One millitorr is exactly 4.46033404e-05 feet of water, so converting millitorr to feet of water is a single multiplication. Enter any figure and the result appears as you type — the arithmetic runs in your browser, so nothing is sent anywhere.
One thousandth of a torr, the working unit of vacuum deposition. 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. Below the calculator there is a step table for the values people look up most, and a second table putting real pressure figures into feet of water so the number you get has something to be compared against.
The formula
millitorr- The amount you are converting, in millitorr
4.46033404007e-05- The exact number of feet of water in one millitorr
feet of water- The converted result
How it works, step by step
- Enter the value in millitorr.
- It is multiplied by 4.46033404007e-05, 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 car tyre: 1.65e+06 mTorr in feet of water
At 1.65e+06 mTorr (a car tyre), the same quantity in feet of water is 1.65e+06 × 4.46033e-05 = 73.5955 ftH₂O. One millitorr is 4.46033e-05 feet of water, so the numbers shrink as expected.
A domestic water main: 3e+06 mTorr in feet of water
At 3e+06 mTorr (a domestic water main), the same quantity in feet of water is 3e+06 × 4.46033e-05 = 133.81 ftH₂O. One millitorr is 4.46033e-05 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 millitorr?
Exactly 4.46033404007e-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 millitorr to feet of water?
feet of water = millitorr × 4.46033404007e-05. Reversed, millitorr = feet of water ÷ 4.46033404007e-05, which is the same as multiplying by 22,419.8454873.
Which is the bigger unit, the millitorr or the foot of water?
The foot of water. One millitorr is only 4.46033e-05 of a foot of water, so it takes 22,419.8 millitorr 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 millitorr?
One thousandth of a torr, the working unit of vacuum deposition.
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 mTorr to ftH₂O in my head?
Plenty of people do this in their head: divide by 22,000 instead of using the exact factor 0.000045. At 100 that shortcut gives 0.0045454545 feet of water, off by 0.000085 feet of water or about 1.91%. Fine for a rough estimate, not fine for anything you are cutting to size or dosing.
Millitorr to feet of water reference tables
| Millitorr | Feet Of Water |
|---|---|
| 0.5 mTorr | 2.23017e-05 ftH₂O |
| 1 mTorr | 4.46033e-05 ftH₂O |
| 2 mTorr | 8.92067e-05 ftH₂O |
| 3 mTorr | 0.00013381 ftH₂O |
| 5 mTorr | 0.000223017 ftH₂O |
| 10 mTorr | 0.000446033 ftH₂O |
| 20 mTorr | 0.000892067 ftH₂O |
| 25 mTorr | 0.00111508 ftH₂O |
| 50 mTorr | 0.00223017 ftH₂O |
| 75 mTorr | 0.00334525 ftH₂O |
| 100 mTorr | 0.00446033 ftH₂O |
| 250 mTorr | 0.0111508 ftH₂O |
| 500 mTorr | 0.0223017 ftH₂O |
| 1000 mTorr | 0.0446033 ftH₂O |
| 5000 mTorr | 0.223017 ftH₂O |
Exact factor: 1 millitorr = 4.46033404007e-05 feet of water.
| Quantity | mTorr | ftH₂O |
|---|---|---|
| Sea-level air | 7.6e+05 mTorr | 33.9 ftH₂O |
| A car tyre | 1.655e+06 mTorr | 73.81 ftH₂O |
| Blood pressure, systolic | 1.2e+05 mTorr | 5.352 ftH₂O |
| A bicycle tyre | 4.654e+06 mTorr | 207.6 ftH₂O |
| A domestic water main | 3e+06 mTorr | 133.8 ftH₂O |
| A steam boiler | 7.501e+06 mTorr | 334.6 ftH₂O |
Published reference values, converted with the same factor this page uses.