cmH2O – Centimetres of Water Column at 4 deg C Pressure Unit

Centimeters of Water Column is a manometric unit used to relate a pressure reading to the height of fresh water at a temperature of 4 degC. 1 centimeter of water gauge equals 98.0665 pascals.

The cmH2O pressure unit is mostly used to measure breathing on respirators and ventilators which are used in medical and physiological applications such as controlling respiratory conditions or monitoring athletic performance.

There are many ways of writing centimeters of water, but the cause of most confusion are Water Column (WC) and Water Gauge (WG), which both mean exactly the same thing.

For more details on metric water gauge pressure units please see our mWG page.

Please refer to the table below to find the value of 1 cmWC in another pressure unit.

To find the amount of cmWC in a different pressure unit please click on the approriate unit hyperlink in the table below.

Use our website pressure converter to convert multiple values of cmH2o.

Examine how cmH2O is calculated from SI units or check the the different ways of writing mmH2O.

Contents

Conversion Factors

0.000980665 bar
0.0142233 psi
0.980665 mbar
98.0665 N/m²
98.0665 Pa
0.980665 hPa
0.0980665 kPa
0.0000980665 MPa
0.001 kg/cm²
10 mmH2O 4°C (39.2°F)
1 cmH2O 4°C (39.2°F)
0.01 mH2O 4°C (39.2°F)
0.393701 inH2O 4°C (39.2°F)
0.0328084 ftH2O 4°C (39.2°F)
0.735559 mmHg 0°C (32°F)
0.0735559 cmHg 0°C (32°F)
0.0289590 inHg 0°C (32°F)
0.735559 Torr
735.559 mTorr
0.000967841 atm
0.001 at
980.665 dyn/cm²
0.227573 oz/in²
735.559 µHg 0°C (32°F)
0.00000634971 tsi (uk, long)
0.00000711167 tsi (usa, short)
0.00102408 tsf (usa, short)
2.04816 psf
1 g/cm²

Please note that the conversion factors above are accurate to 6 significant figures.

Derivation

The calculation below shows how the pressure unit Centimetres of Water Column (cmH2O) is derived from SI Units.

Formula

Pressure = Force / Area
Force = Mass x Acceleration
Mass = Density x Volume
Volume = Area x Height
Acceleration = Distance / (Second x Second)

SI Units

Mass: kilogram (kg)
Length: metre (m)
Time: second (s)
Force: newton (N)
Pressure: pascal (Pa)

Input Values

Density = Water Density at 4degC = 1000 kg/m³
Area = 1 m²
Height = 1 cm = 0.01 m
Acceleration = Standard Gravity = 9.80665 m/s²

Calculation

1 cmH2O Mass = 1000 kg/m³ x 1 m² x 0.01 m = 10 kg
1 cmH2O Force = 10 kg x 9.80665 m/s² = 98.0665 N
1 cmH2O Pressure = 98.0665 N / 1 m² = 98.0665 Pa

Alternate Descriptions

These are the different versions used for identifying cmH2O that you may find elsewhere.

Centimetres of H2O
Centimeters of H2O
Centimetres of Water Column
Centimeters of Water Column
Centimetres of Water Gauge
Centimeters of Water Gauge
cmH2O
cmWC
cmWG
cmWS
cmAq
cm H2O
cm WC
cm WG
cm WS
cm Aq
cmsH2O
cmsAq
cms H2O
cms Aq

Help

How does cmH2O differ at 4°C & 20°C

What is the difference between cmH₂O @ 4 deg C and cmH₂O @ 20 deg C?

The difference in pressure relates to the change in density of water between the two temperatures:

@4degC = 1000 kg/m³
@20degC = 998.2 kg/m³

Therefore a hydrostatic pressure of 1 cmH2O @20degC = 998.20/1000 cmH₂O @4degC = 0.9982 cmH₂O @4degC.

1.5 cmH2O to bar

How much pressure in bar do you need to generate a water pressure of 1.50 cmH2O?