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Vacuum

atmtombar

Convert standard atmospheres (vacuum) (atm) to millibars (vacuum) (mbar).

Factor1 atm = 1013.25 mbar

Converter

atm

Accepts numbers or expressions, e.g. 150 + 14.7

Result
1013.25mbar

Rendered to 6 significant figures.

Formula

Formula
mbar = atm × 1013.25

Multiply any value in standard atmospheres (vacuum) by 1013.25 to obtain the value in millibars (vacuum).

Worked example

Convert 1 atm to mbar.

  1. 01Start with 1 atm.
  2. 02Multiply by the conversion factor: 1 × 1013.25 = 1013.25 mbar.
Result1 atm = 1013.25 mbar

Conversion table

atmmbar
11013.3
22026.5
55066.3
1010133
2020265
5050663
1001.0133e+5
2002.0265e+5
5005.0663e+5
10001.0133e+6

Reference values rounded to 5 significant figures for display.

FAQ

What is the conversion factor from atm to mbar?
1 atm equals 1013.25 mbar. To convert, multiply the value in standard atmospheres (vacuum) by 1013.25.
How do I convert 1 atm to mbar?
1 atm = 1013.25 mbar. For any value, multiply by 1013.25.
How do I convert mbar back to atm?
Divide by the same factor — or equivalently, multiply by 0.0009869233. So 1 mbar = 0.000986923 atm.
When would I need to convert standard atmosphere (vacuum) to millibar (vacuum)?
Vacuum-pressure conversions between atm and mbar are common in vacuum-chamber instrumentation, pump-down endpoint specification, semiconductor and deposition process work, freeze-drying, electron-microscopy column pressure, vacuum metallurgy and HVAC / refrigeration service. Torr, mmHg and inHg dominate manometric vacuum gauges; mbar is standard on European instruments; micron Hg and mTorr cover high-vacuum work; Pa and kPa are the SI references. This category is vacuum / instrumentation intent — dimensionally the same as pressure, but kept separate so process-pressure searches and vacuum searches stay on the right page.
Is the conversion exact?
The factor shown is precise to at least 7 significant figures. For most process-engineering work this is far better than instrument accuracy. For metrology or trade applications, refer to the relevant national standard (NIST, BIPM, ISO 80000).

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