R-value per Inch Table
R-value per Inch Table
Compare typical R-value per inch ranges for insulation materials and link the values to thickness calculators.
Reference
R-value per inch table for insulation materials
This R-value per inch table is a quick reference for common insulation and building materials. Values are typical ranges, not certified declarations. Use the range to estimate starting thickness, then confirm the selected product label, density, installation method, temperature behavior, and local requirements. The table is most useful when moving from a target R-value to an approximate insulation depth.
Typical values are educational planning references. Always check local code, product documentation, and project-specific constraints.
Typical R-value per inch table
Ranges are planning references. Use product declarations for purchase, compliance, and final design.
| Material | Typical R/in | Metric equivalent | Common use | Notes | Calculator link |
|---|---|---|---|---|---|
| Fiberglass batt | R-3.0 to R-3.8 | 0.53 to 0.67 m²K/W per 25.4 mm | wall and ceiling cavities | compression reduces performance | Thickness |
| Blown fiberglass | R-2.2 to R-3.7 | 0.39 to 0.65 m²K/W per 25.4 mm | attics and voids | depends on blown density | Attic |
| Cellulose | R-3.2 to R-3.8 | 0.56 to 0.67 m²K/W per 25.4 mm | attics and walls | check settling and moisture | Attic |
| Mineral wool | R-3.7 to R-4.3 | 0.65 to 0.76 m²K/W per 25.4 mm | walls, roofs, acoustics | density changes value | Mineral wool |
| EPS | R-3.6 to R-4.2 | 0.63 to 0.74 m²K/W per 25.4 mm | continuous boards | board grade matters | EPS |
| XPS | R-4.5 to R-5.0 | 0.79 to 0.88 m²K/W per 25.4 mm | foundations and boards | check long-term value | XPS |
| Polyiso | R-5.0 to R-6.5 | 0.88 to 1.14 m²K/W per 25.4 mm | roofs and continuous insulation | temperature can change result | Thickness |
| Open-cell spray foam | R-3.5 to R-3.8 | 0.62 to 0.67 m²K/W per 25.4 mm | cavities and air sealing | needs moisture review | Required R |
| Closed-cell spray foam | R-6.0 to R-7.0 | 1.06 to 1.23 m²K/W per 25.4 mm | thin assemblies | check declaration and thickness | Required R |
| Wood | R-1.0 to R-1.4 | 0.18 to 0.25 m²K/W per 25.4 mm | structure and lining | not primary insulation | Materials |
| Brick | R-0.1 to R-0.3 | 0.02 to 0.05 m²K/W per 25.4 mm | masonry and mass | moisture and density matter | Brick |
| Concrete | R-0.08 to R-0.2 | 0.01 to 0.04 m²K/W per 25.4 mm | structure | high mass, low insulation | Concrete |
| Air space | orientation-dependent | condition-dependent | cavities | only under controlled conditions | Layers |
R-value per inch table for insulation materials
Example: R-38 divided by R-3.8 per inch gives about 10 inches before installation allowances.
Typical values are educational planning references. Always check local code, product documentation, and project-specific constraints.
Practical note
How to interpret the calculator result
R-value per inch table for insulation materials is intended for quick option checks and technical discussion before detailed execution. The result depends on the selected units, declared material values, and chosen surface resistances, so each change in layer or thickness should be treated as a separate variant.
The calculator does not automatically verify every local rule, thermal bridge, moisture condition, structural connection, or installation tolerance. If the result is close to a requirement, treat it as a reason for deeper verification rather than a final decision.
For better comparisons, test several realistic thicknesses, check current product data sheets, and review the complete assembly. A calculated value is most useful when the assumptions are clear: material, thickness, layer order, units, and data source.
For insulation or U-value tools, layer order and correct units are especially important. For concrete, electrical, plumbing, or heating tools, the result should be read as a quick quantity or plausibility check before standards and execution conditions are reviewed.
Save the result with the date, material name, and assumptions. If the product, diameter, cable section, or thickness changes later, do not compare the numbers alone without checking which inputs changed.
For calculator pages, clear separation between inputs and result is essential. If a value looks surprising, check units and default fields first, then review the project assumptions.
Assembly thickness
Assembly thickness
Use the tables and formulas to choose a sensible starting thickness before checking the exact assembly.
U-value
U-value
Keep R-value, U-factor, U-value, lambda, k-value, and unit systems separate before comparing results.
CategoryLambdaLayerMaterialThickness
How it works
Use with care
Ranges vary by density, facing, blowing depth, aging method, moisture, and manufacturer.
Next step
Open the insulation thickness calculator after choosing a realistic R per inch.
R-value per Inch Table
Thickness in inches = target R-value / selected R-value per inch.
This R-value per inch table is a quick reference for common insulation and building materials. Values are typical ranges, not certified declarations. Use the range to estimate starting thickness, then confirm the selected product label, density, installation method, temperature behavior, and local requirements. The table is most useful when moving from a target R-value to an approximate insulation depth. Example: R-38 divided by R-3.8 per inch gives about 10 inches before installation allowances.
Add layerRestore default setupRemove
Assembly nameThickness unitInternal Rsi (m2K/W)External Rse (m2K/W)
Calculation assumptions
The calculators use visible formulas and explicit unit conversions. Treat the result as a preliminary check, not a complete building design.
- SI and US units are converted separately; R, RSI, U-value, and U-factor are not mixed without the unit factor.
- Enter positive values and compare the result with the selected product datasheet.
- Local codes, thermal bridges, fasteners, and installation quality can change the requirement.
- Last formula review: 2026-04-27.
See how formulas, unit conversions, rounding, and limitations are handled. Methodology details.
US R-value mini-hub
Move between R-value calculators, material tables, insulation comparisons, and assembly calculators without scanning the whole navigation.
R-value calculators
Material R-values
Insulation comparisons
Assembly calculators
Reference tables
Reference FAQ
No. They are educational references for planning, comparison, and calculator input checks.
Use typical values only for early estimates. Product labels, declarations, and local rules should override them.
R-value and U-factor are common in US practice, while lambda and U-value are common in SI reporting. The pages keep unit systems explicit.
Yes. You can print the result or export it to CSV, Excel, or PDF for reports and documentation.
Yes. It is designed for layered assemblies such as external walls, flat roofs, pitched roofs, floors, and slabs. For unusual assemblies, add every relevant layer and treat the result as a planning check before formal verification.
Yes. It is intended for fast concept-stage calculations, insulation comparison, and envelope optimisation before detailed design. It is best used to narrow choices, not to replace a code check or project-specific thermal bridge assessment.
Yes. You can switch between millimeters, centimeters, and inches, and the calculator keeps the values consistent. For fewer mistakes, choose one unit system at the start of a project and review converted thicknesses before export.
Use R-value per inch table for insulation materials as a first-pass reference. Before specifying anything, compare the result with the local requirement, actual project dimensions, product data sheet, and local requirements.