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ATM Conversion

Convert pressure values expressed in atmospheres into other engineering and weather units.

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

Quick Summary

Use this when you need:

Compare lab vacuum readings in torr against equipment specs given in atm or kPa
Translate weather station data from hPa or inHg into atmospheres for reports
Convert scuba or compressor pressures expressed in psi into atm for safety checks

You’ll get:Pressure

How this is calculated

Formula:

pressure_target = pressure_source

In plain language:

Pressures are normalized to Pascals (Pa) using 1 atm = 101,325 Pa and scaled into the target unit, handling both absolute and barometric conventions.

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

Compare lab vacuum readings in torr against equipment specs given in atm or kPa
Translate weather station data from hPa or inHg into atmospheres for reports
Convert scuba or compressor pressures expressed in psi into atm for safety checks

Last updated: November 21, 2025

ATM conversion explained

Process specs, weather reports, and vacuum gauges bounce between atmospheres, kilopascals, bar, and psi. This converter keeps them aligned so you can compare lab data, compressor ratings, and altimeter settings without mental math.

How the conversion works

Standard atmosphere is defined as $1\,\text{atm} = 101{,}325\,\text{Pa}$ . Conversions scale linearly from that base:

P_{\text{target}} = P_{\text{atm}} \times \frac{101{,}325\,\text{Pa}}{1\,\text{atm}} \times \frac{1}{f_{\text{target}}}

where $f_{\text{target}}$ is the Pa-per-unit factor (e.g., $100{,}000$ for bar, $6{,}894.757$ for psi).

Units and conversions

Unit	Symbol	Relation to Pa
Atmosphere	atm	$1\,\text{atm} = 101{,}325\,\text{Pa}$
Bar	bar	$1\,\text{bar} = 100{,}000\,\text{Pa}$
Kilopascal	kPa	$1\,\text{kPa} = 1{,}000\,\text{Pa}$
Pascal	Pa	base unit
Megapascal	MPa	$1\,\text{MPa} = 1{,}000{,}000\,\text{Pa}$
Pound per square inch	psi	$1\,\text{psi} = 6{,}894.757\,\text{Pa}$
Inch of mercury	inHg	$1\,\text{inHg} \approx 3{,}386.389\,\text{Pa}$
Millimetre of mercury	mmHg	$1\,\text{mmHg} \approx 133.322\,\text{Pa}$
Torr	torr	$1\,\text{torr} = 133.322\,\text{Pa}$
Hectopascal	hPa	$1\,\text{hPa} = 100\,\text{Pa}$
Millibar	mbar	$1\,\text{mbar} = 100\,\text{Pa}$

Worked examples

Vacuum level in atm to psi
Given $0.80\,\text{atm}$ :
$P_{\text{psi}} = 0.80 \times \frac{101{,}325}{6{,}894.757} \approx 11.76\,\text{psi}$
Result: 11.8 psi absolute.
Gauge spec in kPa to atm
Given $250\,\text{kPa}$ :
$P_{\text{atm}} = \frac{250{,}000}{101{,}325} \approx 2.47\,\text{atm}$
Result: 2.47 atm.

Tips and pitfalls

Check whether your reading is absolute (psia, bara) or gauge (psig, barg). Gauge adds local atmospheric pressure back in.
Aviation and meteorology often use hPa or inHg; process plants lean on bar or kPa. Pick the right preset card before sharing numbers.
For vacuum work below 0.1 atm, prefer torr or mmHg to keep values intuitive.
Keep at least three significant figures when converting safety limits to avoid rounding under setpoints.

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:: 1

Last updated: November 21, 2025

ATM conversion explained

How the conversion works

Standard atmosphere is defined as $1\,\text{atm} = 101{,}325\,\text{Pa}$ . Conversions scale linearly from that base:

P_{\text{target}} = P_{\text{atm}} \times \frac{101{,}325\,\text{Pa}}{1\,\text{atm}} \times \frac{1}{f_{\text{target}}}

where $f_{\text{target}}$ is the Pa-per-unit factor (e.g., $100{,}000$ for bar, $6{,}894.757$ for psi).

Units and conversions

Unit	Symbol	Relation to Pa
Atmosphere	atm	$1\,\text{atm} = 101{,}325\,\text{Pa}$
Bar	bar	$1\,\text{bar} = 100{,}000\,\text{Pa}$
Kilopascal	kPa	$1\,\text{kPa} = 1{,}000\,\text{Pa}$
Pascal	Pa	base unit
Megapascal	MPa	$1\,\text{MPa} = 1{,}000{,}000\,\text{Pa}$
Pound per square inch	psi	$1\,\text{psi} = 6{,}894.757\,\text{Pa}$
Inch of mercury	inHg	$1\,\text{inHg} \approx 3{,}386.389\,\text{Pa}$
Millimetre of mercury	mmHg	$1\,\text{mmHg} \approx 133.322\,\text{Pa}$
Torr	torr	$1\,\text{torr} = 133.322\,\text{Pa}$
Hectopascal	hPa	$1\,\text{hPa} = 100\,\text{Pa}$
Millibar	mbar	$1\,\text{mbar} = 100\,\text{Pa}$

Worked examples

Vacuum level in atm to psi
Given $0.80\,\text{atm}$ :
$P_{\text{psi}} = 0.80 \times \frac{101{,}325}{6{,}894.757} \approx 11.76\,\text{psi}$
Result: 11.8 psi absolute.
Gauge spec in kPa to atm
Given $250\,\text{kPa}$ :
$P_{\text{atm}} = \frac{250{,}000}{101{,}325} \approx 2.47\,\text{atm}$
Result: 2.47 atm.

Tips and pitfalls

Check whether your reading is absolute (psia, bara) or gauge (psig, barg). Gauge adds local atmospheric pressure back in.
Aviation and meteorology often use hPa or inHg; process plants lean on bar or kPa. Pick the right preset card before sharing numbers.
For vacuum work below 0.1 atm, prefer torr or mmHg to keep values intuitive.
Keep at least three significant figures when converting safety limits to avoid rounding under setpoints.

Quick Summary

Calculator Tool

How this is calculated

What these terms mean

Pressure

When to use this calculator

ATM conversion explained

How the conversion works

Units and conversions

Worked examples

Tips and pitfalls

References and further reading

Frequently Asked Questions

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Bar To Atm Conversion

Barometric Pressure Conversion

bar to psi Conversion

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Calculator info

ATM conversion explained

How the conversion works

Units and conversions

Worked examples

Tips and pitfalls

References and further reading

Frequently Asked Questions

Related Calculators

atm to Pascals Conversion

Bar To Atm Conversion

Barometric Pressure Conversion

bar to psi Conversion

Bar to PSIG Converter

Pressure Converter

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