Barometric Pressure Converter

Barometric pressure, also called atmospheric pressure, is the force exerted by the weight of the atmosphere above a given point on Earth. It is measured using a barometer and varies with altitude, weather patterns, and temperature. At sea level, standard barometric pressure is defined as 1 atm (101,325 Pa or 29.92 inHg).

Hectopascals (hPa) and millibars (mbar) are numerically identical — 1 hPa equals exactly 1 mbar. Meteorologists traditionally used millibars, but the modern SI-based unit is hectopascals. You will often see weather maps labeled in either unit interchangeably.

Multiply the inHg value by 33.8639 to get hPa. For example, the standard sea-level pressure of 29.92 inHg equals 29.92 × 33.8639 ≈ 1013.25 hPa. This converter does that math automatically for you.

Multiply the bar value by 1000 to get hectopascals, since 1 bar equals exactly 1000 hPa (or 100,000 Pa). For example, 1.01325 bar equals 1013.25 hPa, which is standard sea-level pressure.

Standard atmospheric pressure at sea level is defined as 1 atm = 101,325 Pa = 1013.25 hPa = 1013.25 mbar = 760 mmHg = 29.9213 inHg = 14.6959 psi. Weather forecasters consider 1013–1015 hPa a normal reading, with higher values indicating fair weather and lower values indicating stormy conditions.

The unit used depends largely on regional convention. The United States and some aviation contexts traditionally use inches of mercury (inHg), while meteorologists in most of the world and scientific communities use hectopascals (hPa) or millibars (mbar). Aviation also uses hPa/mbar for altimeter settings outside North America.

A falling barometric pressure generally signals approaching storms, rain, or unsettled weather. A rapid drop of more than 3–4 hPa per hour is considered a strong indicator of an incoming low-pressure system. Conversely, rising pressure typically signals clearing skies and fairer conditions.

To convert kilopascals to bar, divide by 100. So 210 kPa equals 210 ÷ 100 = 2.1 bar. Note that 210 kPa is well above normal atmospheric pressure and would represent something like a pressurized system rather than ambient barometric pressure.