R-values provide a means for quantifying the thermal resistance of an insulating material. If the R-value is high, the material is a good thermal insulator, and heat will not easily flow through it. If the R-value is low, the material is a poor insulator. RSI stands for R-Value Système Internationale, and it also measures thermal resistance but does so using the metric system. Converting one to the other requires some simple math.
Multiply the RSI by 6 to calculate a rough estimate of the R-value. For example, if the RSI is 2, multiply 2 by 6 to get the R-value of 12.
Divide the original RSI value by 0.176. This will calculate the R-value more accurately. For example, if the RSI is 2, calculate 2 / 0.176 to get the R-value of 11.36.
Take the R-value you just found and multiply it by 0.176 to verify that you performed the calculation correctly. This should result in the original RSI value. For example, if you calculated an R-value of 11.36, multiply 11.36 by 0.176 to get the original RSI value of 2.