About

Atmospheric pressure is measured in a confusing array of units depending on the industry. Meteorologists prefer Hectopascals (hPa), aviation uses Inches of Mercury (inHg) or hPa, divers use Bars (bar), and engineers often work in PSI (psi). This fragmentation creates a need for a centralized conversion hub.

This tool is designed as a "One-to-Many" converter. By entering a value in Hectopascals - the standard SI derived unit for air pressure - the system simultaneously calculates the equivalent values across the pressure spectrum. It is particularly useful for students interpreting weather maps or engineers calibrating sensitive equipment. A built-in status indicator also compares the input against standard sea-level pressure (1013.25 hPa), giving immediate context to the data (e.g., "High Pressure System").

Formulas

Pressure P is Force F applied perpendicular to the surface of an object per unit area A.

P = FA

Conversion from Hectopascals (hPa):

To Pa: x × 100
To atm: x ÷ 1013.25
To psi: x × 0.01450377

Reference Data

Unit	Symbol	1 hPa Equals	Common Use
Pascal	Pa	100	Scientific SI Base
Kilopascal	kPa	0.1	Engineering
Bar	bar	0.001	Diving / Industrial
Millibar	mbar	1	Old Meteorology
Atmosphere	atm	0.0009869	Chemistry
Torr	Torr	0.75006	Vacuum Physics
Pounds/Sq Inch	psi	0.0145038	Automotive / Tires

Frequently Asked Questions

Standard atmospheric pressure at sea level is exactly 1013.25 hPa. Values significantly above this (e.g., >1020 hPa) indicate high pressure (fair weather), while values below (e.g., <1000 hPa) indicate low pressure (storms).

Yes. 1 Hectopascal is exactly equal to 1 Millibar. The term "Hectopascal" is preferred in modern SI standards, but "Millibar" persists in older literature and some broadcast meteorology.

Weather reports give "Sea Level Pressure" (adjusted for altitude). Your barometer measures "Absolute Pressure" at your specific location. Pressure drops as you go higher (approx 1 hPa per 8 meters).