Convert R-value (US, ft²·°F·h/BTU) (R (US)) to RSI (m²·K/W) (RSI)
A Canadian insulation label says RSI 5.3, the US one says R-30 — same product. US R-values are 5.678× the metric RSI, and mixing them up means a badly under- or over-specified wall.
Formula
1 R (US) = 0.17611 RSI
To convert R (US) to RSI, divide the value by 5.678263.
Conversion Table
| R-value (US, ft²·°F·h/BTU) (R (US)) | RSI (m²·K/W) (RSI) |
|---|---|
| 1 R (US) | 0.1761 RSI |
| 2 R (US) | 0.3522 RSI |
| 3 R (US) | 0.5283 RSI |
| 5 R (US) | 0.8806 RSI |
| 8 R (US) | 1.4089 RSI |
| 10 R (US) | 1.7611 RSI |
| 11 R (US) | 1.9372 RSI |
| 13 R (US) | 2.2894 RSI |
| 15 R (US) | 2.6417 RSI |
| 19 R (US) | 3.3461 RSI |
| 21 R (US) | 3.6983 RSI |
| 25 R (US) | 4.4028 RSI |
| 30 R (US) | 5.2833 RSI |
| 38 R (US) | 6.6922 RSI |
| 40 R (US) | 7.0444 RSI |
| 49 R (US) | 8.6294 RSI |
| 60 R (US) | 10.5666 RSI |
Common R (US) to RSI Examples
- 3 R (US) = 0.5283 RSI
- 10 R (US) = 1.7611 RSI
- 13 R (US) = 2.2894 RSI
- 19 R (US) = 3.3461 RSI
- 21 R (US) = 3.6983 RSI
- 30 R (US) = 5.2833 RSI
- 38 R (US) = 6.6922 RSI
- 49 R (US) = 8.6294 RSI
About R (US) to RSI
The factor comes from converting ft²·°F·h/BTU to m²·K/W: R (US) = RSI × 5.678. Typical targets translate like this: an R-13 stud wall is RSI 2.3, R-30 attic insulation is RSI 5.3, and the R-49 recommended for cold-climate attics is RSI 8.6.
Watch which label a foreign product uses: European mineral wool sold with "R = 5" usually means RSI 5 — i.e. R-28 in US terms, not a thin R-5 batt. When a datasheet seems 5–6× off, this unit mix-up is almost always why.
About the units
R-value (US, ft²·°F·h/BTU) (R (US)) — The US R-value rates insulation in ft²·°F·h/BTU — the number on every American insulation batt (R-13 walls, R-30 to R-49 attics). Higher is better.
RSI (m²·K/W) (RSI) — RSI is the metric insulation rating in m²·K/W used in Canada, Europe and Australia. One RSI equals about R-5.68 in US terms, so metric and US product labels differ by that factor.
Frequently Asked Questions
What is R-30 in metric RSI?
RSI 5.28 — divide the US R-value by 5.678.
Why do the US and Canada use different insulation numbers?
Same physics, different units: the US rates in ft²·°F·h/BTU, Canada and Europe in m²·K/W (RSI). The US number is always the bigger one, by a factor of 5.678.
How do R (US) and RSI compare in size?
Compare them through the ratio: 1 R (US) equals 0.17611 RSI, which shows directly which unit represents a larger amount of Insulation R-value.
What should I check before trusting a R (US) to RSI result?
Confirm the input value, the unit direction (R (US) to RSI, not the reverse), and that the formula 1 R (US) = 0.17611 RSI has been applied.
Can I convert large numbers of R (US) to RSI at once?
Yes. The same ratio 0.17611 applies to any value, whether it is a fraction or millions of R (US).
Is there a shortcut for converting R (US) to RSI?
The shortest route is the formula itself: 1 R (US) = 0.17611 RSI. Memorizing this single line covers every case.
Where does the unit R (US) come from?
The US R-value rates insulation in ft²·°F·h/BTU — the number on every American insulation batt (R-13 walls, R-30 to R-49 attics). Higher is better.
Where does the unit RSI come from?
RSI is the metric insulation rating in m²·K/W used in Canada, Europe and Australia. One RSI equals about R-5.68 in US terms, so metric and US product labels differ by that factor.