What is a Pascal?

The pascal is the SI unit of pressure, equal to 1 newton per square meter (1 N/m²). Named after French mathematician and physicist Blaise Pascal (1623–1662), it became the SI standard in 1971. One pascal is a very small pressure: atmospheric pressure at sea level is about 101,325 Pa, the human breath exerts roughly 100 Pa above ambient, and tire pressure is in the hundreds of thousands of pascals. Because the pascal is small, the kilopascal (1 kPa = 1,000 Pa), megapascal (1 MPa = 10⁶ Pa), and gigapascal (1 GPa = 10⁹ Pa) are more commonly used in practice. Modern weather forecasts use hectopascals (1 hPa = 100 Pa = 1 millibar). The pascal relates to the bar (1 bar = 100,000 Pa), the psi (1 psi ≈ 6,895 Pa), the atmosphere (1 atm = 101,325 Pa), and mmHg (1 mmHg ≈ 133.3 Pa). Scientific and engineering publications use the pascal universally.

Visual reference for how the pascal relates to other pressure units. Each row links to the full converter for that pair.

• Scientific and engineering calculations
• Ventilation and HVAC airflow pressures
• Acoustic pressure (sound) measurements

• ✓1 Pa = 1 N/m².
• ✓1 kPa = 1000 Pa; 1 MPa = 1,000,000 Pa; 1 bar = 100,000 Pa.
• ✓Use kPa, MPa or bar for practical engineering work.

• ✗Confusing Pa with psi — 1 psi = 6895 Pa.
• ✗Using Pa for tyre pressures — 220,000 Pa unwieldy; use 2.2 bar.
• ✗Mixing Pa absolute and Pa gauge without specification.