The standard atmosphere (atm) is a unit of pressure defined as exactly 101,325 Pascals. It represents the average atmospheric pressure at sea level on Earth and is used as a fundamental reference in chemistry and physics.
| Unit Name | Symbol | Equivalent Value | System |
|---|---|---|---|
| Standard Atmosphere | atm | 1 | Base |
| Bar | bar | 1.01325 | Metric |
| Pascal | Pa | 101,325 | SI |
| Pound-force per sq inch | psi | 14.6959 | Imperial |
| Millimeters of Mercury | mmHg | 760 | Metric |
The bar is a metric unit of pressure defined as exactly 100,000 Pascals. Because it is very close to the atmospheric pressure at sea level, it is widely used in meteorology and engineering.
| Unit Name | Symbol | Equivalent Value | System |
|---|---|---|---|
| Standard Atmosphere | atm | 0.986923 | Base |
| Bar | bar | 1 | Metric |
| Pascal | Pa | 100,000 | SI |
| Pound-force per sq inch | psi | 14.5038 | Imperial |
| Millimeters of Mercury | mmHg | 750.062 | Metric |
The Pascal (Pa) is the SI derived unit of pressure, defined as one newton per square meter (1 N/m²). It is the standard in scientific research and materials science.
| Unit Name | Symbol | Equivalent Value | System |
|---|---|---|---|
| Standard Atmosphere | atm | 9.8692 × 10⁻⁶ | Base |
| Bar | bar | 1 × 10⁻⁵ | Metric |
| Pascal | Pa | 1 | SI |
| Pound-force per sq inch | psi | 1.45038 × 10⁻⁴ | Imperial |
| Millimeters of Mercury | mmHg | 0.00750062 | Metric |
PSI is a unit of pressure resulting from a force of one pound-force applied to an area of one square inch. It is widely used in the US for automotive, hydraulic systems, and industrial applications.
| Unit Name | Symbol | Equivalent Value | System |
|---|---|---|---|
| Standard Atmosphere | atm | 0.068046 | Base |
| Bar | bar | 0.0689476 | Metric |
| Pascal | Pa | 6,894.76 | SI |
| Pound-force per sq inch | psi | 1 | Imperial |
| Millimeters of Mercury | mmHg | 51.7149 | Metric |
mmHg is a manometric unit of pressure, formerly defined as the extra pressure generated by a column of mercury one millimeter high. Today, it is primarily used in medicine (blood pressure) and physiology.
| Unit Name | Symbol | Equivalent Value | System |
|---|---|---|---|
| Standard Atmosphere | atm | 0.00131579 | Base |
| Bar | bar | 0.00133322 | Metric |
| Pascal | Pa | 133.322 | SI |
| Pound-force per sq inch | psi | 0.0193368 | Imperial |
| Millimeters of Mercury | mmHg | 1 | Metric |