# Calculate Air Pressure with Barometer

A barometer is a measuring instrument that shows the air pressure and whether it means good or bad weather. However, the latter is only correct at sea level, as the pressure decreases with increasing altitude. 980 hPa means a decent low at sea level, but an impressive high at 500 meters. Therefore, barometers are often calibrated so that they do not show the true air pressure, but the corresponding air pressure at sea level. This calculator can also be used for this purpose. 1013.25 hectopascals (hPa) or millibars (mbar) are considered normal pressure.

If your barometer is calibrated at sea level (this is the default), then enter the measured value, the altitude of the location, and the temperature. The equivalent value at sea level and a color for estimating the weather will be displayed. The conversion is based on an average atmosphere. In extreme or special weather conditions, a different temperature gradient may apply.

A barometer calibrated to a different altitude can also be used with the calculator. Enter the corresponding height difference at Altitude. If the barometer is calibrated to a higher altitude, put a minus in front of the altitude value.

Barometer value: | hPa (mbar) |

Altitude: | meters |

Temperature: | °C |

Temperature gradient: | °C/m |

Equivalent air pressure (at sea level) : hPa (mbar)

-980 very low, stormy 980-1000 low, rainy 1000-1020 normal, changeable 1020-1040 high, sunny 1040- very high, very dry

The **temperature gradient** indicates how quickly the temperature falls with altitude. A good guess in normal weather is 0.0065 °C/meter.

**Temperature Estimation**: Sea level temperature = temperature + temperature gradient * altitude

**Barometric formula:**

Air pressure at sea level = barometer value / (1-temperature gradient*altitude/temperature at sea level in kelvins)^(0,03416/temperature gradient)

The barometric height formula describes how the density of the gas particles decreases as you go up. To put it simply, the pressure drops by one hectopascal for every eight meters up. In fact, however, the relationship is exponential.

Physics commonly uses SI units. Here is a calculator to convert lengths, temperature, pressure, speed and other units.