MPa to PSI Conversion

The MPa to PSI conversion calculator is bidirectional. It derives psi from the pound-force and exact inch relationships, then rounds the displayed factor.

This page is intentionally narrower than a pressure hub. It focuses on the moment a metric engineering value must be compared with a psi value. Use MPa conversion when you want bar, atm, kPa, and Pa at the same time. Use the kPa converter when the starting value is in kilopascals. If your problem involves gauge pressure and atmospheric offsets, read the bar to PSIG converter before assuming a psi number is absolute.

Unit definitions

A pascal is one newton per square meter. A megapascal is one million pascals, so it is well sized for material strength and high-pressure equipment. Psi is pounds-force per square inch, an imperial pressure unit based on force distributed over area. The two units measure the same dimension, but their unit sizes are very different: one MPa is about 145 psi, so the number grows when converting from MPa to psi and shrinks when converting from psi to MPa.

Because stress and pressure share dimensions, this calculator works for both. A concrete cylinder test, a steel yield-strength table, a hydraulic accumulator, and a pressure vessel can all use the same factor. What the calculator does not know is whether the value is gauge, absolute, differential, tensile, compressive, or allowable stress. Preserve that context in your notes.

Formula

The calculation uses a single constant:

$\text{psi per MPa} = 145.03773773020922$

For MPa to psi:

$\text{psi} = \text{MPa} \times 145.0377$

For psi to MPa:

$\text{MPa} = \frac{\text{psi}}{145.0377}$

The result row displays the converted pressure with as many as six decimal places, while the factor row displays 145.0377 psi per MPa.

Worked example

Suppose a pressure washer is rated at 20 MPa and you need the equivalent psi for a U.S. comparison. With the MPa-to-psi direction selected, the calculator performs:

$\text{psi} = 20 \times 145.0377 = 2900.754$

The primary result is 2900.754 psi. The item rows show the conversion factor as 145.0377 psi per MPa, the input pressure as 20 MPa, and the converted pressure as 2900.754 psi. If you reverse the problem and enter 2900.754 psi, the calculator divides by 145.0377 and returns 20 MPa.

Reference table

Materials, hydraulics, and specifications

In materials work, MPa is often the native unit. Concrete may be ordered by compressive strength, metals by yield or tensile strength, plastics by tensile strength, and adhesives by lap-shear strength. When those values are sent to a shop, inspection form, or U.S. customer, psi may be requested. The conversion is simple, but the test condition is not: always keep the material standard, specimen direction, temperature, and safety factor separate from the unit conversion.

In fluid-power work, MPa can describe pump discharge pressure, hydraulic cylinder pressure, accumulator precharge, or relief-valve settings. Many gauges in the same shop may be labeled in psi. The conversion helps catch orders of magnitude: 12 MPa is about 1740 psi, not 174 psi. For atmosphere-related pressure comparisons, the psi to atm conversion can show how many standard atmospheres a psi reading represents. For bar-based equipment, bar to psi gives a neighboring industrial pair.

Precision and pitfalls

The first pitfall is multiplying in the wrong direction. MPa-to-psi multiplies; psi-to-MPa divides. The second is confusing MPa with kPa. One MPa is 1,000 kPa, so a misplaced prefix can turn a safe pressure into an impossible one. The third is ignoring pressure reference. Psi can be psia, psig, or simply a shorthand label. If the original value is gauge pressure, the converted MPa is also gauge pressure. If it is absolute pressure, the converted MPa is absolute pressure.

Rounding should follow the source. A value printed as 35 MPa may support fewer significant figures than the calculated 5076.3195 psi display. Keep full precision while checking, then choose a final rounded value that matches the drawing, gauge resolution, or material-test report.

Accuracy and limits

The raw calculation uses the dimensional factor above; 145.0377 in explanatory text is shorthand, not the stored basis.

Sources

• NIST, Guide for the Use of the International System of Units — SI unit and conversion-factor guidance.
• BIPM, The International System of Units brochure — official SI definitions for the pascal and prefixes.
• NIST, SI units overview — practical explanation of SI units and derived units.