hPa to atm Converter

How to convert hectopascals to atmospheres

Formulaatm = hPa × 0.0009869232667

Because one standard atmosphere equals 1,013.25 hectopascals, you can also divide: atm = hPa ÷ 1,013.25.

A hectopascal is smaller than a standard atmosphere: it takes 1,013.25 hectopascals to make one standard atmosphere.

Worked examples

1 hectopascal1 hPa × 0.0009869232667 = 0.0009869232667 atm
5 hectopascals5 hPa × 0.0009869232667 = 0.004934616334 atm
10 hectopascals10 hPa × 0.0009869232667 = 0.009869232667 atm
20 hectopascals20 hPa × 0.0009869232667 = 0.01973846533 atm
100 hectopascals100 hPa × 0.0009869232667 = 0.09869232667 atm

Hectopascals to atmospheres conversion table

Values are calculated by the conversion engine and rounded to 8 significant figures.

Hectopascals to atmospheres: 0.1–10 hPa
Hectopascals (hPa)	Atmospheres (atm)
0.1 hPa	0.000098692327 atm
0.25 hPa	0.00024673082 atm
0.5 hPa	0.00049346163 atm
1 hPa	0.00098692327 atm
2 hPa	0.0019738465 atm
3 hPa	0.0029607698 atm
4 hPa	0.0039476931 atm
5 hPa	0.0049346163 atm
6 hPa	0.0059215396 atm
7 hPa	0.0069084629 atm
8 hPa	0.0078953861 atm
9 hPa	0.0088823094 atm
10 hPa	0.0098692327 atm

Hectopascals to atmospheres: 12–1,000 hPa
Hectopascals (hPa)	Atmospheres (atm)
12 hPa	0.011843079 atm
15 hPa	0.014803849 atm
20 hPa	0.019738465 atm
25 hPa	0.024673082 atm
30 hPa	0.029607698 atm
40 hPa	0.039476931 atm
50 hPa	0.049346163 atm
75 hPa	0.074019245 atm
100 hPa	0.098692327 atm
250 hPa	0.24673082 atm
500 hPa	0.49346163 atm
1,000 hPa	0.98692327 atm

About the units

Hectopascal (hPa)

One hundred pascals, numerically equal to a millibar. Weather maps show sea-level pressure in hPa (around 1013). One hectopascal equals 100 pascals (Pa).

Standard atmosphere (atm)

Exactly 101,325 Pa — average sea-level air pressure.

Frequently asked questions

How many atmospheres are in one hectopascal?

There are 0.0009869232667 atmospheres in one hectopascal, and this value is exact by definition.

How do I convert hectopascals to atmospheres?

Multiply the number of hectopascals by 0.0009869232667. For example, 10 hPa × 0.0009869232667 = 0.009869232667 atm.

How many hectopascals are in one standard atmosphere?

One standard atmosphere equals 1,013.25 hectopascals. That is the reverse factor, 1 ÷ 0.0009869232667.

What is 10 hectopascals in atmospheres?

10 hPa = 0.009869232667 atm.

Is this hPa to atm converter accurate?

Yes. Both units are defined exactly in terms of SI units, so the conversion factor is exact; results are shown to 12 significant figures by default and you can change precision in the converter. Calculations run in your browser using the same tested engine that generated this page.