Inches Of Mercury to PSI (inHg to psi)

1 inch of mercury equals 0.4911541475 pounds per square inch (rounded).

1 inch of mercury = 0.4911541475 pounds per square inch

How to convert inches of mercury to pounds per square inch

To convert inches of mercury to pounds per square inch, multiply the number of inches of mercury by 0.4911541475. The factor is rounded to 10 significant digits. To go the other way, multiply pounds per square inch by 2.036020677 (rounded).

pounds per square inch = inches of mercury × 0.4911541475

Example: 10 inches of mercury = 4.911541475 pounds per square inch.

About these units

Inch Of Mercury (inHg)

US & ImperialCurrent unit

About 3,386.39 pascals. US weather reports and aircraft altimeters quote barometric pressure in inches of mercury.

Barometers in the United States still speak in inches. The inch of mercury is the pressure exerted by a 1-inch (25.4 mm) column of mercury under standard gravity, which is a conventional value of about 3,386.389 pascals. Because mercury's density depends on temperature, older literature that used a 60 degrees Fahrenheit basis gives about 3,376.85 pascals instead.

Its modern home is weather and flying. US weather reports quote barometric pressure in inHg, and North America and Japan give altimeter settings in it. Aircraft at higher altitudes set their altimeters to a standard 29.92 inHg, which is where flight levels come from, and that number equals one standard atmosphere.

Mechanics know it from vacuum and boost gauges. Technicians describe refrigerant-system vacuum in inHg, automotive cooling system fill tools typically hold 22 to 27 inHg of vacuum, and railways once used it for vacuum brakes.

1 inch of mercury = 3,386.38864 pascals (approximately).

Sources: Wikipedia: Inch of mercury; Wikipedia: Standard atmosphere (unit); Wikipedia: Atmospheric pressure

Pound Per Square Inch (psi)

US & ImperialCurrent unit

About 6,894.757 pascals. The common unit for tire pressure, hydraulics and gas pipelines in the US.

Unlike most pressure units, psi has no namesake: it simply spells out its own definition, one pound-force acting on one square inch, and it is based on avoirdupois units. Used mainly in the United States, it is about 6.895 kilopascals.

The letters after the unit matter. Psia is measured against a vacuum, while psig is measured against the surrounding air, so at sea level, where the atmosphere is about 14.7 psi, you add that amount to a gauge reading to get an absolute one. A bicycle tire at 65 psig is therefore at 79.7 psia, and the label psid means a difference between two pressures rather than a reference to ambient air.

Typical automobile tires are listed at about 32 psig, and road racing bicycle tires at about 120 psig. One standard atmosphere is 14.696 psi, which gives a feel for how many multiples of sea-level air those tire pressures represent.

1 pound per square inch = 6,894.757293 pascals (approximately).

Sources: Wikipedia: Pounds per square inch; Wikipedia: Standard atmosphere (unit)

Related conversions

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