How to Convert Between U-Factor and R-Factor

The U/R-Factor Converter calculates the equivalent thermal resistance or transmittance using the following conversion formula:

From U-Factor to R-Factor:

From R-Factor to U-Factor:

Where:

• \( U\text{-Factor} \): Thermal transmittance, measured in BTU/h·°F·ft², represents the rate of heat transfer.
• \( R\text{-Factor} \): Thermal resistance, measured in h·°F·ft²/BTU, indicates the ability to resist heat flow.

Select the input unit (U-Factor or R-Factor), enter the value, and the calculator will compute the corresponding value in the other unit.

Using the U/R-Factor Converter

This converter assists architects, engineers, and builders in converting between U-Factor and R-Factor for insulation and building material assessments.

Choose the input unit (U-Factor or R-Factor), enter the value, and click "Convert." The calculator will display both U-Factor and R-Factor, rounded to 6 decimal places.

Example: Convert a U-Factor of 0.1 to R-Factor.

1. Input Value: \( 0.1 \, \text{BTU/h·°F·ft²} \)
2. Unit: \( U\text{-Factor} \)
3. Conversion: \( R\text{-Factor} = 1 / 0.1 = 10 \, \text{h·°F·ft²/BTU} \)
4. Result: \( 0.1 \, U\text{-Factor} = 10 \, R\text{-Factor} \)

Example: Convert an R-Factor of 5 to U-Factor.

1. Input Value: \( 5 \, \text{h·°F·ft²/BTU} \)
2. Unit: \( R\text{-Factor} \)
3. Conversion: \( U\text{-Factor} = 1 / 5 = 0.2 \, \text{BTU/h·°F·ft²} \)
4. Result: \( 5 \, R\text{-Factor} = 0.2 \, U\text{-Factor} \)

Use this tool for thermal performance calculations in construction.

Common Conversion Table

The following table provides quick reference conversions for common U-Factors and R-Factors:

U-Factor (BTU/h·°F·ft²)	R-Factor (h·°F·ft²/BTU)
0.1	10.000
0.2	5.000
0.5	2.000
1.0	1.000
10.0	0.100

Use the calculator for precise conversions of any U-Factor or R-Factor.

Common FAQ

Below are frequently asked questions about U-Factor and R-Factor conversions:

• Q: What is the relationship between U-Factor and R-Factor?
  A: R-Factor is the inverse of U-Factor, with \( R = 1 / U \) and \( U = 1 / R \), both measuring thermal performance in different units.
• Q: Why choose between U-Factor and R-Factor?
  A: U-Factor is common in Europe, while R-Factor is standard in the U.S., allowing conversion for international building standards.
• Q: How accurate is this converter?
  A: The converter uses the exact formula \( R = 1 / U \) or \( U = 1 / R \) and provides results rounded to 6 decimal places.
• Q: Can zero or negative values be converted?
  A: No, values must be positive and non-zero, as division by zero is undefined, and negative values are not physically meaningful.
• Q: Where is this used?
  A: This is used in building insulation design, energy efficiency ratings, and material selection.