One standard atmosphere equals 14.7 psi (29.92 in. -Hg). Any fraction of an atmosphere is a partial vacuum and equates with negative gauge pressure. A torr is defined as 1/760 of an atmosphere and can also be thought of as 1 mm-Hg, where 760 mm-Hg equals 29.92 in. -Hg.

What are the rules (sign conventions) to use S.I units?

• Those units which are named after the name of scientists are always written with their first or initial letter being non-capitalized.
• The symbols used for the units which are named after the name of any scientist should be written by a capital letter.

Centimeters of Mercury is a small pressure unit which represents the pressure pushing down due to gravity of any volume of liquid mercury which is 1cm high. 1 centimeter of mercury at zero degrees Celsius equals 1333.22 pascals.

inHg to mmHg Conversion Table

1. 1 mmHg = 133.322 pascals (Pa)
2. 1 inHg = 3386.39 pascals (Pa)
3. mmHg value x 133.322 Pa = inHg value x 3386.39 Pa.
4. mmHg value = inHg value x 25.4.

1 kilogram per cubic meter (kg/m3) = 0.43 psi per 1000 feet (psi/1000 ft)

To convert millibars to inches of mercury, multiply the millibar value by 0.0295301.

To convert 28 inches of mercury to atmospheres, divide 28 by the 29.92. This yields a result of 0.936 atmosphere. To convert back to inches, multiply 0.936 by 29.92. The conversion requires adjustment at temperatures higher or lower than zero degrees Celsius.

A more reliable and common unit is millimeters of mercury (mmHg), which is the amount of pressure exerted by a column of mercury exactly 1 mm high.