This page converts pounds per square foot into inches of water using the factor 0.1922215682, and shows the reverse figure alongside it. Both units measure pressure, which is why one number does the whole job.
The low-pressure unit for duct static pressure and gas appliances in the US. The unit US building codes give floor, roof and wind loads in.
Gauge versus absolute. A tyre gauge reading 32 psi means 32 psi above atmospheric, which is about 46.7 psi absolute. Converting the number is straightforward; remembering which zero it was measured from is where the mistakes happen. N/mm² and MPa are the same size, so a drawing quoting either is quoting the same stress. Below the calculator there is a step table for the values people look up most, and a second table putting real pressure figures into inches of water so the number you get has something to be compared against.
The formula
pounds per square foot- The amount you are converting, in pounds per square foot
0.192221568205- The exact number of inches of water in one pound per square foot
inches of water- The converted result
How it works, step by step
- Enter the value in pounds per square foot.
- It is multiplied by 0.192221568205, the exact factor between the two units.
- The answer is shown in inches of water, with the reverse conversion beneath it.
- Check the reference table if you want a figure of comparable size.
Worked examples
Sea-level air: 2120 psf in inches of water
At 2120 psf (sea-level air), the same quantity in inches of water is 2120 × 0.192222 = 407.51 inH₂O. One pound per square foot is 0.192222 inches of water, so the numbers shrink as expected.
Blood pressure, systolic: 334 psf in inches of water
Take blood pressure, systolic, roughly 334 psf. The conversion is a single multiplication — 334 × 0.192222 — giving 64.202 inH₂O. Because the relationship is proportional, doubling the input doubles the answer to 128.404 inH₂O.
How to read your score
Frequently asked questions
How many inches of water are in one pound per square foot?
Exactly 0.192221568205. Every figure on this page is that one number multiplied by your input, so the only rounding is at the display step.
What is the formula to convert pounds per square foot to inches of water?
inches of water = pounds per square foot × 0.192221568205. Reversed, pounds per square foot = inches of water ÷ 0.192221568205, which is the same as multiplying by 5.20232983916.
Which is the bigger unit, the pound per square foot or the inch of water?
The inch of water. One pound per square foot is only 0.192222 of a inch of water, so it takes 5.20233 pounds per square foot to make one inch of water.
What does this quantity actually measure?
Both units measure pressure. That is why a single factor is enough: there is no temperature offset and no material property involved, unlike conversions that cross between different quantities.
What is a pound per square foot?
The unit US building codes give floor, roof and wind loads in.
What is a inch of water?
The low-pressure unit for duct static pressure and gas appliances in the US.
Why does my answer differ from another converter?
Almost always because the other tool rounded the factor before multiplying. This page keeps full double precision through the calculation and rounds only for display, and it prints the factor it used so you can see where any difference came from.
Is there a quick way to do psf to inH₂O in my head?
Plenty of people do this in their head: divide by 5 instead of using the exact factor 0.1922215682. At 100 that shortcut gives 20 inches of water, off by 0.7778 inches of water or about 4.05%. Fine for a rough estimate, not fine for anything you are cutting to size or dosing.
Pounds Per Square Foot to inches of water reference tables
| Pounds Per Square Foot | Inches Of Water |
|---|---|
| 0.5 psf | 0.0961108 inH₂O |
| 1 psf | 0.192222 inH₂O |
| 2 psf | 0.384443 inH₂O |
| 3 psf | 0.576665 inH₂O |
| 5 psf | 0.961108 inH₂O |
| 10 psf | 1.92222 inH₂O |
| 20 psf | 3.84443 inH₂O |
| 25 psf | 4.80554 inH₂O |
| 50 psf | 9.61108 inH₂O |
| 75 psf | 14.4166 inH₂O |
| 100 psf | 19.2222 inH₂O |
| 250 psf | 48.0554 inH₂O |
| 500 psf | 96.1108 inH₂O |
| 1000 psf | 192.222 inH₂O |
| 5000 psf | 961.108 inH₂O |
Exact factor: 1 pound per square foot = 0.192221568205 inches of water.
| Quantity | psf | inH₂O |
|---|---|---|
| Sea-level air | 2116 psf | 406.8 inH₂O |
| A car tyre | 4608 psf | 885.8 inH₂O |
| Blood pressure, systolic | 334.1 psf | 64.23 inH₂O |
| A bicycle tyre | 1.296e+04 psf | 2491 inH₂O |
| A domestic water main | 8354 psf | 1606 inH₂O |
| A steam boiler | 2.089e+04 psf | 4015 inH₂O |
Published reference values, converted with the same factor this page uses.