Pressure Converter

How It Works

Pressure is force per unit area. This converter uses the Pascal (Pa) as its base unit — the SI unit of pressure, defined as one Newton per square meter (1 N/m²). Every other pressure unit stores its value in Pascals.

The Pascal is quite small. Standard atmospheric pressure at sea level is 101,325 Pa — often written as 1 atmosphere (atm) or 1.01325 bar. For engineering and industrial use, the kilopascal (kPa = 1,000 Pa) and megapascal (MPa = 1,000,000 Pa) are more practical.

The bar was introduced as a convenient near-atmospheric unit. 1 bar = 100,000 Pa (slightly less than 1 atm). Weather forecasters traditionally use millibars (mbar = 0.001 bar = 100 Pa); low-pressure storm systems might drop to 960 mbar, while high-pressure systems can reach 1,040 mbar.

PSI (pounds per square inch) is the dominant pressure unit in the US. 1 psi = 6,894.76 Pa. Common applications: car tyre pressure is typically 30–35 psi (207–241 kPa); blood pressure is measured in mmHg (normal: under 120/80 mmHg).

Millimeters of mercury (mmHg), also called Torr, originated with Torricelli's mercury barometer (1643). Standard atmospheric pressure supports a column of mercury 760 mm tall, so 1 atm = 760 mmHg = 101,325 Pa. Medical blood pressure and vacuum gauges still use mmHg.

Inches of mercury (inHg) is used in US aviation weather reports and some home barometers. Standard pressure = 29.92 inHg = 760 mmHg = 1 atm.

Worked example — Car tyre inflation:
32 psi = 32 × 6,894.76 Pa = 220,632 Pa = 220.6 kPa = 2.206 bar.

Worked example — Deep-sea pressure:
Every 10 meters of seawater adds approximately 1 atm of pressure. At 100 m depth: gauge pressure ≈ 10 atm = 1,013,250 Pa = 1,013.25 kPa ≈ 147 psi.

Worked example — Atmospheric reading:
A weather station records 1,013.25 mbar = 101,325 Pa = 29.92 inHg = 1 atm = 760 mmHg.