The psi to atm conversion is an important unit conversion for scientists and engineers. Both psi and atm are units of pressure, which is force per unit area. PSI stands for pounds per square inch (lb/in2), or more properly, pound force per square inch. Meanwhile atm is the abbreviation for atmosphere, where one atmosphere is approximately the Earth’s atmospheric pressure at sea level. It’s easy to convert psi to atm. Here is the formula, along with worked example problems.
psi to atm Formula
The formula for converting psi to atm is:
atm = psi ÷ 14.696
or
atm = psi ÷ 14.7
Which formula you use depends on how many significant digits you’re carrying in your calculations.
psi to atm Example Problem
For example, convert 65 psi to atm:
atm = (psi) ÷ (14.7 atm/psi) = 65 ÷ 14.7 = 4.4
65 psi equals 4.4 atm.
Note how the “psi” units cancel out in the numerator and denominator. If you set up the pressure conversion incorrectly, the unit won’t cancel out. Also, not that the same pressure in atmosphere is a smaller number than the pressure in pounds per square inch. These are two easy way of checking your work.
Let’s try another example. Convert 30 psi to atm.
atm = psi ÷14.7 = 30 ÷14.7 = 2.0 atm
So, 14.7 psi is about 2 atmospheres.
atm to psi Conversion
It’s equally easy converting atmospheres to pounds per square inch or atm to psi. Use the conversion factor:
psi = atm x 14.696
For example, convert 50 atm to psi:
psi = atm x 14.696 = 50 x 14.696 = 734.8
So, a pressure of 50 atmosphere is 734.8 psi. Once again, check you work. Expect a value in pounds per square inch to be more than 10x bigger than its equivalent value in atmospheres.
References
- Atkins, P.; de Paula, J. (2006). Elements of Physical Chemistry (4th ed.). W. H. Freeman. ISBN 0-7167-7329-5.
- Finnemore, John, E.; Franzini, Joseph B. (2002). Fluid Mechanics: With Engineering Applications. New York: McGraw Hill, Inc. ISBN 978-0-07-243202-2.
- Knight, Randall D. (2007). Physics for Scientists and Engineers: A Strategic Approach (2nd ed.). San Francisco: Pearson Addison Wesley. ISBN 978-0-321-51671-8.
- National Institute of Standards and Technology (2008). NIST Special Publication 811 – Guide for the Use of the International System of Units (SI).
- Resnick, Robert; Halliday, David (1960). Physics for Students of Science and Engineering. New York: Wiley.