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Pressure

hPatoatm

Convert hectopascals (hPa) to standard atmospheres (atm).

Factor1 hPa = 0.0009869233 atm

Converter

hPa

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

Result
1atm

Rendered to 6 significant figures.

Formula

Formula
atm = hPa × 0.0009869233

Multiply any value in hectopascals by 0.0009869233 to obtain the value in standard atmospheres.

Worked example

Convert 1013.25 hPa to atm.

  1. 01Start with 1013.25 hPa.
  2. 02Multiply by the conversion factor: 1013.25 × 0.0009869233 = 1 atm.
Result1013.25 hPa = 1 atm

Conversion table

hPaatm
10.00098692
20.0019738
50.0049346
100.0098692
200.019738
500.049346
1000.098692
2000.19738
5000.49346
10000.98692

Reference values rounded to 5 significant figures for display.

FAQ

What is the conversion factor from hPa to atm?
1 hPa equals 0.0009869233 atm. To convert, multiply the value in hectopascals by 0.0009869233.
How do I convert 1 hPa to atm?
1 hPa = 0.000986923 atm. For any value, multiply by 0.0009869233.
How do I convert atm back to hPa?
Divide by the same factor — or equivalently, multiply by 1013.25. So 1 atm = 1013.25 hPa.
When would I need to convert hectopascal to standard atmosphere?
Pressure conversions between hPa and atm are common when working with mixed-vendor instrumentation, when piping codes use different units to process datasheets, or when converting field readings into SI for hydraulic calculations.
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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