What Is Hectopascal (hPa)?
A hectopascal, written as hPa, is a unit that tells us how strong air or another fluid is pressing on a surface. It is a way to measure pressure. Weather forecasts often use hectopascals to show air pressure at different places on Earth.
Definition
Pressure is force acting on an area. The basic pressure unit in the International System of Units is the pascal, which is 1 newton of force pressing on 1 square meter of area.
One hectopascal means 100 pascals. So:
- 1 hPa = 100 Pa
When you see a weather map that shows numbers like 1013 hPa, that number is telling you how much the air above is pressing down on the ground at that spot.
History / Origin
The hectopascal comes from two parts. The word pascal comes from Blaise Pascal, a French scientist from the 1600s who studied pressure and fluids. The prefix hecto comes from Greek and means one hundred.
First, scientists used the unit pascal as the main pressure unit in the metric system. Later, they added prefixes like hecto to make the numbers easier to read. In weather science, people used to use the millibar. Over time, many weather services changed from millibar to hectopascal because it fits better with the modern SI system.
Today, the hectopascal is really just the same size as the old millibar, but with a new name that matches the pascal system.
Symbol & Abbreviation
The unit name is hectopascal.
- Full name: hectopascal
- Symbol: hPa
The symbol always uses a small h and capital P and small a. You write the number first, then a space, then the symbol. For example:
- 1013 hPa
- 950 hPa
- 500 hPa
Current Use Around the World
The hectopascal is widely used for weather and climate work.
Main uses include:
- Weather reports TV, radio, apps, and websites show air pressure in hPa.
- Weather maps Lines of equal pressure on maps, called isobars, are labeled in hPa.
- Aviation Pilots set their altimeters using pressure values that are often given in hPa.
- Climate research Scientists use hPa when they study the atmosphere and make models.
Many regions, including most of Europe, Asia, Australia, and other countries that follow the metric system, use hPa in their official weather services. In some places like the United States, people may still talk about inches of mercury in daily life, but meteorologists also use hPa in professional work.
Example Conversions
Here are some useful conversions between hectopascal and other common pressure units.
Between hPa and Pa
- 1 hPa = 100 Pa
- 1000 hPa = 100 000 Pa
Between hPa and kilopascal kPa
- 1 hPa = 0.1 kPa
- 10 hPa = 1 kPa
- 1013 hPa ≈ 101.3 kPa
Between hPa and millibar mbar
- 1 hPa = 1 mbar exactly in practical use
- 1013 hPa = 1013 mbar
This is why older weather charts in millibars look the same as newer ones in hectopascals.
Between hPa and standard atmosphere atm
- Standard sea level pressure ≈ 1013 hPa ≈ 1 atm
- 1 atm ≈ 1013.25 hPa
Between hPa and pounds per square inch psi
- 1 hPa ≈ 0.0145 psi
- 1000 hPa ≈ 14.5 psi
- 1013 hPa ≈ 14.7 psi about normal air pressure at sea level
Related Units
The hectopascal is part of a family of pressure units. Here are some that are closely related or often used together.
- Pascal Pa The main SI unit of pressure. 1 hPa = 100 Pa.
- Kilopascal kPa 1000 pascals. Often used in engineering. 1 hPa = 0.1 kPa.
- Millibar mbar Very close in size to the hPa. 1 mbar = 1 hPa in practice.
- Bar A larger pressure unit. 1 bar = 1000 hPa.
- Standard atmosphere atm About the average air pressure at sea level. 1 atm ≈ 1013.25 hPa.
- Torr Used in vacuum science. 760 torr ≈ 1013 hPa.
- Pounds per square inch psi Often used for car tires in some countries. 1 psi ≈ 69 hPa.
FAQs
Q. What is a hectopascal in simple words
A. A hectopascal is a way to measure how strongly air is pushing on a surface. It is often used in weather reports to show air pressure.
Q. Is hPa the same as millibar
A. For almost all practical uses, yes. 1 hPa equals 1 millibar, so old values in millibars can be read as hPa without changing the numbers.
Q. What hPa value is normal air pressure at sea level
A. Normal or standard air pressure at sea level is about 1013 hPa. Weather reports often compare higher or lower pressure to this value.
Q. Why do weather maps use hPa instead of Pa
A. If we used pascals, the numbers would be very large, around 100 000 Pa. Using hectopascals makes the numbers shorter and easier to read, around 1000 hPa.
Q. How can I convert hPa to kPa quickly
A. Divide the hPa value by 10. For example, 1020 hPa becomes 102.0 kPa, and 980 hPa becomes 98.0 kPa.
Q. How can I convert hPa to psi in my head
A. You can use an easy rule. First divide the hPa value by 70. This gives a rough psi value. For example, 700 hPa is about 10 psi, and 1400 hPa is about 20 psi.
Q. Where will I most often see hPa in daily life
A. You will most often see hPa in weather apps, weather websites, and TV forecasts. Pilots and meteorologists also work with hPa all the time.