Megapascals to psi:
multiply by 145.04

How many psi are in a megapascal?

One megapascal is 145.0377377 psi. The megapascal is the SI unit used for strength and high pressures, while psi is the customary unit in the United States. The two appear side by side in materials and engineering data.

A megapascal is one million pascals, or one newton per square millimetre. That link explains why stress and strength values for steel, concrete and plastics are given in MPa.

The MPa to psi formula

A second example runs in reverse. A US pressure rating of 5,000 psi on a hydraulic hose is 5,000 × 0.006894757293 = 34.47379 MPa, which is about 34.5 MPa.

Chart: MPa to psi

To use the chart for other values, combine rows. A 35 MPa figure is 25 MPa plus 10 MPa, so 3,625.943443 + 1,450.377377 = 5,076.32082 psi.

Where MPa to psi is used

• Concrete: strength grades such as 25 MPa or 32 MPa are often compared with US figures in psi.
• Steel and aluminium: yield and tensile strength tables use MPa, while older US data uses psi or ksi, where 1 ksi is 1,000 psi.
• Hydraulics: pressure ratings on pumps, rams and hoses are given in MPa in many countries.
• Pressure washers and industrial pumps: ratings may be listed in either unit.

A materials example: choosing a pipe or concrete grade

Imagine you are reading a data sheet for a plastic pipe that is rated for 1.6 MPa of working pressure, and the pump supplier quotes the pump in psi. Converting 1.6 MPa gives 1.6 × 145.0377377 = 232.0604 psi, so a pump that delivers 250 psi would exceed the pipe rating, even though 250 looks close to 232.

The same method helps with concrete. A mix specified as 32 MPa needs to be compared with a supplier who quotes 4,500 psi. Since 32 MPa is 32 × 145.0377377 = 4,641.208 psi, the 4,500 psi mix is slightly weaker than the specification, which is worth catching before the pour.

• Convert the rating first, then compare the two numbers in the same unit.
• Keep at least four significant figures until the final comparison.
• Never round up a rating in your favour. Round down when you check a safe working limit.

Check your answer in two steps

Start with a rough figure, then compare. For 12 MPa, multiply by 145 to get about 1,740 psi, and the exact answer is 1,740.453 psi. If your calculator shows a number near 17 or 174,000, the decimal has slipped. Doing this check takes five seconds and catches most mistakes before they reach a drawing or an order.

Common mistakes with MPa and psi

• Mixing up MPa and kPa. One MPa is 1,000 kPa, so using the kPa factor gives an answer 1,000 times too small.
• Confusing psi with ksi. A tensile strength of 60 ksi is 60,000 psi, which is about 413.7 MPa.
• Reading MPa as GPa. Modulus of elasticity for steel is given in GPa, not MPa, which is a thousand times larger.
• Rounding 145.04 to 150. That is a 3.4 percent error, which can matter when checking a safety margin.