What is hectopascal?
A hectopascal is a pressure unit equal to 100 pascals, numerically identical to the millibar. It is the standard unit for atmospheric pressure reports in modern meteorology and aviation weather data.
Real-world uses
Hectopascals are the modern meteorological standard for atmospheric pressure reporting, used by the World Meteorological Organization and most national weather services. Standard atmospheric pressure is 1013.25 hPa. Altimeter settings in aviation outside the US use hPa (QNH).
History
The hectopascal was promoted by the WMO beginning in 1982 as a replacement for the millibar, aligning meteorology with the SI system. Since 1 hPa equals exactly 1 mbar, the transition required no changes to numerical readings or instruments.
Common mistakes
Not realizing that 1 hPa = 1 mbar exactly. The switch from millibars to hectopascals changed only the name, not the numerical values. Also, some people confuse hPa with kPa; 1 kPa = 10 hPa.
What is pound per square inch?
Pound per square inch (psi) is an imperial pressure unit widely used in the United States for tire inflation, hydraulic system pressures, gas cylinder ratings, and plumbing specifications.
Real-world uses
PSI is the standard pressure unit in the United States for tyre inflation (typically 30–35 psi for cars), compressed air tools, hydraulic systems, and water pressure. HVAC systems, fire extinguisher ratings, and pressure cooker specifications use psi in North America.
History
Pounds per square inch emerged naturally from the Imperial/US customary system, combining the pound-force with the square inch. It became the dominant pressure unit in American industry and remains deeply embedded in US engineering standards and building codes.
Common mistakes
Not distinguishing between psi (absolute, psia) and psig (gauge, relative to atmosphere). A tyre reading of 32 psig actually means about 46.7 psia. Also, confusing psi with kPa when using equipment from metric countries.
When is this conversion used?
Converting between hectopascal and pound per square inch is common when working across metric and imperial systems, such as international trade, travel between countries with different measurement standards, or following instructions from a different region. Tyre pressure gauges, HVAC systems, and industrial equipment may use different pressure units depending on the manufacturer and region. Converting between psi, bar, and kPa is common in automotive and engineering work.
Worked examples
1 hectopascal = 0.01450377 pound per square inch
1 pound per square inch = 6,894.75729317 pascal
How to convert hectopascal to pound per square inch
To convert hectopascal to pound per square inch, multiply the value by 0.01450377.
To convert pound per square inch back to hectopascal, multiply by 68.94757293.
Measurement standards
The pascal (Pa) is the SI derived unit of pressure, defined as one newton per square metre. The World Meteorological Organization mandates the hectopascal (hPa) for atmospheric pressure reporting in aviation and weather services.
Did you know?
The pressure at the bottom of the Mariana Trench, nearly 11 km deep, exceeds 1,086 bar — over a thousand times atmospheric pressure. At this depth, water is compressed by about 5%, making it measurably denser than at the surface.
Quick reference: hectopascal to pound per square inch
| hectopascal | pound per square inch |
|---|---|
| 0.1 | 0.00145038 |
| 0.5 | 0.00725189 |
| 1 | 0.01450377 |
| 2 | 0.02900755 |
| 5 | 0.07251887 |
| 10 | 0.14503774 |
| 25 | 0.36259434 |
| 50 | 0.72518869 |
| 100 | 1.45037738 |
| 250 | 3.62594344 |
| 500 | 7.25188689 |
| 1,000 | 14.50377377 |
Common values
| hectopascal | pound per square inch | |
|---|---|---|
| Car tyre | 2,200 hectopascal | 31.9083023 pound per square inch |
| Standard atmosphere | 1,013.25 hectopascal | 14.69594878 pound per square inch |
| Blood pressure (systolic) | 160 hectopascal | 2.3206038 pound per square inch |
| Deep-sea submersible | 1,100,000 hectopascal | 15,954.15115032 pound per square inch |
| Bicycle tyre | 6,200 hectopascal | 89.92339739 pound per square inch |