Pressure is defined as force applied perpendicular to the surface of an object per unit area. In engineering, two of the most common units encountered are the Pound per square inch (psi) and the Megapascal (MPa).
Pound per square inch (psi): A unit of pressure in the Imperial and US Customary systems. It is widely used in North America for tire pressure, hydraulic systems, and industrial gas storage.
Megapascal (MPa): A derived unit of pressure in the International System of Units (SI). One Megapascal is equal to one million Pascals. It is the standard unit for material strength, structural engineering, and high-pressure fluid systems globally.
The conversion factor is derived from the definition of the pound-force and the square inch in SI units. To convert psi to MPa, we use the factor \(1 \text{ psi} \approx 0.006894757 \text{ MPa}\). This relationship is essential for engineers working on international projects where specifications may alternate between imperial and metric standards.
Pound per square inch to Megapascal Conversion Reference Table
Pound per square inch (psi)
Megapascal (MPa)
0.1
6.8948e-04
0.5
0.0034
1.0
0.0069
2.0
0.0138
5.0
0.0345
10.0
0.0689
20.0
0.1379
50.0
0.3447
100.0
0.6895
500.0
3.4474
1000.0
6.8948
Conversion Example: 10 psi to MPa
To convert a pressure value from psi to MPa, multiply the given value by the conversion factor of 0.006894757.
Step 1: Identify the pressure value in psi (10 psi).
This factor is derived from the exact definition of the pound-force (4.4482216152605 newtons) divided by the area of a square inch (0.00064516 square meters). The resulting value is 6894.757 Pascals per psi, which equates to 0.006894757 MPa.
You should use MPa when working with international engineering standards (ISO), material yield strength data, or scientific research. PSI is generally reserved for legacy equipment, automotive applications, and specific regional industrial standards in the United States.
"On fait la science avec des faits, comme on fait une maison avec des pierres ; mais une accumulation de faits n'est pas plus une science qu'un tas de pierres n'est une maison." "Science is built up of facts, as a house is built of stones; but an accumulation of facts is no more a science than a heap of stones is a house." — Henri Poincaré (French Mathematician, Theoretical Physicist & Mining Engineer)