Enter millibars or atmospheres into the calculator to convert to the other value.
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Mbar to Atm Formula
atm = mbar / 1013.25
mbar = atm * 1013.25
- 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 | Near 5,500 m elevation |
| 850 | 0.8389 | Tropical cyclone center |
| 1000 | 0.9869 | Common round figure |
| 1013.25 | 1.0000 | Standard atmosphere |
| 1050 | 1.0363 | Strong high-pressure system |
| 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. This calculator treats input as absolute pressure. If your reading is gauge pressure (pressure above local atmospheric), add the local atmospheric pressure before converting to atm absolute.