construction project. Simply enter your measurements above and the calculator will automatically compute the result using industry-standard formulas.

Pro Tip: Always add 10-15% extra material to account for waste, cuts, and job-site conditions. This is standard practice recommended by experienced contractors.

Related Calculators

▸ Home Value After Renovation ▸ Insulation R Value ▸ 2x4 ▸ 3 4 5 Rule ▸ Ac Size ▸ Ac Tonnage

💡 Pro Tips — R Value

R-value targets: Attic R-49 to R-60, walls R-13 to R-21, floor R-25 to R-30.
Don't compress batts — squished insulation loses R-value. It needs full loft to work.
Vapor barrier goes on warm side — interior side in cold climates, exterior in hot.
Spray foam also air-seals — worth the premium in drafty old homes.
Blown-in is best for attics — fills all gaps and irregularities that batts miss.

📊 R-Value by Climate Zone

Zone	Attic	Walls	Floor
1-2	R-30 to R-49	R-13	R-13
3-4	R-38 to R-60	R-13 to R-21	R-19
5-6	R-49 to R-60	R-20+	R-25 to R-30

❓ Frequently Asked Questions

+What R-value do I need?

Depends on climate zone. Attics: R-30 to R-60. Walls: R-13 to R-21. Floors: R-13 to R-30. Check your local energy code.

+Which insulation type is best?

Batts: cheapest, DIY-friendly. Blown-in: best for attics. Spray foam: best air sealing + highest R per inch. Each has its place.

+Does old insulation need removal?

Usually no — you can add new insulation on top. Exception: if it is wet, moldy, or contains vermiculite (potential asbestos source).

+Where does air really leak?

Top air leak spots: attic hatches, recessed lights, plumbing/duct penetrations, electrical outlets on exterior walls, and rim joists.