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Pressure

mH₂OtommHg

Convert metres of water column (mH₂O) to millimetres of mercury (mmHg).

Factor1 mH₂O = 73.55591 mmHg

Converter

mH₂O

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

Result
73.5559mmHg

Rendered to 6 significant figures.

Formula

Formula
mmHg = mH₂O × 73.55591

Multiply any value in metres of water column by 73.55591 to obtain the value in millimetres of mercury.

Worked example

Convert 1 mH₂O to mmHg.

  1. 01Start with 1 mH₂O.
  2. 02Multiply by the conversion factor: 1 × 73.55591 = 73.5559 mmHg.
Result1 mH₂O = 73.5559 mmHg

Conversion table

mH₂OmmHg
173.556
2147.11
5367.78
10735.56
201471.1
503677.8
1007355.6
20014711
50036778
100073556

Reference values rounded to 5 significant figures for display.

FAQ

What is the conversion factor from mH₂O to mmHg?
1 mH₂O equals 73.55591 mmHg. To convert, multiply the value in metres of water column by 73.55591.
How do I convert 1 mH₂O to mmHg?
1 mH₂O = 73.5559 mmHg. For any value, multiply by 73.55591.
How do I convert mmHg back to mH₂O?
Divide by the same factor — or equivalently, multiply by 0.0135951. So 1 mmHg = 0.0135951 mH₂O.
When would I need to convert metre of water column to millimetre of mercury?
Pressure conversions between mH₂O and mmHg 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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