Note the R-value that you wish to convert. This may be expressed in the form R-19 or simply as a number. Check that it is given in square feet-degrees F-hour per Btu.
Divide the R-value into 1 and note the result. For example, if the R-value is 19, the result is 0.0526.
Check your calculation. Record the result, which is the R-value converted to the U-value in Btu per square foot-degrees F-hour.
Note the R-value that you wish to convert. This may be expressed in the form R-19 or simply as a number. Check that it is given in square feet-degrees F-hour per Btu.
Multiply the R-value by 0.1762 and note the result. For example, if the R-value is 19, the result is 3.348.
Check your work. Record the result, which is the R-value converted to square meters-degrees Celsius per watt.