R-Value Calculator
Use the R-Value Calculator to measure R-values and U-values of materials based on your inputs for thermal conductivity, thickness, and type.
Calculate R-value in seconds
Add multiple materials for layered designs
Use metric or imperial units
Download a professional PDF report with your results
| Total Values | |
|---|---|
| Name: | |
| Total R-Value: | -- ft²·°F·hr/BTU |
| Total U-Value: | -- BTU/(hr⋅ft²⋅°F) |
What Is R-Value & Why Does It Matter?
R-Value measures how well a material resists heat transfer, which is essential for choosing effective insulation. Engineers and architects rely on it to design buildings that meet energy standards and maintain comfortable temperatures year-round.
When you calculate R-values, you can find the right mix of materials to reduce heat loss and cut energy costs. This is especially important in HVAC design, where insulation performance directly affects heating and cooling efficiency.
Accurate R-value calculations also help you stay compliant with building codes and support sustainability goals. Ultimately, getting insulation right means your projects are more comfortable, efficient, and environmentally responsible.
R-Value Variables
Material Type
The type of material significantly impacts its thermal resistance, as different materials conduct heat at varying rates.
Material Thickness
The thickness of a material directly affects its R-value, with thicker layers generally providing better thermal resistance.
Thermal Conductivity
Thermal conductivity measures how easily heat passes through a material, with lower values indicating better insulation properties.
No. Of Layers
Many designs include multiple material layers, like insulation, drywall, and exterior cladding, each contributing to the total R-value.
R-Value Formula
The R-value is calculated using the following equations in both imperial and metric:
Imperial Equation
Following the formula below, you can calculate the R-value:
Components:
R = Thermal resistance (ft²·°F·hr/BTU)
d = Material thickness (inches, in)
k = Thermal conductivity of the material (BTU·in/hr·ft²·°F)
In the imperial system, the R-value is calculated by dividing the material's thickness (in inches) by its thermal conductivity (in BTU·in/hr·ft²·°F). Higher values indicate superior insulation properties.
Metric Equation
Following the formula below, you can calculate the R-value:
Components:
R = Thermal resistance (m²·K/W)
d = Material thickness (meters, m)
λ (Lambda) = Thermal conductivity of the material (W/m·K)
In the metric system, the R-value is determined by dividing the material's thickness (in meters) by its thermal conductivity (in watts per meter per Kelvin). A higher R-value indicates better insulation performance.
R-Value Calculations In h2x
h2x makes insulation and R-value calculations faster and more reliable.
See why thousands of engineers trust h2x for their design workflows:
Smart Layouts: Draw and adjust systems quickly with auto-connected components.
Verified Sizing: Create accurate, CIBSE-verified calculations that update instantly.
Easy Exports: Download branded PDFs or AutoCAD and Revit files in one click.
Detailed Reports: Get calculation summaries and bills of materials for easy reviews.
