Calculator Inputs and Outputs
Inputs
- Layer 1 R-value — example: 13
- Layer 2 R-value — example: 19
- Layer 3 R-value — example: 5
- Interior air film R-value — example: 0.68
- Exterior air film R-value — example: 0.17
Results
- Total R-value
- Approx. U-factor
Formula used
Series thermal resistances add; U-factor is approximately 1 ÷ total R-value.
How to Use the Insulation R-Value Calculator
Enter the requested values, confirm the units and assumptions, then select Calculate Insulation R-Value. The default inputs provide a working example, and the supporting outputs make the result easier to check.
Formula
Series thermal resistances add; U-factor is approximately 1 ÷ total R-value.
Understanding the Results
The primary answer appears first, followed by related values, conversions, or comparisons. Calculations retain additional internal precision before the displayed result is rounded.
Accuracy Tips
- Use consistent units and measured values.
- Review whether the formula assumptions match your situation.
- For estimates, include realistic waste, efficiency, fees, or contingency values where available.
Important Note
This calculator is for informational estimation. Verify critical financial, health, construction, scientific, tax, legal, or safety decisions with an appropriately qualified professional.
Calculation Standards
This tool uses documented formulas and high-precision internal values. Displayed results may be rounded for readability. Review the assumptions and verify important decisions with a qualified professional.
Read our calculation methodology