Millibars to Atmospheres
A millibar is one thousandth of a bar, the standard unit meteorologists use for barometric pressure readings. One atmosphere is the average air pressure at sea level, used as a reference unit in chemistry and physics. 1 mbar equals ≈0.000986923 atm, so converting between them is a matter of multiplying by that fixed factor — type any value into the converter below and both sides update instantly as you type.
Both units belong to pressure, measured here against pressure's base unit (Pa) — every other pressure unit on this site converts through that same reference point, which is why the table below can also be read as a quick cross-check against nearby values.
Formula
atm = mbar × ≈0.000986923
mbar = atm × 1,013.25
Worked example: 5 mbar × ≈0.000986923 = ≈0.00493462 atm.
Conversion table
| Millibar (mbar) | Atmosphere (atm) |
|---|---|
| 1 mbar | ≈0.000986923 atm |
| 2 mbar | ≈0.00197385 atm |
| 3 mbar | ≈0.00296077 atm |
| 5 mbar | ≈0.00493462 atm |
| 10 mbar | ≈0.00986923 atm |
| 20 mbar | ≈0.0197385 atm |
| 25 mbar | ≈0.0246731 atm |
| 50 mbar | ≈0.0493462 atm |
| 100 mbar | ≈0.0986923 atm |
| 250 mbar | ≈0.246731 atm |
| 500 mbar | ≈0.493462 atm |
| 1,000 mbar | ≈0.986923 atm |
Frequently asked
- How many Atmospheres in a millibar?
- 1 mbar equals ≈0.000986923 atm.
- How do I convert Millibars to Atmospheres?
- Multiply the value in mbar by ≈0.000986923 to get atm. The converter above does this instantly as you type.
- Is the conversion exact?
- Yes — Millibar and Atmosphere are both defined by a fixed conversion factor to pressure's base unit (Pa), so the result shown is exact to the precision displayed, not an approximation.