This page converts centimeters of water into millimeters of mercury using the factor 0.7355591353, and shows the reverse figure alongside it. Both units measure pressure, which is why one number does the whole job.
The clinical unit for blood pressure worldwide. The unit ventilator and CPAP pressures are set in.
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 millimeters of mercury, 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
0.735559135277- The exact number of millimeters of mercury in one centimeter of water
millimeters of mercury- The converted result
How it works, step by step
- Enter the value in centimeters of water.
- It is multiplied by 0.735559135277, the exact factor between the two units.
- The answer is shown in millimeters of mercury, with the reverse conversion beneath it.
- Check the reference table if you want a figure of comparable size.
Worked examples
A domestic water main: 4080 cmH₂O in millimeters of mercury
A domestic water main comes to about 4080 cmH₂O. Multiplying by the factor: 4080 × 0.735559 = 3001.08 mmHg. Dividing the answer back by 0.735559 returns the figure you started with, which is the quickest way to check you have the factor the right way up.
Sea-level air: 1030 cmH₂O in millimeters of mercury
Take sea-level air, roughly 1030 cmH₂O. The conversion is a single multiplication — 1030 × 0.735559 — giving 757.626 mmHg. Because the relationship is proportional, doubling the input doubles the answer to 1515.25 mmHg.
How to read your score
Frequently asked questions
How many millimeters of mercury are in one centimeter of water?
Exactly 0.735559135277. 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 millimeters of mercury?
millimeters of mercury = centimeters of water × 0.735559135277. Reversed, centimeters of water = millimeters of mercury ÷ 0.735559135277, which is the same as multiplying by 1.35951.
Which is the bigger unit, the centimeter of water or the millimeter of mercury?
The millimeter of mercury. One centimeter of water is only 0.735559 of a millimeter of mercury, so it takes 1.35951 centimeters of water to make one millimeter of mercury.
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 millimeter of mercury?
The clinical unit for blood pressure worldwide.
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 mmHg in my head?
Plenty of people do this in their head: divide by 1.4 instead of using the exact factor 0.7355591353. At 100 that shortcut gives 71.428571 millimeters of mercury, off by 2.127 millimeters of mercury or about 2.89%. Fine for a rough estimate, not fine for anything you are cutting to size or dosing.
Centimeters Of Water to millimeters of mercury reference tables
| Centimeters Of Water | Millimeters Of Mercury |
|---|---|
| 0.5 cmH₂O | 0.36778 mmHg |
| 1 cmH₂O | 0.735559 mmHg |
| 2 cmH₂O | 1.47112 mmHg |
| 3 cmH₂O | 2.20668 mmHg |
| 5 cmH₂O | 3.6778 mmHg |
| 10 cmH₂O | 7.35559 mmHg |
| 20 cmH₂O | 14.7112 mmHg |
| 25 cmH₂O | 18.389 mmHg |
| 50 cmH₂O | 36.778 mmHg |
| 75 cmH₂O | 55.1669 mmHg |
| 100 cmH₂O | 73.5559 mmHg |
| 250 cmH₂O | 183.89 mmHg |
| 500 cmH₂O | 367.78 mmHg |
| 1000 cmH₂O | 735.559 mmHg |
| 5000 cmH₂O | 3677.8 mmHg |
Exact factor: 1 centimeter of water = 0.735559135277 millimeters of mercury.
| Quantity | cmH₂O | mmHg |
|---|---|---|
| Sea-level air | 1033 cmH₂O | 760 mmHg |
| A car tyre | 2250 cmH₂O | 1655 mmHg |
| Blood pressure, systolic | 163.1 cmH₂O | 120 mmHg |
| A bicycle tyre | 6328 cmH₂O | 4654 mmHg |
| A domestic water main | 4079 cmH₂O | 3000 mmHg |
| A steam boiler | 1.02e+04 cmH₂O | 7501 mmHg |
Published reference values, converted with the same factor this page uses.