Pascal (unit)

Common multiples and everyday usage

Because the pascal is a small unit, practical work usually employs multiples such as the hectopascal (hPa, 100 Pa) and the kilopascal (kPa, 1 000 Pa). Meteorological air-pressure reports typically use hectopascals; standard sea-level atmospheric pressure is about 1013.25 hPa. Engineering, building services and tyre specifications commonly use kilopascals, while high stresses and material strengths are often expressed in megapascals (MPa). For accessible background on atmospheric values see typical atmospheric pressure references.

History and name

The unit is named after the French scientist and philosopher French savant mathematician and physicist Blaise Pascal, who in the 17th century made important contributions to hydrostatics and the study of fluids. His work underpins the concept that pressure in a fluid transmits equally in all directions (Pascal's law), a principle often cited in contexts where pressure and force transmission are relevant.

Measurement and instruments

Pressure in pascals is measured with instruments such as manometers, mercury or aneroid barometers for atmospheric observations, and electronic pressure transducers or strain-gauge sensors in industrial and laboratory applications. Instruments report results in Pa or convenient multiples; in many applied fields results are also converted to non‑SI units for compatibility with legacy practice.

Applications and examples

The pascal is used across meteorology, mechanical engineering, materials science and HVAC design because it connects directly to SI base quantities. Examples include air-pressure maps in hPa for weather forecasting, tyre pressures listed in kPa, and structural stress or concrete strength described in MPa. In medicine and physiology, non‑SI units such as millimetres of mercury remain common for clinical practice, though research often uses SI units including pascals.

Conversions and quick reference

• 1 Pa = 1 N·m−2 (one newton per square metre)
• 1 hPa = 100 Pa
• 1 kPa = 1 000 Pa
• 1 bar = 100 000 Pa (100 kPa)
• 1 standard atmosphere ≈ 101 325 Pa (≈1013.25 hPa)
• 1 psi ≈ 6 895 Pa (approximate, imperial unit)

The pascal provides a consistent SI-based way to express pressure and stress across scientific disciplines and engineering practice, facilitating comparison and calculation when combined with other SI units of force, length and mass.