Pressure
Convert inch of water column (inH₂O) to pound per square inch (psi). Pressure is force per unit area. Process engineers move constantly between SI (kPa, bar) and US (psi) units, and between absolute and gauge.
1 inH₂O = 0.03612729 psi
To convert inch of water column to pound per square inch, multiply the inH₂O value by 0.03612729. To go the other way, divide by 0.03612729 (or multiply by 27.6799).
| inH₂O | psi |
|---|---|
| 1 | 0.03612729 |
| 2 | 0.07225458 |
| 5 | 0.1806365 |
| 10 | 0.3612729 |
| 25 | 0.9031823 |
| 50 | 1.806365 |
| 100 | 3.612729 |
| 250 | 9.031823 |
| 500 | 18.06365 |
| 1000 | 36.12729 |
Line and vessel ratings, pump discharge heads, and relief set points are all specified in pressure units — usually psi or barg in the field and kPa in calculations.
Always track whether a value is absolute or gauge: 0 barg equals about 101.3 kPa absolute, and mixing the two is a common and costly error.
Worked example. A pressure of 4014.631 inH₂O is 145.0377 psi.
Multiply the value in inH₂O by 0.03612729 to get psi. For example, 10 inH₂O = 0.3612729 psi.
1 inH₂O equals 0.03612729 psi.
Line and vessel ratings, pump discharge heads, and relief set points are all specified in pressure units — usually psi or barg in the field and kPa in calculations.