To convert centimeters of water to millitorr, multiply by 735.5592401. 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 unit ventilator and CPAP pressures are set in. 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 millitorr, so you can sanity-check whether your answer is a plausible size.
The formula
centimeters of water- The amount you are converting, in centimeters of water
735.559240069- The exact number of millitorr in one centimeter of water
millitorr- The converted result
How it works, step by step
- Enter the value in centimeters of water.
- It is multiplied by 735.559240069, the exact factor between the two units.
- The answer is shown in millitorr, with the reverse conversion beneath it.
- Check the reference table if you want a figure of comparable size.
Worked examples
A car tyre: 2250 cmH₂O in millitorr
Take a car tyre, roughly 2250 cmH₂O. The conversion is a single multiplication — 2250 × 735.559 — giving 1.65501e+06 mTorr. Because the relationship is proportional, doubling the input doubles the answer to 3.31002e+06 mTorr.
A bicycle tyre: 6330 cmH₂O in millitorr
Take a bicycle tyre, roughly 6330 cmH₂O. The conversion is a single multiplication — 6330 × 735.559 — giving 4.65609e+06 mTorr. Because the relationship is proportional, doubling the input doubles the answer to 9.31218e+06 mTorr.
How to read your score
Frequently asked questions
How many millitorr are in one centimeter of water?
Exactly 735.559240069. 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 centimeters of water to millitorr?
millitorr = centimeters of water × 735.559240069. Reversed, centimeters of water = millitorr ÷ 735.559240069, which is the same as multiplying by 0.00135950980632.
Which is the bigger unit, the centimeter of water or the millitorr?
The centimeter of water. One centimeter of water equals 735.559 millitorr.
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 centimeter of water?
The unit ventilator and CPAP pressures are set in.
What is a millitorr?
One thousandth of a torr, the working unit of vacuum deposition.
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 cmH₂O to mTorr in my head?
Plenty of people do this in their head: multiply by 740 instead of using the exact factor 735.5592401. At 100 that shortcut gives 74,000 millitorr, off by 444.1 millitorr or about 0.60%. Fine for a rough estimate, not fine for anything you are cutting to size or dosing.
Centimeters Of Water to millitorr reference tables
| Centimeters Of Water | Millitorr |
|---|---|
| 0.5 cmH₂O | 367.78 mTorr |
| 1 cmH₂O | 735.559 mTorr |
| 2 cmH₂O | 1471.12 mTorr |
| 3 cmH₂O | 2206.68 mTorr |
| 5 cmH₂O | 3677.8 mTorr |
| 10 cmH₂O | 7355.59 mTorr |
| 20 cmH₂O | 14,711.2 mTorr |
| 25 cmH₂O | 18,389 mTorr |
| 50 cmH₂O | 36,778 mTorr |
| 75 cmH₂O | 55,166.9 mTorr |
| 100 cmH₂O | 73,555.9 mTorr |
| 250 cmH₂O | 183,890 mTorr |
| 500 cmH₂O | 367,780 mTorr |
| 1000 cmH₂O | 735,559 mTorr |
| 5000 cmH₂O | 3.6778e+06 mTorr |
Exact factor: 1 centimeter of water = 735.559240069 millitorr.
| Quantity | cmH₂O | mTorr |
|---|---|---|
| Sea-level air | 1033 cmH₂O | 7.6e+05 mTorr |
| A car tyre | 2250 cmH₂O | 1.655e+06 mTorr |
| Blood pressure, systolic | 163.1 cmH₂O | 1.2e+05 mTorr |
| A bicycle tyre | 6328 cmH₂O | 4.654e+06 mTorr |
| A domestic water main | 4079 cmH₂O | 3e+06 mTorr |
| A steam boiler | 1.02e+04 cmH₂O | 7.501e+06 mTorr |
Published reference values, converted with the same factor this page uses.