To convert millitorr to inches of water, multiply by 0.0005352401027. 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 low-pressure unit for duct static pressure and gas appliances in the US. One thousandth of a torr, the working unit of vacuum deposition.
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 inches of water, so you can sanity-check whether your answer is a plausible size.
The formula
millitorr- The amount you are converting, in millitorr
0.000535240102715- The exact number of inches of water in one millitorr
inches of water- The converted result
How it works, step by step
- Enter the value in millitorr.
- It is multiplied by 0.000535240102715, the exact factor between the two units.
- The answer is shown in inches of water, with the reverse conversion beneath it.
- Check the reference table if you want a figure of comparable size.
Worked examples
A steam boiler: 7.5e+06 mTorr in inches of water
Take a steam boiler, roughly 7.5e+06 mTorr. The conversion is a single multiplication — 7.5e+06 × 0.00053524 — giving 4014.3 inH₂O. Because the relationship is proportional, doubling the input doubles the answer to 8028.6 inH₂O.
A car tyre: 1.65e+06 mTorr in inches of water
A car tyre comes to about 1.65e+06 mTorr. Multiplying by the factor: 1.65e+06 × 0.00053524 = 883.146 inH₂O. Dividing the answer back by 0.00053524 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 inches of water are in one millitorr?
Exactly 0.000535240102715. 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 inches of water?
inches of water = millitorr × 0.000535240102715. Reversed, millitorr = inches of water ÷ 0.000535240102715, which is the same as multiplying by 1868.32039477.
Which is the bigger unit, the millitorr or the inch of water?
The inch of water. One millitorr is only 0.00053524 of a inch of water, so it takes 1868.32 millitorr to make one inch 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 inch of water?
The low-pressure unit for duct static pressure and gas appliances in the US.
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 inH₂O in my head?
Plenty of people do this in their head: divide by 1900 instead of using the exact factor 0.0005352401027. At 100 that shortcut gives 0.052631579 inches of water, off by 0.0008924 inches of water or about 1.67%. Fine for a rough estimate, not fine for anything you are cutting to size or dosing.
Millitorr to inches of water reference tables
| Millitorr | Inches Of Water |
|---|---|
| 0.5 mTorr | 0.00026762 inH₂O |
| 1 mTorr | 0.00053524 inH₂O |
| 2 mTorr | 0.00107048 inH₂O |
| 3 mTorr | 0.00160572 inH₂O |
| 5 mTorr | 0.0026762 inH₂O |
| 10 mTorr | 0.0053524 inH₂O |
| 20 mTorr | 0.0107048 inH₂O |
| 25 mTorr | 0.013381 inH₂O |
| 50 mTorr | 0.026762 inH₂O |
| 75 mTorr | 0.040143 inH₂O |
| 100 mTorr | 0.053524 inH₂O |
| 250 mTorr | 0.13381 inH₂O |
| 500 mTorr | 0.26762 inH₂O |
| 1000 mTorr | 0.53524 inH₂O |
| 5000 mTorr | 2.6762 inH₂O |
Exact factor: 1 millitorr = 0.000535240102715 inches of water.
| Quantity | mTorr | inH₂O |
|---|---|---|
| Sea-level air | 7.6e+05 mTorr | 406.8 inH₂O |
| A car tyre | 1.655e+06 mTorr | 885.8 inH₂O |
| Blood pressure, systolic | 1.2e+05 mTorr | 64.23 inH₂O |
| A bicycle tyre | 4.654e+06 mTorr | 2491 inH₂O |
| A domestic water main | 3e+06 mTorr | 1606 inH₂O |
| A steam boiler | 7.501e+06 mTorr | 4015 inH₂O |
Published reference values, converted with the same factor this page uses.