To convert feet of water to pounds per square foot, multiply by 62.42796016. That factor is the whole relationship: both units measure pressure, so the conversion is a proportion with no offset and no substance-specific constant.
Pump head expressed as a column of water — the way pump curves are drawn. 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. The tables underneath give both a plain step-by-step lookup and a list of real quantities expressed in pounds per square foot, so you can sanity-check whether your answer is a plausible size.
The formula
feet of water- The amount you are converting, in feet of water
62.4279601584- The exact number of pounds per square foot in one foot of water
pounds per square foot- The converted result
How it works, step by step
- Enter the value in feet of water.
- It is multiplied by 62.4279601584, 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
Blood pressure, systolic: 5.35 ftH₂O in pounds per square foot
At 5.35 ftH₂O (blood pressure, systolic), the same quantity in pounds per square foot is 5.35 × 62.428 = 333.99 psf. One foot of water is 62.428 pounds per square foot, so the numbers grow as expected.
A steam boiler: 335 ftH₂O in pounds per square foot
A steam boiler comes to about 335 ftH₂O. Multiplying by the factor: 335 × 62.428 = 20,913.4 psf. Dividing the answer back by 62.428 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 pounds per square foot are in one foot of water?
Exactly 62.4279601584. 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 pounds per square foot?
pounds per square foot = feet of water × 62.4279601584. Reversed, feet of water = pounds per square foot ÷ 62.4279601584, which is the same as multiplying by 0.0160184634811.
Which is the bigger unit, the foot of water or the pound per square foot?
The foot of water. One foot of water equals 62.428 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 foot of water?
Pump head expressed as a column of water — the way pump curves are drawn.
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 ftH₂O to psf in my head?
Plenty of people do this in their head: multiply by 60 instead of using the exact factor 62.42796016. At 100 that shortcut gives 6000 pounds per square foot, off by 242.8 pounds per square foot or about 3.89%. Fine for a rough estimate, not fine for anything you are cutting to size or dosing.
Feet Of Water to pounds per square foot reference tables
| Feet Of Water | Pounds Per Square Foot |
|---|---|
| 0.5 ftH₂O | 31.214 psf |
| 1 ftH₂O | 62.428 psf |
| 2 ftH₂O | 124.856 psf |
| 3 ftH₂O | 187.284 psf |
| 5 ftH₂O | 312.14 psf |
| 10 ftH₂O | 624.28 psf |
| 20 ftH₂O | 1248.56 psf |
| 25 ftH₂O | 1560.7 psf |
| 50 ftH₂O | 3121.4 psf |
| 75 ftH₂O | 4682.1 psf |
| 100 ftH₂O | 6242.8 psf |
| 250 ftH₂O | 15,607 psf |
| 500 ftH₂O | 31,214 psf |
| 1000 ftH₂O | 62,428 psf |
| 5000 ftH₂O | 312,140 psf |
Exact factor: 1 foot of water = 62.4279601584 pounds per square foot.
| Quantity | ftH₂O | psf |
|---|---|---|
| Sea-level air | 33.9 ftH₂O | 2116 psf |
| A car tyre | 73.81 ftH₂O | 4608 psf |
| Blood pressure, systolic | 5.352 ftH₂O | 334.1 psf |
| A bicycle tyre | 207.6 ftH₂O | 1.296e+04 psf |
| A domestic water main | 133.8 ftH₂O | 8354 psf |
| A steam boiler | 334.6 ftH₂O | 2.089e+04 psf |
Published reference values, converted with the same factor this page uses.