To convert inches of water to feet of water, multiply by 0.08333333055. 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 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. The tables underneath give both a plain step-by-step lookup and a list of real quantities expressed in feet of water, so you can sanity-check whether your answer is a plausible size.
The formula
inches of water- The amount you are converting, in inches of water
0.0833333305454- The exact number of feet of water in one inch of water
feet of water- The converted result
How it works, step by step
- Enter the value in inches of water.
- It is multiplied by 0.0833333305454, the exact factor between the two units.
- The answer is shown in feet of water, with the reverse conversion beneath it.
- Check the reference table if you want a figure of comparable size.
Worked examples
A bicycle tyre: 2490 inH₂O in feet of water
Take a bicycle tyre, roughly 2490 inH₂O. The conversion is a single multiplication — 2490 × 0.0833333 — giving 207.5 ftH₂O. Because the relationship is proportional, doubling the input doubles the answer to 415 ftH₂O.
Blood pressure, systolic: 64.2 inH₂O in feet of water
At 64.2 inH₂O (blood pressure, systolic), the same quantity in feet of water is 64.2 × 0.0833333 = 5.35 ftH₂O. One inch of water is 0.0833333 feet of water, so the numbers shrink as expected.
How to read your score
Frequently asked questions
How many feet of water are in one inch of water?
Exactly 0.0833333305454. 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 feet of water?
feet of water = inches of water × 0.0833333305454. Reversed, inches of water = feet of water ÷ 0.0833333305454, which is the same as multiplying by 12.0000004015.
Which is the bigger unit, the inch of water or the foot of water?
The foot of water. One inch of water is only 0.0833333 of a foot of water, so it takes 12 inches of water to make one foot 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 inch of water?
The low-pressure unit for duct static pressure and gas appliances in the US.
What is a foot of water?
Pump head expressed as a column of water — the way pump curves are drawn.
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 ftH₂O in my head?
Plenty of people do this in their head: divide by 12 instead of using the exact factor 0.08333333055. At 100 that shortcut gives 8.3333333 feet of water, off by 0.000000 feet of water or about 0.00%. Fine for a rough estimate, not fine for anything you are cutting to size or dosing.
Inches Of Water to feet of water reference tables
| Inches Of Water | Feet Of Water |
|---|---|
| 0.5 inH₂O | 0.0416667 ftH₂O |
| 1 inH₂O | 0.0833333 ftH₂O |
| 2 inH₂O | 0.166667 ftH₂O |
| 3 inH₂O | 0.25 ftH₂O |
| 5 inH₂O | 0.416667 ftH₂O |
| 10 inH₂O | 0.833333 ftH₂O |
| 20 inH₂O | 1.66667 ftH₂O |
| 25 inH₂O | 2.08333 ftH₂O |
| 50 inH₂O | 4.16667 ftH₂O |
| 75 inH₂O | 6.25 ftH₂O |
| 100 inH₂O | 8.33333 ftH₂O |
| 250 inH₂O | 20.8333 ftH₂O |
| 500 inH₂O | 41.6667 ftH₂O |
| 1000 inH₂O | 83.3333 ftH₂O |
| 5000 inH₂O | 416.667 ftH₂O |
Exact factor: 1 inch of water = 0.0833333305454 feet of water.
| Quantity | inH₂O | ftH₂O |
|---|---|---|
| Sea-level air | 406.8 inH₂O | 33.9 ftH₂O |
| A car tyre | 885.8 inH₂O | 73.81 ftH₂O |
| Blood pressure, systolic | 64.23 inH₂O | 5.352 ftH₂O |
| A bicycle tyre | 2491 inH₂O | 207.6 ftH₂O |
| A domestic water main | 1606 inH₂O | 133.8 ftH₂O |
| A steam boiler | 4015 inH₂O | 334.6 ftH₂O |
Published reference values, converted with the same factor this page uses.