This page converts feet of water into centimeters of water using the factor 30.4799998, and shows the reverse figure alongside it. Both units measure pressure, which is why one number does the whole job.
The unit ventilator and CPAP pressures are set in. 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 centimeters of water, which is usually more useful than the bare number.
The formula
feet of water- The amount you are converting, in feet of water
30.4799997961- The exact number of centimeters of water in one foot of water
centimeters of water- The converted result
How it works, step by step
- Enter the value in feet of water.
- It is multiplied by 30.4799997961, the exact factor between the two units.
- The answer is shown in centimeters of water, with the reverse conversion beneath it.
- Check the reference table if you want a figure of comparable size.
Worked examples
A domestic water main: 134 ftH₂O in centimeters of water
At 134 ftH₂O (a domestic water main), the same quantity in centimeters of water is 134 × 30.48 = 4084.32 cmH₂O. One foot of water is 30.48 centimeters of water, so the numbers grow as expected.
Blood pressure, systolic: 5.35 ftH₂O in centimeters of water
Take blood pressure, systolic, roughly 5.35 ftH₂O. The conversion is a single multiplication — 5.35 × 30.48 — giving 163.068 cmH₂O. Because the relationship is proportional, doubling the input doubles the answer to 326.136 cmH₂O.
How to read your score
Frequently asked questions
How many centimeters of water are in one foot of water?
Exactly 30.4799997961. 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 centimeters of water?
centimeters of water = feet of water × 30.4799997961. Reversed, feet of water = centimeters of water ÷ 30.4799997961, which is the same as multiplying by 0.0328083991697.
Which is the bigger unit, the foot of water or the centimeter of water?
The foot of water. One foot of water equals 30.48 centimeters 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 foot of water?
Pump head expressed as a column of water — the way pump curves are drawn.
What is a centimeter of water?
The unit ventilator and CPAP pressures are set 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 cmH₂O in my head?
Plenty of people do this in their head: multiply by 30 instead of using the exact factor 30.4799998. At 100 that shortcut gives 3000 centimeters of water, off by 48 centimeters of water or about 1.57%. Fine for a rough estimate, not fine for anything you are cutting to size or dosing.
Feet Of Water to centimeters of water reference tables
| Feet Of Water | Centimeters Of Water |
|---|---|
| 0.5 ftH₂O | 15.24 cmH₂O |
| 1 ftH₂O | 30.48 cmH₂O |
| 2 ftH₂O | 60.96 cmH₂O |
| 3 ftH₂O | 91.44 cmH₂O |
| 5 ftH₂O | 152.4 cmH₂O |
| 10 ftH₂O | 304.8 cmH₂O |
| 20 ftH₂O | 609.6 cmH₂O |
| 25 ftH₂O | 762 cmH₂O |
| 50 ftH₂O | 1524 cmH₂O |
| 75 ftH₂O | 2286 cmH₂O |
| 100 ftH₂O | 3048 cmH₂O |
| 250 ftH₂O | 7620 cmH₂O |
| 500 ftH₂O | 15,240 cmH₂O |
| 1000 ftH₂O | 30,480 cmH₂O |
| 5000 ftH₂O | 152,400 cmH₂O |
Exact factor: 1 foot of water = 30.4799997961 centimeters of water.
| Quantity | ftH₂O | cmH₂O |
|---|---|---|
| Sea-level air | 33.9 ftH₂O | 1033 cmH₂O |
| A car tyre | 73.81 ftH₂O | 2250 cmH₂O |
| Blood pressure, systolic | 5.352 ftH₂O | 163.1 cmH₂O |
| A bicycle tyre | 207.6 ftH₂O | 6328 cmH₂O |
| A domestic water main | 133.8 ftH₂O | 4079 cmH₂O |
| A steam boiler | 334.6 ftH₂O | 1.02e+04 cmH₂O |
Published reference values, converted with the same factor this page uses.