What this converter does
This converter turns metric RSI (m²·K/W) into US R-value and back. One RSI equals about 5.678 R — so an RSI-3.5 batt is roughly R-20. Type a value, pick your units, and read the result instantly.
RSI and R-value both measure resistance to heat flow: higher means better insulation. For the reverse rate of heat flow, 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 RSI-3.5 wall batt to R-value.
1 RSI = 5.678 R3.5 × 5.678 = 19.9 RAn RSI-3.5 batt is about R-20 in US terms.
The units in this example
The metric measure of thermal resistance used on insulation sold 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
The US measure of thermal resistance, printed on 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