This page converts inches of water into pounds per square foot using the factor 5.202329839, 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 pounds per square foot so the number you get has something to be compared against.
The formula
inches of water- The amount you are converting, in inches of water
5.20232983916- The exact number of pounds per square foot in one inch of water
pounds per square foot- The converted result
How it works, step by step
- Enter the value in inches of water.
- It is multiplied by 5.20232983916, the exact factor between the two units.
- The answer is shown in pounds per square foot, with the reverse conversion beneath it.
- Check the reference table if you want a figure of comparable size.
Worked examples
A domestic water main: 1610 inH₂O in pounds per square foot
Take a domestic water main, roughly 1610 inH₂O. The conversion is a single multiplication — 1610 × 5.20233 — giving 8375.75 psf. Because the relationship is proportional, doubling the input doubles the answer to 16,751.5 psf.
Blood pressure, systolic: 64.2 inH₂O in pounds per square foot
At 64.2 inH₂O (blood pressure, systolic), the same quantity in pounds per square foot is 64.2 × 5.20233 = 333.99 psf. One inch of water is 5.20233 pounds per square foot, so the numbers grow as expected.
How to read your score
Frequently asked questions
How many pounds per square foot are in one inch of water?
Exactly 5.20232983916. 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 inches of water to pounds per square foot?
pounds per square foot = inches of water × 5.20232983916. Reversed, inches of water = pounds per square foot ÷ 5.20232983916, which is the same as multiplying by 0.192221568205.
Which is the bigger unit, the inch of water or the pound per square foot?
The inch of water. One inch of water equals 5.20233 pounds per square foot.
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 inch of water?
The low-pressure unit for duct static pressure and gas appliances in the US.
What is a pound per square foot?
The unit US building codes give floor, roof and wind loads in.
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 inH₂O to psf in my head?
Plenty of people do this in their head: multiply by 5 instead of using the exact factor 5.202329839. At 100 that shortcut gives 500 pounds per square foot, off by 20.23 pounds per square foot or about 3.89%. Fine for a rough estimate, not fine for anything you are cutting to size or dosing.
Inches Of Water to pounds per square foot reference tables
| Inches Of Water | Pounds Per Square Foot |
|---|---|
| 0.5 inH₂O | 2.60116 psf |
| 1 inH₂O | 5.20233 psf |
| 2 inH₂O | 10.4047 psf |
| 3 inH₂O | 15.607 psf |
| 5 inH₂O | 26.0116 psf |
| 10 inH₂O | 52.0233 psf |
| 20 inH₂O | 104.047 psf |
| 25 inH₂O | 130.058 psf |
| 50 inH₂O | 260.116 psf |
| 75 inH₂O | 390.175 psf |
| 100 inH₂O | 520.233 psf |
| 250 inH₂O | 1300.58 psf |
| 500 inH₂O | 2601.16 psf |
| 1000 inH₂O | 5202.33 psf |
| 5000 inH₂O | 26,011.6 psf |
Exact factor: 1 inch of water = 5.20232983916 pounds per square foot.
| Quantity | inH₂O | psf |
|---|---|---|
| Sea-level air | 406.8 inH₂O | 2116 psf |
| A car tyre | 885.8 inH₂O | 4608 psf |
| Blood pressure, systolic | 64.23 inH₂O | 334.1 psf |
| A bicycle tyre | 2491 inH₂O | 1.296e+04 psf |
| A domestic water main | 1606 inH₂O | 8354 psf |
| A steam boiler | 4015 inH₂O | 2.089e+04 psf |
Published reference values, converted with the same factor this page uses.