From time to time, it will be necessary for engineers working on all manner of projects to convert between units of pressure such as PSI (pounds per square inch), Bar, and Pascal.
After all, engineering projects frequently involve equipment, standards, or teams from different parts of the world where the exact units customarily used may vary.
PSI, for instance, sees widespread use in the United States, particularly in automotive and industrial contexts. In metric-based regions, meanwhile, Pascal and Bar are typically used.
Plus, of course, engineering depends hugely on precision, and pressure is a critically important parameter across such applications as hydraulics, pneumatics, and structural engineering.
In the event, then, that you mistake one unit of pressure for another (for example, PSI for Bar), you could be risking dire consequences, such as over-pressurised systems, outright equipment failure, or major safety hazards.
A Quick Introduction To PSI, Bar, And Pascal
Before we go any further, here is a summary of these three commonly used pressure units:
- PSI, or pounds per square inch, is an imperial unit of pressure. Specifically, it measures the amount of force applied over an area of one square inch.
- Bar is a metric unit of pressure. One Bar is defined as 100,000 Pascals (100 kilopascals) and is approximately equivalent to the atmospheric pressure at sea level. Unlike the Pascal, though, Bar is not part of the International System of Units (SI).
- Pascal is another metric unit of pressure – specifically, the SI unit. Named in honour of the French mathematician and physicist Blaise Pascal (1623-1662), the Pascal is defined as one newton per square metre.
What Are the Key Conversion Factors for These Pressure Units?
Here’s your “cut out and keep” guide of how these different units are equivalent to each other:
- 1 PSI ≈ 0.0689476 Bar ≈ 6,894.76 Pascal (Pa)
- 1 Bar = 100,000 Pascal (Pa) ≈ 14.5038 PSI
- 1 Pascal (Pa) = 0.00001 Bar ≈ 0.000145038 PSI
To put those relationships another way:
- To convert from PSI to Bar, multiply by 0.0689476
- To convert from Bar to PSI, multiply by 14.5038
- To convert from PSI to Pascal, multiply by 6,894.76
- To convert from Pascal to PSI, multiply by 0.000145038
- To convert from Bar to Pascal, multiply by 100,000
- To convert from Pascal to Bar, multiply by 0.00001
So, to give a few quick examples, if you needed to convert 50 PSI to Bar, the relevant calculation would be 50 x 0.0689476 = 3.44738 Bar. Or if you were looking to figure out how much 2 Bar is in PSI, you would need to use the formula 2 x 14.5038 = 29.0076 PSI.
Other Things to Bear in Mind When Converting Between These Pressure Units
It is important not to round your numbers too early when undertaking calculations like these, as doing so could skew the results. Ensuring unit consistency is crucial, too; for example, you shouldn’t be mixing megapascals (MPa) or kilopascals (kPa) unless you adjust the conversion factor in accordance with this.
Finally, you might be wondering: why not just use an online calculator for these conversions, to help save time and hassle? You may have noticed, for instance, that the website of electrical component supplier RS offers an excellent pressure unit conversion calculator for engineers.
Our short answer to this question is: yes, a reputable online calculator or converter can certainly bring the above benefits, in addition to better ensuring accuracy.
Still, even the use of a calculator can bring a risk of human error (such as if you accidentally input the wrong numbers into the tool). So, it is a good idea to get to grips with manual conversion calculations too, given that the use of both methods will help you verify the accuracy of the other one. That, in turn, will be good news for your broader project.
