Low pressures in gas lines, HVAC ducts and draft gauges are measured in inches of water column. One psi is about 27.7 inH₂O, and household natural gas runs at about 7 inH₂O (0.25 psi).
How to use the PSI to Inches of Water Converter
- Type the number of psi into the Psi field. Decimals such as 0.5 are fine.
- Read the answer in Inches of water – it updates as you type, with no button to press.
- To convert the other way, type into Inches of water and the psi are recalculated.
- Press Copy results to copy both values with the page title, or Copy link to share this exact conversion.
This page converts only psi ⇄ inH₂O. Need a different unit? Use the general pressure converter, where you can choose any “from” and “to” unit.
How it works
Both units measure pressure, so they are always in the same ratio: one pound per square inch equals 27.679905 inches of water. The calculator multiplies the number of psi you type by 27.679905 to give inches of water, and when you type into the inches of water field it divides by the same factor to give psi. Because the ratio never changes, doubling the psi always doubles the inches of water. Results are calculated at full precision and rounded only for display (up to eight decimal places, with very large or small values shown in scientific notation).
How to convert psi to inches of water
- Write down the value in psi, for example 1 psi.
- Multiply by the conversion factor 27.679905 (because 1 pound per square inch = 27.679905 inH₂O).
- 1 × 27.679905 = 27.679905 inH₂O.
- To go back from inches of water to psi, divide by 27.679905 – or multiply by 0.036127292.
psi to inH₂O conversion table
| Psi | Inches of water | Inches of water | Psi |
|---|---|---|---|
| 0.1 psi | 2.7679905 inH₂O | 1 inH₂O | 0.036127292 psi |
| 0.25 psi | 6.9199762 inH₂O | 2 inH₂O | 0.072254584 psi |
| 0.5 psi | 13.839952 inH₂O | 5 inH₂O | 0.18063646 psi |
| 1 psi | 27.679905 inH₂O | 10 inH₂O | 0.36127292 psi |
| 2 psi | 55.359809 inH₂O | 20 inH₂O | 0.72254584 psi |
| 5 psi | 138.39952 inH₂O | 50 inH₂O | 1.8063646 psi |
| 10 psi | 276.79905 inH₂O | 100 inH₂O | 3.6127292 psi |
| 1,000 inH₂O | 36.127292 psi |
What is a pound per square inch?
Pounds per square inch is the pressure of one pound-force on one square inch, about 6,895 Pa. U.S. tyre gauges, compressors and hydraulic equipment read psi.
What is an inch of water?
Inches of water column measure small pressures such as gas-line pressure, duct static pressure and chimney draft.
Quick mental conversion
For a fast estimate, multiply psi by about 28 to get inches of water; the error is about 1.2%. Use the calculator above when you need the exact figure.
Common mistakes to avoid
Mixing gauge pressure (psig, barg) with absolute pressure (psia, bara), treating bar and atm as identical, and confusing kgf/cm² with bar.
Formula
1 psi = 27.679905 inH₂O1 inH₂O = 0.036127292 psiinH₂O = psi × 27.679905Worked example
Inputs — Psi: 1 psi.
Results — Inches of water = 27.67990471 inH₂O.
Frequently asked questions
How many inches of water in 1 psi?
About 27.68 inH₂O.
What is typical residential gas pressure?
About 7 inH₂O, roughly 0.25 psi.
How do I convert psi to inches of water?
Multiply the number of psi by 27.679905. For example, 1 psi × 27.679905 = 27.679905 inH₂O.
How do I convert inches of water back to psi?
Divide by 27.679905 (or multiply by 0.036127292), or simply type the value into the inches of water field above.
What is 10 psi in inches of water?
10 psi = 276.79905 inH₂O.
What is 5 psi in inches of water?
5 psi = 138.39952 inH₂O.
Is this conversion exact?
Yes. The factor comes from the official definitions of both units (NIST and the SI), so the only difference you may see is rounding in the last displayed digit.
Can I convert to other units on this page?
This page converts only between psi and inches of water. To pick any pressure unit, use the general pressure converter linked under Related calculators.
What formula does the PSI to Inches of Water Converter use?
1 psi = 27.679905 inH₂O.