Multiply MPa by 145.038
One megapascal is 145.038 psi. Multiplying by 145 in your head gets you there with an error under 0.1%. MPa is the SI metric unit used across Europe and ISO standards; psi is the imperial unit common in the US, so this conversion is mostly about reading foreign engineering specs.
Quick reference
| MPa | psi | Where you see it |
|---|---|---|
| 0.2 MPa | 29 psi | Car tyre pressure |
| 1 MPa | 145 psi | — |
| 10 MPa | 1,450 psi | — |
| 20 MPa | 2,901 psi | Standard hydraulics; C20 concrete |
| 35 MPa | 5,076 psi | Heavy hydraulics (excavators) |
| 100 MPa | 14,504 psi | High-pressure metal forming |
1 MPa also equals exactly 10 bar and 1,000 kPa, which is a handy cross-check.
The two mistakes that bite
- MPa is not kPa. 1 MPa = 1,000 kPa. Reading a spec of 20 MPa as 20 kPa is a thousandfold error — the difference between heavy hydraulics and a light breeze.
- Gauge vs absolute. A manometer reads gauge pressure (0 = atmosphere). If a spec means absolute, add about 0.101 MPa (14.7 psi) for the atmosphere before comparing.
Common questions
How many psi are in one MPa?
One MPa is 145.038 psi. For a fast estimate, multiply the MPa figure by 145 — the error is under a tenth of a percent.
How do I convert psi back to MPa?
Divide the psi by 145.038, or multiply by 0.00689. So 100 psi is 100 divided by 145, which is 0.69 MPa.
What is the difference between psi, psig and psia?
Psig is gauge pressure, read relative to the atmosphere, which is what a tyre or hydraulic gauge shows. Psia is absolute pressure, measured from a vacuum. Psia equals psig plus about 14.7. A plain MPa figure is usually absolute unless stated otherwise.
