To convert feet of water to kilopascals, multiply by 2.9890669. That factor is the whole relationship: both units measure pressure, so the conversion is a proportion with no offset and no substance-specific constant.
The standard tyre-pressure unit in metric countries. Pump head expressed as a column of water — the way pump curves are drawn.
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 kilopascals, which is usually more useful than the bare number.
The formula
feet of water- The amount you are converting, in feet of water
2.9890669- The exact number of kilopascals in one foot of water
kilopascals- The converted result
How it works, step by step
- Enter the value in feet of water.
- It is multiplied by 2.9890669, the exact factor between the two units.
- The answer is shown in kilopascals, with the reverse conversion beneath it.
- Check the reference table if you want a figure of comparable size.
Worked examples
A car tyre: 73.8 ftH₂O in kilopascals
At 73.8 ftH₂O (a car tyre), the same quantity in kilopascals is 73.8 × 2.98907 = 220.593 kPa. One foot of water is 2.98907 kilopascals, so the numbers grow as expected.
Sea-level air: 33.9 ftH₂O in kilopascals
Sea-level air comes to about 33.9 ftH₂O. Multiplying by the factor: 33.9 × 2.98907 = 101.329 kPa. Dividing the answer back by 2.98907 returns the figure you started with, which is the quickest way to check you have the factor the right way up.
How to read your score
Frequently asked questions
How many kilopascals are in one foot of water?
Exactly 2.9890669. 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 feet of water to kilopascals?
kilopascals = feet of water × 2.9890669. Reversed, feet of water = kilopascals ÷ 2.9890669, which is the same as multiplying by 0.334552565551.
Which is the bigger unit, the foot of water or the kilopascal?
The foot of water. One foot of water equals 2.98907 kilopascals.
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 foot of water?
Pump head expressed as a column of water — the way pump curves are drawn.
What is a kilopascal?
The standard tyre-pressure unit in metric countries.
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 ftH₂O to kPa in my head?
Plenty of people do this in their head: multiply by 3 instead of using the exact factor 2.9890669. At 100 that shortcut gives 300 kilopascals, off by 1.093 kilopascals or about 0.37%. Fine for a rough estimate, not fine for anything you are cutting to size or dosing.
Feet Of Water to kilopascals reference tables
| Feet Of Water | Kilopascals |
|---|---|
| 0.5 ftH₂O | 1.49453 kPa |
| 1 ftH₂O | 2.98907 kPa |
| 2 ftH₂O | 5.97813 kPa |
| 3 ftH₂O | 8.9672 kPa |
| 5 ftH₂O | 14.9453 kPa |
| 10 ftH₂O | 29.8907 kPa |
| 20 ftH₂O | 59.7813 kPa |
| 25 ftH₂O | 74.7267 kPa |
| 50 ftH₂O | 149.453 kPa |
| 75 ftH₂O | 224.18 kPa |
| 100 ftH₂O | 298.907 kPa |
| 250 ftH₂O | 747.267 kPa |
| 500 ftH₂O | 1494.53 kPa |
| 1000 ftH₂O | 2989.07 kPa |
| 5000 ftH₂O | 14,945.3 kPa |
Exact factor: 1 foot of water = 2.9890669 kilopascals.
| Quantity | ftH₂O | kPa |
|---|---|---|
| Sea-level air | 33.9 ftH₂O | 101.3 kPa |
| A car tyre | 73.81 ftH₂O | 220.6 kPa |
| Blood pressure, systolic | 5.352 ftH₂O | 16 kPa |
| A bicycle tyre | 207.6 ftH₂O | 620.5 kPa |
| A domestic water main | 133.8 ftH₂O | 400 kPa |
| A steam boiler | 334.6 ftH₂O | 1000 kPa |
Published reference values, converted with the same factor this page uses.