This page converts inches of water into kilopounds per square inch using the factor 3.612729055e-05, and shows the reverse figure alongside it. Both units measure pressure, which is why one number does the whole job.
One thousand psi; the unit US steel and alloy strengths are quoted in. The low-pressure unit for duct static pressure and gas appliances in the US.
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. Two tables follow: rounded steps for quick lookup, and a set of real reference quantities converted into kilopounds per square inch, which is usually more useful than the bare number.
The formula
inches of water- The amount you are converting, in inches of water
3.61272905497e-05- The exact number of kilopounds per square inch in one inch of water
kilopounds per square inch- The converted result
How it works, step by step
- Enter the value in inches of water.
- It is multiplied by 3.61272905497e-05, the exact factor between the two units.
- The answer is shown in kilopounds per square inch, with the reverse conversion beneath it.
- Check the reference table if you want a figure of comparable size.
Worked examples
A car tyre: 886 inH₂O in kilopounds per square inch
A car tyre comes to about 886 inH₂O. Multiplying by the factor: 886 × 3.61273e-05 = 0.0320088 ksi. Dividing the answer back by 3.61273e-05 returns the figure you started with, which is the quickest way to check you have the factor the right way up.
A steam boiler: 4010 inH₂O in kilopounds per square inch
Take a steam boiler, roughly 4010 inH₂O. The conversion is a single multiplication — 4010 × 3.61273e-05 — giving 0.14487 ksi. Because the relationship is proportional, doubling the input doubles the answer to 0.289741 ksi.
How to read your score
Frequently asked questions
How many kilopounds per square inch are in one inch of water?
Exactly 3.61272905497e-05. 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 kilopounds per square inch?
kilopounds per square inch = inches of water × 3.61272905497e-05. Reversed, inches of water = kilopounds per square inch ÷ 3.61272905497e-05, which is the same as multiplying by 27,679.9058214.
Which is the bigger unit, the inch of water or the kilopound per square inch?
The kilopound per square inch. One inch of water is only 3.61273e-05 of a kilopound per square inch, so it takes 27,679.9 inches of water to make one kilopound per square inch.
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 kilopound per square inch?
One thousand psi; the unit US steel and alloy strengths are quoted 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 ksi in my head?
Plenty of people do this in their head: divide by 28,000 instead of using the exact factor 0.000036. At 100 that shortcut gives 0.0035714286 kilopounds per square inch, off by 0.000041 kilopounds per square inch or about 1.14%. Fine for a rough estimate, not fine for anything you are cutting to size or dosing.
Inches Of Water to kilopounds per square inch reference tables
| Inches Of Water | Kilopounds Per Square Inch |
|---|---|
| 0.5 inH₂O | 1.80636e-05 ksi |
| 1 inH₂O | 3.61273e-05 ksi |
| 2 inH₂O | 7.22546e-05 ksi |
| 3 inH₂O | 0.000108382 ksi |
| 5 inH₂O | 0.000180636 ksi |
| 10 inH₂O | 0.000361273 ksi |
| 20 inH₂O | 0.000722546 ksi |
| 25 inH₂O | 0.000903182 ksi |
| 50 inH₂O | 0.00180636 ksi |
| 75 inH₂O | 0.00270955 ksi |
| 100 inH₂O | 0.00361273 ksi |
| 250 inH₂O | 0.00903182 ksi |
| 500 inH₂O | 0.0180636 ksi |
| 1000 inH₂O | 0.0361273 ksi |
| 5000 inH₂O | 0.180636 ksi |
Exact factor: 1 inch of water = 3.61272905497e-05 kilopounds per square inch.
| Quantity | inH₂O | ksi |
|---|---|---|
| Sea-level air | 406.8 inH₂O | 0.0147 ksi |
| A car tyre | 885.8 inH₂O | 0.032 ksi |
| Blood pressure, systolic | 64.23 inH₂O | 0.00232 ksi |
| A bicycle tyre | 2491 inH₂O | 0.09 ksi |
| A domestic water main | 1606 inH₂O | 0.05802 ksi |
| A steam boiler | 4015 inH₂O | 0.145 ksi |
Published reference values, converted with the same factor this page uses.