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Pressure

mmHgtocmH₂O

Convert millimetres of mercury (mmHg) to centimetres of water column (cmH₂O).

Factor1 mmHg = 1.35951 cmH₂O

Converter

mmHg

Accepts numbers or expressions, e.g. 150 + 14.7

Result
135.951cmH₂O

Rendered to 6 significant figures.

Formula

Formula
cmH₂O = mmHg × 1.35951

Multiply any value in millimetres of mercury by 1.35951 to obtain the value in centimetres of water column.

Worked example

Convert 100 mmHg to cmH₂O.

  1. 01Start with 100 mmHg.
  2. 02Multiply by the conversion factor: 100 × 1.35951 = 135.951 cmH₂O.
Result100 mmHg = 135.951 cmH₂O

Conversion table

mmHgcmH₂O
11.3595
22.719
56.7976
1013.595
2027.19
5067.975
100135.95
200271.9
500679.75
10001359.5

Reference values rounded to 5 significant figures for display.

FAQ

What is the conversion factor from mmHg to cmH₂O?
1 mmHg equals 1.35951 cmH₂O. To convert, multiply the value in millimetres of mercury by 1.35951.
How do I convert 1 mmHg to cmH₂O?
1 mmHg = 1.35951 cmH₂O. For any value, multiply by 1.35951.
How do I convert cmH₂O back to mmHg?
Divide by the same factor — or equivalently, multiply by 0.7355591. So 1 cmH₂O = 0.735559 mmHg.
When would I need to convert millimetre of mercury to centimetre of water column?
Pressure conversions between mmHg and cmH₂O are common when working with mixed-vendor instrumentation, when piping codes use different units to process datasheets, or when converting field readings into SI for hydraulic calculations.
Is the conversion exact?
The factor shown is precise to at least 7 significant figures. For most process-engineering work this is far better than instrument accuracy. For metrology or trade applications, refer to the relevant national standard (NIST, BIPM, ISO 80000).

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