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Pressure

inH₂OtomH₂O

Convert inches of water column (4 °C) (inH₂O) to metres of water column (mH₂O).

Factor1 inH₂O = 0.0254 mH₂O

Converter

inH₂O

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

Result
2.54mH₂O

Rendered to 6 significant figures.

Formula

Formula
mH₂O = inH₂O × 0.0254

Multiply any value in inches of water column (4 °C) by 0.0254 to obtain the value in metres of water column.

Worked example

Convert 100 inH₂O to mH₂O.

  1. 01Start with 100 inH₂O.
  2. 02Multiply by the conversion factor: 100 × 0.0254 = 2.54 mH₂O.
Result100 inH₂O = 2.54 mH₂O

Conversion table

inH₂OmH₂O
10.0254
20.0508
50.127
100.254
200.508
501.27
1002.54
2005.08
50012.7
100025.4

Reference values rounded to 5 significant figures for display.

FAQ

What is the conversion factor from inH₂O to mH₂O?
1 inH₂O equals 0.0254 mH₂O. To convert, multiply the value in inches of water column (4 °C) by 0.0254.
How do I convert 1 inH₂O to mH₂O?
1 inH₂O = 0.0254 mH₂O. For any value, multiply by 0.0254.
How do I convert mH₂O back to inH₂O?
Divide by the same factor — or equivalently, multiply by 39.37008. So 1 mH₂O = 39.3701 inH₂O.
When would I need to convert inch of water column (4 °C) to metre of water column?
Pressure conversions between inH₂O and mH₂O 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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