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Pressure

cmH₂Otoatm

Convert centimetres of water column (cmH₂O) to standard atmospheres (atm).

Factor1 cmH₂O = 0.0009678411 atm

Converter

cmH₂O

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

Result
0.967841atm

Rendered to 6 significant figures.

Formula

Formula
atm = cmH₂O × 0.0009678411

Multiply any value in centimetres of water column by 0.0009678411 to obtain the value in standard atmospheres.

Worked example

Convert 1000 cmH₂O to atm.

  1. 01Start with 1000 cmH₂O.
  2. 02Multiply by the conversion factor: 1000 × 0.0009678411 = 0.967841 atm.
Result1000 cmH₂O = 0.967841 atm

Conversion table

cmH₂Oatm
10.00096784
20.0019357
50.0048392
100.0096784
200.019357
500.048392
1000.096784
2000.19357
5000.48392
10000.96784

Reference values rounded to 5 significant figures for display.

FAQ

What is the conversion factor from cmH₂O to atm?
1 cmH₂O equals 0.0009678411 atm. To convert, multiply the value in centimetres of water column by 0.0009678411.
How do I convert 1 cmH₂O to atm?
1 cmH₂O = 0.000967841 atm. For any value, multiply by 0.0009678411.
How do I convert atm back to cmH₂O?
Divide by the same factor — or equivalently, multiply by 1033.227. So 1 atm = 1033.23 cmH₂O.
When would I need to convert centimetre of water column to standard atmosphere?
Pressure conversions between cmH₂O and atm 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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