Convert pressure between mbar or hPa and atm in both directions, with equivalents in Pa, kPa, bar, Torr, and psi, plus a pressure-reference note.
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mbar to atm Formula
- atm = pressure in standard atmospheres
- mbar = pressure in millibars (1 mbar = 100 Pa)
- 1013.25 = millibars in one standard atmosphere
1 hPa equals 1 mbar, so the same conversion applies. One standard atmosphere is defined as exactly 101,325 Pa, which fixes the 1013.25 mbar constant. This is a unit conversion only and does not depend on temperature or gas type.
Reference Values and Common Conversions
Use these tables to sanity-check a result or look up common values without retyping.
| mbar | atm | Context |
|---|---|---|
| 1 | 0.000987 | Rough vacuum |
| 500 | 0.4934 | 0.4934 of a standard atmosphere |
| 850 | 0.8389 | 0.8389 of a standard atmosphere |
| 1000 | 0.9869 | Common round figure |
| 1013.25 | 1.0000 | Standard atmosphere |
| 1050 | 1.0363 | 1.0363 of a standard atmosphere |
| 2000 | 1.9738 | Roughly 2 atm absolute |
| atm | mbar | kPa | psi |
|---|---|---|---|
| 0.5 | 506.63 | 50.66 | 7.35 |
| 1 | 1013.25 | 101.33 | 14.70 |
| 2 | 2026.5 | 202.65 | 29.39 |
| 5 | 5066.25 | 506.63 | 73.48 |
| 10 | 10132.5 | 1013.25 | 146.96 |
Worked Examples and FAQ
Example 1. Convert 980 mbar to atm: 980 / 1013.25 ≈ 0.9672 atm.
Example 2. Convert 1.25 atm to mbar: 1.25 × 1013.25 ≈ 1266.56 mbar.
Is hPa the same as mbar? Yes. 1 hPa = 100 Pa = 1 mbar. Weather services often report hPa, but the number is identical to mbar.
Why 1013.25 and not 1000? The standard atmosphere is defined as 101,325 Pa exactly. Dividing by 100 Pa per mbar gives 1013.25 mbar.
Does temperature affect this conversion? No. Both units measure pressure directly. Temperature only matters if you are converting between pressure and another quantity such as density or moles of gas.
Gauge vs absolute pressure. Unit conversion preserves the input pressure reference. If your reading is gauge pressure and you need absolute pressure, first add the local atmospheric pressure in the same units. Negative readings can represent gauge or differential pressure, but cannot represent absolute pressure.
