Like other measurements, pressure is represented in units. The International System of Measurements (SI) uses the pascal as the standard unit of measure for pressure. Other countries, like the United States of America, that do not use the SI unit of measure might use the bar or pounds per square inch as the primary unit of measure for pressure.
Meteorologists will use the millibar and hectopascal when referring to atmospheric pressure, although the inch of mercury is still used in the United States. Pressure is often expressed by a length measurement of displaced liquid such as millimeter of mercury or inch of water. The most common types of liquid used are mercury and water. Pressure can be measured by how much liquid is displaced in a cylinder, but can vary from one column to the next do to local factors.
Since there are such a wide range of units used for measuring pressure, converting between them can be extremely difficult. You can use our pressure conversion calculator to convert between the most commonly used units of pressure along with a few you probably have never heard of before. Simply choose which unit you know and what measurement you want to convert to. Enter the amount in the form field and our converter will do the rest.