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Barometric Pressure Conversion

Convert weather station and aviation barometric pressures across common units.

Formula shown0 inputs definedUpdated Nov 2025By CalcuTotal TeamFree, no sign-up

Quick Summary

Use this when you need:

Convert a home weather station output in inHg into hPa for WMO-style logs
Check aviation altimeter settings that swap between inHg and hPa
Calibrate barometric sensors by comparing Pa, kPa, and mmHg readings side by side

You’ll get:Pressure

How this is calculated

Formula:

pressure_target = pressure_source

In plain language:

Barometric readings are normalized to Pascals, then expressed in meteorological units such as hPa, inHg, or mmHg; sea-level standard pressure is 1013.25 hPa (29.92 inHg).

The formula is always visible so you can verify the math and explain your numbers to anyone who asks.

What these terms mean

Pressure

Pressure used in the calculation.

When to use this calculator

Convert a home weather station output in inHg into hPa for WMO-style logs
Check aviation altimeter settings that swap between inHg and hPa
Calibrate barometric sensors by comparing Pa, kPa, and mmHg readings side by side

Last updated: November 21, 2025

Barometric pressure converter explained

Weather stations, aviation briefings, and lab logs switch between inches of mercury, hectopascals, millibars, and atmospheres. This converter keeps those readings consistent so you can compare altimeter settings, storm reports, or sensor calibrations without error.

How the conversion works

The tool normalizes every reading to Pascals (Pa), then rescales to the chosen unit. Anchors:

1\,\text{atm} = 101{,}325\,\text{Pa}, \quad 1\,\text{inHg} \approx 3{,}386.389\,\text{Pa}, \quad 1\,\text{mmHg} \approx 133.322\,\text{Pa}

Standard sea-level pressure is $1013.25\,\text{hPa} = 29.92\,\text{inHg}$ , a helpful sense-check when comparing readings.

Units and conversions

Unit	Symbol	Relation to Pa
Hectopascal	hPa	$1\,\text{hPa} = 100\,\text{Pa}$
Millibar	mbar	$1\,\text{mbar} = 100\,\text{Pa}$
Kilopascal	kPa	$1\,\text{kPa} = 1{,}000\,\text{Pa}$
Pascal	Pa	base unit
Inch of mercury	inHg	$1\,\text{inHg} \approx 3{,}386.389\,\text{Pa}$
Millimetre of mercury	mmHg	$1\,\text{mmHg} \approx 133.322\,\text{Pa}$
Atmosphere	atm	$1\,\text{atm} = 101{,}325\,\text{Pa}$
Bar	bar	$1\,\text{bar} = 100{,}000\,\text{Pa}$

Worked examples

Aviation altimeter setting in inHg → hPa
Given $30.12\,\text{inHg}$ :
$P_{\text{hPa}} = 30.12 \times \frac{3{,}386.389}{100} \approx 1{,}021.0\,\text{hPa}$
Result: 1,021.0 hPa.
Weather station reading in hPa → inHg
Given $1{,}018\,\text{hPa}$ :
$P_{\text{inHg}} = 1{,}018 \times \frac{100}{3{,}386.389} \approx 30.06\,\text{inHg}$
Result: 30.06 inHg.

Tips and pitfalls

hPa and mbar are numerically identical; use whichever your audience expects.
Verify whether your sensor outputs station pressure or sea-level corrected pressure before comparing to forecasts.
For high-altitude sites, expect lower station pressure; do not “correct” it twice.
Keep at least two decimal places in inHg for aviation; small deltas affect altitude calculations.

References and further reading

Frequently Asked Questions

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Calculator info

Version:: v1.0.0
Last reviewed:: Nov 21, 2025
Sensitivity:: low
References:: 2

Last updated: November 21, 2025

Barometric pressure converter explained

How the conversion works

The tool normalizes every reading to Pascals (Pa), then rescales to the chosen unit. Anchors:

1\,\text{atm} = 101{,}325\,\text{Pa}, \quad 1\,\text{inHg} \approx 3{,}386.389\,\text{Pa}, \quad 1\,\text{mmHg} \approx 133.322\,\text{Pa}

Standard sea-level pressure is $1013.25\,\text{hPa} = 29.92\,\text{inHg}$ , a helpful sense-check when comparing readings.

Units and conversions

Unit	Symbol	Relation to Pa
Hectopascal	hPa	$1\,\text{hPa} = 100\,\text{Pa}$
Millibar	mbar	$1\,\text{mbar} = 100\,\text{Pa}$
Kilopascal	kPa	$1\,\text{kPa} = 1{,}000\,\text{Pa}$
Pascal	Pa	base unit
Inch of mercury	inHg	$1\,\text{inHg} \approx 3{,}386.389\,\text{Pa}$
Millimetre of mercury	mmHg	$1\,\text{mmHg} \approx 133.322\,\text{Pa}$
Atmosphere	atm	$1\,\text{atm} = 101{,}325\,\text{Pa}$
Bar	bar	$1\,\text{bar} = 100{,}000\,\text{Pa}$

Worked examples

Aviation altimeter setting in inHg → hPa
Given $30.12\,\text{inHg}$ :
$P_{\text{hPa}} = 30.12 \times \frac{3{,}386.389}{100} \approx 1{,}021.0\,\text{hPa}$
Result: 1,021.0 hPa.
Weather station reading in hPa → inHg
Given $1{,}018\,\text{hPa}$ :
$P_{\text{inHg}} = 1{,}018 \times \frac{100}{3{,}386.389} \approx 30.06\,\text{inHg}$
Result: 30.06 inHg.

Tips and pitfalls

hPa and mbar are numerically identical; use whichever your audience expects.
Verify whether your sensor outputs station pressure or sea-level corrected pressure before comparing to forecasts.
For high-altitude sites, expect lower station pressure; do not “correct” it twice.
Keep at least two decimal places in inHg for aviation; small deltas affect altitude calculations.

Quick Summary

Calculator Tool

How this is calculated

What these terms mean

Pressure

When to use this calculator

Barometric pressure converter explained

How the conversion works

Units and conversions

Worked examples

Tips and pitfalls

References and further reading

Frequently Asked Questions

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Found an error?

Calculator info

Barometric pressure converter explained

How the conversion works

Units and conversions

Worked examples

Tips and pitfalls

References and further reading

Frequently Asked Questions

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atm to Pascals Conversion

Bar To Atm Conversion

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Calculator info