What is normal barometric pressure at sea level?

Standard sea-level pressure is 1013.25 hPa (also 1013.25 mbar, 29.92 inHg, 760 mmHg, 1.0 atm, or 101.325 kPa). Actual readings vary with weather and altitude.

What is the difference between hPa and mbar?

Hectopascal (hPa) and millibar (mbar) are numerically identical — 1 hPa = 1 mbar. The hPa designation is now preferred in meteorology under the SI unit system, but both are in widespread use.

How is barometric pressure related to weather?

High pressure (above ~1020 hPa) generally brings clear, settled weather. Low pressure (below ~1000 hPa) is associated with clouds, rain, and storms. A rapidly falling pressure often signals an approaching storm.

Why does altitude affect barometric pressure?

The atmosphere becomes thinner with altitude. At higher elevations there is less air mass above you, so pressure drops. Pressure decreases roughly 12 hPa per 100 m gain near sea level.

What unit do US weather stations use?

US surface weather reports and home barometers traditionally use inches of mercury (inHg). International and aviation reports typically use hPa or mbar.

Barometric Pressure Converter

Name: Barometric Pressure Converter
Availability: InStock
Author: Nham Vu

Enter a pressure value in any unit and instantly convert it to hPa, mbar, inHg, mmHg, atm, and kPa, with a weather-condition indicator.

Enter Pressure

Input Unit

Pressure Value

Quick Presets

Converted Values

Enter a pressure value to see conversions

Common Pressure Reference Points

Condition	hPa	inHg	mmHg
Standard atmosphere	1013.25	29.92	760.0
Very high pressure	1040	30.71	780.1
Fair weather	1020	30.12	765.1
Changeable	1000	29.53	750.1
Stormy	980	28.94	735.1

Copied!

Summary

Enter a pressure value in any unit and instantly convert it to hPa, mbar, inHg, mmHg, atm, and kPa, with a weather-condition indicator.

How it works

Select the unit of your source pressure reading.
Enter the pressure value in the input field.
All five remaining units are computed immediately using exact conversion factors.
A weather-condition badge appears based on the equivalent hPa value.
Use the Copy button next to any result to copy that value to your clipboard.

Use cases

Convert barometer readings between metric and imperial units.
Check aviation METAR or altimeter settings in the correct unit for your instrument.
Understand weather forecast pressure values reported in unfamiliar units.
Convert scientific data between SI units (kPa, hPa) and legacy units (inHg, mmHg).
Assess current weather tendency by comparing pressure to typical fair-weather values.

Frequently Asked Questions

Last updated: 2026-05-23 · Reviewed by Nham Vu