How the Pressure Converter Works

A pressure converter translates a pressure reading between common units such as pascal (Pa), kilopascal (kPa), bar, psi (pounds per square inch), atmosphere (atm) and millimeters of mercury (mmHg). Pressure is force applied over an area, and the SI base unit is the pascal, defined as one newton per square meter.

Because a single pascal is tiny, real-world pressures are usually expressed in larger units like kilopascals or bar. Each unit relates to the pascal by a fixed factor, so the converter simply rescales your value. Whether you are checking tire pressure in psi, reading a weather barometer in mmHg, or working with industrial systems in bar, the same reference factors apply.

Pressure Conversion Factors

All pressure units can be defined relative to the pascal. Here are the exact and standard factors:

• 1 kilopascal (kPa) = 1,000 Pa
• 1 bar = 100,000 Pa = 100 kPa
• 1 atmosphere (atm) = 101,325 Pa = 101.325 kPa = 1.01325 bar
• 1 psi = 6,894.76 Pa ≈ 6.895 kPa
• 1 atm = 14.696 psi
• 1 mmHg (torr) = 133.322 Pa
• 1 atm = 760 mmHg

For example, to convert 2 bar to psi: 2 bar × 100,000 Pa ÷ 6,894.76 Pa = 29.0 psi. To convert standard atmospheric pressure to kilopascals, simply note that 1 atm = 101.325 kPa.

Common Pressure Conversions

This reference table lists frequently used pressure values across all six units, anchored on one standard atmosphere.

Unit	Value (= 1 atm)
Pascal (Pa)	101,325
Kilopascal (kPa)	101.325
Bar	1.01325
Psi	14.696
Atmosphere (atm)	1
mmHg (torr)	760

These equivalences come from the definition of the standard atmosphere, which approximates average air pressure at sea level. Bar and atmosphere are close in size but not identical, so for precise work use the exact factor 1 atm = 1.01325 bar.

Where Each Pressure Unit Is Used

Different fields favor different units. The pascal and kilopascal dominate in science and engineering because they are SI units. Bar is common in European industry, hydraulics and weather reports. Psi is the everyday unit in the United States for tires, compressors and plumbing.

Atmospheres appear in chemistry and diving, while mmHg (also called torr) is standard in medicine for blood pressure and in barometry. Knowing the right factor lets you move confidently between these contexts. Since all units trace back to the pascal, you can chain any two conversions through it for a reliable result.

Absolute vs Gauge Pressure

One subtlety worth knowing is the difference between absolute and gauge pressure, because it affects how you interpret a converted value. Absolute pressure is measured relative to a perfect vacuum, while gauge pressure is measured relative to the surrounding atmospheric pressure. The relationship is simple: absolute pressure = gauge pressure + atmospheric pressure (about 101.325 kPa at sea level).

This matters in everyday situations. When you check your car tires and read 32 psi, that is gauge pressure, meaning 32 psi above the surrounding air. The absolute pressure inside the tire is actually about 32 + 14.7 = 46.7 psi. Units like psi are sometimes written as psig (gauge) or psia (absolute) to make the reference clear. The conversion factors stay the same regardless of which reference you use; only the starting value changes.

To avoid errors, always confirm whether a reading is gauge or absolute before converting, particularly in engineering, scuba diving and weather applications. A barometer reports absolute atmospheric pressure, while most industrial gauges report gauge pressure. Once you know the reference, the same fixed factors let you convert between pascal, bar, psi, atmospheres and mmHg accurately, every time.