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Pressure

cmH₂OtoinH₂O

Convert centimetres of water column (cmH₂O) to inches of water column (4 °C) (inH₂O).

Factor1 cmH₂O = 0.3937008 inH₂O

Converter

cmH₂O

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

Result
3.93701inH₂O

Rendered to 6 significant figures.

Formula

Formula
inH₂O = cmH₂O × 0.3937008

Multiply any value in centimetres of water column by 0.3937008 to obtain the value in inches of water column (4 °C).

Worked example

Convert 10 cmH₂O to inH₂O.

  1. 01Start with 10 cmH₂O.
  2. 02Multiply by the conversion factor: 10 × 0.3937008 = 3.93701 inH₂O.
Result10 cmH₂O = 3.93701 inH₂O

Conversion table

cmH₂OinH₂O
10.3937
20.7874
51.9685
103.937
207.874
5019.685
10039.37
20078.74
500196.85
1000393.7

Reference values rounded to 5 significant figures for display.

FAQ

What is the conversion factor from cmH₂O to inH₂O?
1 cmH₂O equals 0.3937008 inH₂O. To convert, multiply the value in centimetres of water column by 0.3937008.
How do I convert 1 cmH₂O to inH₂O?
1 cmH₂O = 0.393701 inH₂O. For any value, multiply by 0.3937008.
How do I convert inH₂O back to cmH₂O?
Divide by the same factor — or equivalently, multiply by 2.54. So 1 inH₂O = 2.54 cmH₂O.
When would I need to convert centimetre of water column to inch of water column (4 °C)?
Pressure conversions between cmH₂O and inH₂O 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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