Article — MPa to PSI Conversion Calculator
MPa to psi Conversion: From SI Pressure to Imperial PSI
One megapascal equals 145.038 pounds per square inch. The reverse is 1 psi = 0.006895 MPa. Both factors derive from the NIST definition of one pound-force per square inch as exactly 6,894.757 Pa, which in turn rests on the international pound (0.45359237 kg) and inch (0.0254 m) treaty values.
MPa is the working unit for high-pressure engineering. Industrial hydraulics run at 20 to 100 MPa, structural concrete is rated by its compressive strength in MPa, and steel yield strengths fall between 250 and 1,500 MPa. The same numbers in psi are 2,900 to 14,500 for hydraulics, 2,900 to 11,000 for concrete, and 36,000 to 220,000 for steel. The two systems show up on the same engineering drawing routinely, especially in industries that source globally.
The MPa to psi conversion factor
The exact factor is 1 MPa = 145.03773773 psi. NIST publishes this value in Special Publication 811. The reciprocal is 1 psi = 0.00689475729 MPa. Both are exact under SI definitions, not measurements, because the pound and inch are fixed by international treaty.
The pascal is the SI unit of pressure: one newton of force per square metre. The megapascal is one million pascals, the practical scale for material strengths and high-pressure systems. Atmospheric pressure expressed in MPa is a small number (0.101 MPa), because the unit is calibrated for industrial rather than meteorological work.
The pascal was named for the seventeenth-century French mathematician Blaise Pascal, whose Treatise on the Equilibrium of Liquids (written around 1653, published posthumously in 1663) laid out the principle that pressure applied to a confined fluid transmits equally in all directions. Every hydraulic press in modern industry is a working demonstration of Pascal's principle.
MPa to psi in hydraulics
Industrial hydraulic systems work at pressures between 20 and 100 MPa (2,900 to 14,500 psi). The standard ranges fall into bands: 2 to 5 MPa for low-pressure applications, 20 to 35 MPa for general industrial hydraulics, 50 to 100 MPa for metal-forming presses, and above 200 MPa for ultra-high-precision applications like waterjet cutting and military hydraulics.
European manufacturers spec hydraulic pressures in MPa or bar; US shops still use psi. The conversion between the two appears on every spec sheet that crosses the Atlantic. A 35 MPa pump rated by a German manufacturer reads as 5,076 psi on a US gauge, and 35 MPa is the most common pressure for construction-equipment hydraulic systems.
- Low-pressure 2–5 MPa (290–725 psi)
- Standard industrial 20–35 MPa (2,900–5,076 psi)
- Construction equipment 30–40 MPa (4,351–5,800 psi)
- Metal-forming press 50–100 MPa (7,250–14,500 psi)
- Waterjet cutting 250–400 MPa (36,000–58,000 psi)
- Military hydraulics 400+ MPa (58,000+ psi)
- Diesel injection pump 200 MPa (29,000 psi)
- Common rail diesel injector up to 250 MPa
Concrete strength in MPa and psi
Structural concrete is rated by its compressive strength in MPa. The European C-grade system writes the strength directly into the name: C20 is 20 MPa, C30 is 30 MPa, C50 is 50 MPa. The American system writes the same strength in psi, so a C30 concrete is also called a 4,000 psi mix (technically 4,351 psi, rounded down for nominal labelling).
Residential foundations typically use C20 or C25 (3,000 to 3,600 psi). Commercial buildings use C30 to C40 (4,400 to 5,800 psi). High-rise structural cores and bridge supports use C50 to C80 (7,250 to 11,600 psi). Specialty concretes for nuclear containment or military applications exceed 100 MPa (14,500 psi).
Steel and material yield strengths
Steel yield strengths are quoted in MPa worldwide for engineering work, with the psi equivalent following in parentheses on US drawings. Mild structural steel (ASTM A36) has a yield strength of 250 MPa, equal to 36,259 psi. High-strength low-alloy steels run 345 to 690 MPa (50,000 to 100,000 psi). Quenched and tempered alloy steels for high-strength bolts reach 1,035 MPa (150,000 psi). Ultra-high-strength martensitic steels for aerospace exceed 2,000 MPa.
The MPa-to-psi conversion is essential when reading material certifications from non-US mills. A test certificate from a Korean or German steel producer will quote yield strength in MPa; the US specifier needs the psi equivalent to verify against the design drawing. A factor-of-145 multiplication brings the numbers into the same system.
MPa and kPa differ by a factor of 1,000. A specification calling for 20 MPa hydraulic pressure (2,901 psi) is not the same as 20 kPa (2.9 psi). Reading one as the other puts a hydraulic system a thousand times under or over pressure. Always check the prefix letter before converting.
MPa, kPa, and bar all on one chart
The metric pressure units form a ladder: 1 MPa = 10 bar = 1,000 kPa = 1,000,000 Pa. Each step changes by a power of ten and the conversion to psi follows along: 1 MPa = 145.038 psi, 1 bar = 14.504 psi, 1 kPa = 0.145 psi.
Pressure ranges in engineering: meteorology and weather use hPa (hectopascals, identical to mbar) at the 1,000 hPa scale; tire pressure and refrigeration use kPa at the 100–1,000 kPa scale; hydraulics and materials use MPa at the 1–1,000 MPa scale. The unit choice is a clue to the application.
Mental math for MPa to psi
Multiply MPa by 145 to estimate psi. The exact factor is 145.038, so the round-number shortcut introduces a 0.03% error — negligible for any practical engineering decision. 10 MPa × 145 = 1,450 psi (true: 1,450.4). 50 MPa × 145 = 7,250 psi (true: 7,251.9).
For the reverse, divide psi by 145 to estimate MPa: 5,000 psi ÷ 145 = 34.5 MPa (true: 34.47). The factor of 145 is the easiest number to remember in metric-imperial pressure work, and it stays accurate enough to use directly without further refinement in field conditions.
MPa × 145 ≈ psi (error 0.03%)psi ÷ 145 ≈ MPa (error 0.03%)MPa × 10 = bar (exact)MPa × 1000 = kPa (exact)20 MPa ≈ 2,900 psi (concrete C20)Common MPa to psi mistakes
The most common error is the kPa-versus-MPa prefix confusion described above. A tire pressure spec at 220 kPa is not 220 MPa; the latter would be enough to deform the rim. Always read the unit letter before the conversion.
The second common error is mixing gauge and absolute pressure. A pressure gauge on a hydraulic system reads gauge pressure (above atmospheric); engineering calculations and material strengths refer to absolute pressure (above zero). For most MPa-to-psi conversions the absolute vs. gauge distinction does not matter, because the offset is 0.1 MPa (atmospheric) on both sides. For low-pressure work the offset becomes significant.
Related pressure conversions
MPa connects to a network of pressure units through fixed factors. The most-used relations: MPa to kPa (×1,000), MPa to bar (×10), MPa to atm (×9.869), MPa to psi (×145.038), MPa to kgf/cm² (×10.197). All of them trace back to the SI pascal definition.