What is the correct formula for converting barometric pressure to PSIA?

To convert barometric pressure from inches of mercury ("Hg) to pounds per square inch absolute (PSIA), the correct formula involves using a specific conversion factor. Atmospheric pressure at sea level is approximately 29.92 inches of mercury, and this value corresponds to 14.7 PSIA. Therefore, the conversion is based on the factor that 1 inch of mercury equals approximately 0.491 PSI at sea level.

Using this conversion factor, when you multiply the height of mercury in inches (in "Hg) by 0.491, you accurately convert the pressure to PSI. This is why the formula that includes this multiplication factor is the correct choice for converting barometric pressure to PSIA.

In contrast, other options either provide incorrect multiplication factors, suggest adding or subtracting values that are not applicable for direct conversions, or misrepresent the relationship between units of pressure. The key is to remember the direct conversion relationship, making the use of 0.491 as the multiplier essential for accurate calculations.