Kilopascals to Millimeters Of Water (kPa to mmH₂O)

1 kilopascal equals 101.9716213 millimeters of water (rounded).

How to convert kilopascals to millimeters of water

To convert kilopascals to millimeters of water, multiply the number of kilopascals by 101.9716213. The factor is rounded to 10 significant digits. To go the other way, multiply millimeters of water by 0.00980665.

millimeters of water = kilopascals × 101.9716213

Example: 10 kilopascals = 1,019.716213 millimeters of water.

About these units

Kilopascal (kPa)

Metric (SI)Current unit

1,000 pascals. Used for tire pressures, weather reports in many countries and engineering.

Kilopascal is the form of the pascal that most people actually use. The pascal itself is very small, so outside meteorology the kilopascal became the common choice in most fields, and it equals one centibar. Medical elastography reports tissue stiffness in kPa, and Canada reports atmospheric pressure in kPa rather than hectopascals.

A standard atmosphere is 101.325 kPa. In 1982 IUPAC recommended a different reference for chemistry, a standard pressure of exactly 100 kPa, which split the older convention of 1 atm into two competing standards.

Blood pressure shows how the units line up. One mmHg is 0.13332 kPa, and a normal reading is below about 16.0 kPa systolic and 10.7 kPa diastolic, the same thing as the familiar 120 over 80 in millimeters of mercury.

1 kilopascal = 1,000 pascals (exactly).

Sources: Wikipedia: Pascal (unit); Wikipedia: Standard atmosphere (unit); Wikipedia: Millimetre of mercury

Millimeter Of Water (mmH₂O)

ScientificCurrent unit

Exactly 9.80665 pascals by convention. Used for very low pressures.

A column of water one millimetre tall presses down with 9.80665 Pa under the usual convention, which assumes a density of 1,000 kg/m3 for water at its densest, near 4 degrees Celsius, and standard gravity. NIST marks this conventional millimeter of water as an exact factor. Using the true density of water at 4 degrees Celsius, 999.972 kg/m3, gives about 9.80638 Pa instead, so the two differ in the fifth digit.

Because the unit is so small it suits very low pressures, such as the draft in a duct or a chimney, filter drops and sensitive gauges. It also gives waterproof ratings for fabric, where a tent or jacket rated to some number of millimetres can resist that height of water before leaking. Pressure in this form is often written mmH2O, mmWG or mmWC. Ten millimetres of water is about 98 Pa, or roughly 0.1 percent of one standard atmosphere.

1 millimeter of water = 9.80665 pascals (exactly).

Sources: Wikipedia: Millimetre of water; NIST SP 811, Appendix B.8

Related conversions

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