atm to mbar Converter

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Convert atmospheres to millibars using the exact relation 1 atm = 1,013.25 mbar (= 1,013.25 hPa). Anchors: 0.5 atm = 506.63 mbar, 1 atm = 1,013.25 mbar, 2 atm = 2,026.50 mbar, 5 atm = 5,066.25 mbar. Useful for translating chemistry textbook atmospheric pressures into the millibar/hectopascal scale used by meteorology. Browser-local.

Atmosphere (atm)
Millibar (mbar)

Atmosphere (atm) → Millibar (mbar)

Quick reference table

Atmosphere (atm)Millibar (mbar)
0.5 atm506.625 mbar
1 atm1013.25 mbar
1.5 atm1519.875 mbar
2 atm2026.5 mbar
5 atm5066.25 mbar
10 atm10132.5 mbar

Glossary

Atmosphere (atm)

A standard atmosphere is defined as exactly 101,325 Pa (= 1.01325 bar = 760 mmHg = 14.696 psi). It represents average atmospheric pressure at sea level under standard conditions. Used in chemistry (gas-law problems), high-altitude aviation references and pressure-vessel ratings. Not the same as the technical atmosphere (at, ≈ 98,066.5 Pa) — that is a separate, rarely used unit.

Millibar (mbar)

A millibar equals one thousandth of a bar, or 100 Pa. It is identical to the hectopascal (hPa) — meteorologists and weather services use both names interchangeably. Standard atmospheric pressure is 1013.25 mbar (= 1013.25 hPa). Surface weather charts, barometers and aircraft altimeters report station pressure in mbar/hPa.

Metric / SI pressure

In the metric system, pressure is reported in pascals (SI base) or its multiples — kilopascal (kPa, 10³ Pa), megapascal (MPa, 10⁶ Pa) — and the related non-SI unit bar (10⁵ Pa). The millibar/hectopascal (mbar = hPa = 100 Pa) is used in meteorology. All metric units relate by exact powers of ten, so conversions between them are simple shifts of decimal point.

Imperial / US pressure

US engineering and automotive primarily report pressure in pounds per square inch (psi). 1 psi ≈ 6,894.76 Pa, defined as one pound-force per square inch. Standard atmospheric pressure is 14.696 psi. The closely related "psi-gauge" (psi-g) measures pressure above atmospheric, while "psi-absolute" (psi-a) measures total pressure including atmospheric.

Related tools

mbar to atm
Convert mbar to atm — 1013.25 mbar = 1 atm
atm to Bar
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Convert atm to kPa — 1 atm = 101.325 kPa exactly
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