Inches of Water to PSI Converter
Convert inches of water column (in H2O, in w.c.) to psi. Divide inches by 27.68, or multiply by 0.0361.
Enter a value to convert
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How It Works
In North America, gas appliance rating plates, regulators and manometers read in inches of water, while gauges on higher-pressure gas piping read in psi. Converting lets you check one against the other: an appliance asking for 7 in w.c. needs about 0.25 psi at its inlet.
The unit is defined in water, so no specific gravity applies. An inch of water is the same pressure whether the line carries natural gas, propane or air.
Formula
psi = in H2O × 0.0361273
This uses the conventional inch of water, 249.089 Pa (1,000 kg/m³ under standard gravity). Dividing by 27.6799 gives the same result.
Worked Example
A propane regulator is set to 11 in w.c.:
11 × 0.0361273 = 0.3974 psi
Inches of Water to PSI Table
| in H2O | psi | mbar |
|---|---|---|
| 0.5 in H2O | 0.0180636 psi | 1.24544 mbar |
| 1 in H2O | 0.0361273 psi | 2.49089 mbar |
| 2 in H2O | 0.0722546 psi | 4.98178 mbar |
| 3.5 in H2O | 0.126446 psi | 8.71811 mbar |
| 5 in H2O | 0.180636 psi | 12.4544 mbar |
| 7 in H2O | 0.252891 psi | 17.4362 mbar |
| 10 in H2O | 0.361273 psi | 24.9089 mbar |
| 11 in H2O | 0.3974 psi | 27.3998 mbar |
| 14 in H2O | 0.505782 psi | 34.8724 mbar |
| 20 in H2O | 0.722546 psi | 49.8178 mbar |
| 28 in H2O | 1.01156 psi | 69.7449 mbar |
Going the other way? Use the psi to inches of water converter. For duct airflow, use the air flow calculator.
FAQ
Common questions about converting inches of water to psi.
Frequently Asked Questions
How do I convert inches of water to psi?
Multiply by 0.0361273, or divide by 27.6799. For example, 7 in w.c. is 0.252891 psi.
How many psi is 1 inch of water?
0.0361273 psi on the conventional basis.
Is 14 inches of water half a psi?
Close to it. 14 in w.c. is 0.505782 psi, and half a psi is 13.84 in w.c.
How do I convert inches of water to pascals?
Multiply by 249.089. A duct static pressure of 0.5 in w.c. is 124.544 Pa.
What is the difference between in H2O, in w.c. and inWC?
None. They are three ways of writing inches of water column, the pressure under one inch of water.
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