Centimeters of water to millimeters of mercury
Type a value in centimeters of water to see it in millimeters of mercury straight away, or type in the second box to convert back.
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How to use it
- Type the value in the centimeters of water box.
- Read the result in millimeters of mercury as you type, and pick the precision you need.
- Swap the direction to convert back, or copy the result.
How it is calculated
mmHg = cmH₂O × 0.7355591353
Multiply the value in centimeters of water by 0.7355591353 to get millimeters of mercury.
Example
To convert 25 cmH₂O to millimeters of mercury: 25 × 0.7355591353 = 18.389 mmHg.
Conversion table
| Centimeters of water (cmH₂O) | Millimeters of mercury (mmHg) |
|---|---|
| 1 | 0.735559 |
| 2 | 1.47112 |
| 3 | 2.20668 |
| 5 | 3.6778 |
| 10 | 7.35559 |
| 20 | 14.7112 |
| 25 | 18.389 |
| 50 | 36.778 |
| 100 | 73.5559 |
| 250 | 183.89 |
| 500 | 367.78 |
| 1,000 | 735.559 |
About the units
- Centimeter of water
- The pressure of a 1 cm water column at conventional density and standard gravity: 98.0665 Pa. Common on ventilators and CPAP machines.
- Millimeter of mercury
- The pressure of a 1 mm mercury column at the conventional density 13,595.1 kg/m³ and standard gravity: 133.322387415 Pa. Used for blood pressure.
Limits and caveats
- Results are rounded for display and computed with the browser's floating point precision (about 15 significant digits).
- Both unit factors are exact by their official definitions.
Questions about this tool
How many millimeters of mercury are in one centimeter of water?
1 cmH₂O = 0.735559 mmHg exactly.
How do I convert centimeters of water to millimeters of mercury?
Use mmHg = cmH₂O × 0.7355591353. For example, 25 cmH₂O = 18.389 mmHg.
How many centimeters of water are in one millimeter of mercury?
1 mmHg = 1.35951 cmH₂O.
What is the difference between gauge and absolute pressure?
Gauge pressure is measured from the surrounding air pressure, while absolute pressure starts from a perfect vacuum. These converters change the unit only, so a gauge reading stays a gauge reading.
Are torr and mmHg the same?
Almost. One torr is 101325/760 Pa, about 133.322368 Pa, and one conventional mmHg is 133.322387 Pa, a difference of less than one part per million. For everyday use you can treat them as equal.