Pressure Measurement · Glossary

What is Atmospheric Pressure?

about 1.013 bar at sea levelPressure Measurement

Atmospheric pressure is the pressure of the air around us; it falls with altitude and varies with weather.

Atmospheric Pressure Explained

Standard atmospheric pressure at sea level is 101.325 kPa. Actual values change by a few percent with weather and drop by about 11 % at 1000 m altitude.

Atmospheric pressure is the reference for gauge measurements and must be added to get absolute pressure.

Atmospheric Pressure Formula

p = 101.325 × (1 − 2.25577 × 10⁻⁵ × h)^5.25588 kPa

h	altitude above sea level (m)

Example: At 1000 m: p ≈ 89.9 kPa.

Calculators for Atmospheric Pressure

CalculatorAtmospheric Pressure at Altitude CalculatorFree online calculator with formula and worked example.CalculatorAbsolute Pressure CalculatorFree online calculator with formula and worked example.CalculatorBoiling Point CalculatorFree online calculator with formula and worked example.

Frequently Asked Questions

What is Atmospheric Pressure?

Atmospheric pressure is the pressure of the air around us; it falls with altitude and varies with weather.

What is the barometric formula used here?

The standard atmosphere relation for the lowest layer of the atmosphere, valid up to about 11 km.

Does atmospheric pressure affect gauge readings?

Not a vented gauge sensor. It does affect absolute readings and sealed gauge sensors.

Learn more on the blog

Gauge pressure transmitter: working principle and applications

A practical guide on instrumentationblog.in with more detail on atmospheric pressure and how it is applied on real plants.

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More Pressure Measurement Terms

Pressure termHydrostatic PressureHydrostatic pressure is the pressure created by the weight of a liquid column; it depends only on height…Pressure termPressure HeadPressure head is pressure expressed as the height of a liquid column that would produce it.Pressure termStatic PressureStatic pressure is the pressure of a fluid measured at right angles to the flow, without the effect of…Pressure termUpper Range LimitUpper range limit is the highest value a transmitter sensor can be calibrated to measure.Pressure termTransmitter TurndownTransmitter turndown is how far a transmitter span is reduced from its sensor upper range limit.Pressure termOverpressure LimitOverpressure limit is the highest pressure a sensor can take without damage or loss of its calibration.

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