Convert Millibar to Pound per Square Inch (mbar → psi)

Converting millibars to psi is straightforward: multiply by the conversion factor. Follow these three steps to do it by hand or in your head.

1. 1
   Take your value in millibars

   Start with the number of millibars (mbar) you want to convert.
2. 2
   Multiply by 0.014504

   The conversion factor from mbar to psi is 0.014504. Multiply your value by this number.
3. 3
   Read the result in psi

   The result is your value in psi (psi).

Multiply the value in millibars by 0.014504. For the reverse direction, multiply by 68.947573.

• ✓1 mbar = 1 hPa = 100 Pa.
• ✓Weather reports: "1013 hPa" and "1013 mbar" mean the same thing.
• ✓Hurricane strength correlates with central pressure drop.

• ✗Confusing mbar and bar — 1000× difference.
• ✗Using mbar for industrial pressures — too small.
• ✗Mixing hPa and mbar in casual writing without noting they are equal.

What is the Millibar?

The millibar equals exactly 100 pascals and is the legacy meteorology unit, identical to the modern hectopascal (hPa). Most weather services worldwide transitioned from millibars to hectopascals in the late 20th century, but the unit persists in aviation weather reports, marine forecasts, and older barometric instruments. Standard sea-level atmospheric pressure is 1,013.25 mbar (or hPa). Hurricane and typhoon central pressures are reported in millibars: a major Category 5 hurricane like Hurricane Andrew (1992) had a central pressure of about 922 mbar. The millibar relates to the hectopascal (1 mbar = 1 hPa exactly), the bar (1,000 mbar = 1 bar), the pascal (100 Pa = 1 mbar), and the atmosphere (1,013.25 mbar = 1 atm). Despite the official preference for hPa, the millibar is retained in some traditional contexts and older texts.

• Weather reports and atmospheric pressure
• Altimetry and aviation
• Historical weather records

What is the Pound per Square Inch?

Pounds per square inch (psi) equals approximately 6,895 pascals and is the standard pressure unit in American tire pressures, hydraulics, and gas-cylinder specifications. American car tires are typically inflated to 30–35 psi, household water systems run at 40–60 psi, and scuba tanks are filled to 3,000 psi (about 200 bar). The psi is essential in American engineering for stress calculations, hydraulic systems, and pneumatic equipment. Two variants exist: 'psig' (gauge, measured above atmospheric) and 'psia' (absolute, including atmosphere) — gauge is the default unless specified. The psi relates to the pascal (1 psi ≈ 6,895 Pa), the kilopascal (1 psi ≈ 6.895 kPa), the bar (14.504 psi = 1 bar), the atmosphere (14.696 psi = 1 atm), and the inch of mercury (1 inHg ≈ 0.491 psi). Outside the US, kPa or bar dominate.

• US tyre pressures
• US plumbing and water system specs
• US compressed-air tool ratings