What this converter does
This converter turns US R-value into metric RSI (m²·K/W) and back. Multiply R by 0.1761 to get RSI — so an R-20 batt is about RSI-3.5. Type a value and read the result as you type.
Both rate resistance to heat flow, where higher is better insulation. For the heat-flow rate itself, see the U-value converter.
The units it covers
These measure thermal resistance, converting through the metric RSI (m²·K/W) with a fixed ratio.
View all units & their values
| Unit | Symbol | Value | Mainly used |
|---|---|---|---|
| RSI (m²·K/W) | RSI | 1 | Metric insulation rating |
| R-value (ft²·°F·h/BTU) | R | 0.1761 | US insulation rating |
| Clo | clo | 0.155 | Clothing insulation |
The formula
Each unit has a fixed value in RSI, so converting between any two means going through it once:
result = value × factor_from ÷ factor_toWhere:
- value = the number you typed
- factor_from = the “from” unit’s value in RSI
- factor_to = the “to” unit’s value in RSI
Worked example
Convert an R-30 attic insulation to RSI.
1 R = 0.1761 RSI30 × 0.1761 = 5.28 RSIAn R-30 attic batt is about RSI-5.3.
The units in this example
The US measure of thermal resistance printed on insulation batts and boards. Higher R means more resistance to heat flow.
- 1 R = 0.1761 RSI
- R-13 ≈ RSI 2.3
- R-20 ≈ RSI 3.5
- R-30 ≈ RSI 5.3
The metric measure of thermal resistance used on insulation outside the US. Higher RSI means better insulation.
- 1 RSI = 5.678 R
- RSI 2.0 ≈ R-11
- RSI 3.5 ≈ R-20
- RSI 7.0 ≈ R-40