Megapascals to Pounds per square inch (MPa to psi)
Last updated:
Megapascals-to-psi conversions translate the SI-canonical high-pressure engineering unit (MPa, used universally in EU/Australia/NZ hydraulics, materials-strength testing, and high-pressure machining) into US-customary pounds-per-square-inch for US-trained hydraulic-engineering, structural-engineering and materials-testing work. A 25 MPa industrial hydraulic-system working pressure rolls down to 3626 psi for the US-trained service technician; a 275 MPa structural-steel yield strength rolls down to 39,886 psi or 39.9 ksi for the US-customary structural-engineering reference; a 350 MPa water-jet cutting pressure rolls down to 50,763 psi for the US-trained machinist. The conversion runs at every metric-MPa-spec to US-customary-psi destination boundary, particularly common in cross-Atlantic hydraulic-equipment service, structural-steel grade comparison, and high-pressure machining specifications.
How to convert Megapascals to Pounds per square inch
Formula
psi = MPa × 145.038
To convert megapascals to psi, multiply the MPa figure by 145.038 — equivalently, divide by 0.00689476, the MPa value of one psi. The factor follows from the SI-derived definition of one psi as 6894.757 Pa, with the MPa-to-Pa relationship at 1,000,000 Pa per MPa. For mental math, "MPa × 145" understates by about 0.03%, essentially identical to the precise factor; "MPa × 150" overstates by about 3.4%, fine for casual conversation but unsuitable for precision work. For US-trained hydraulic-equipment service, structural-engineering material-spec translation, high-pressure water-jet operator references, and concrete-strength grade comparison, use the full 145.038 multiplier on a calculator. The conversion runs at every metric-MPa-spec to US-customary-psi destination boundary, particularly common in cross-Atlantic hydraulic-equipment service.
Worked examples
Example 1 — 1 MPa
One megapascal — exactly 1,000,000 Pa or 10 bar — converts to 1 × 145.038 = 145.04 psi. That is the canonical MPa-to-psi reference and a useful benchmark for cross-jurisdictional pressure comparisons. The "1 MPa = 145 psi" rounded reference is taught in US-trained engineering education for quick mental conversion.
Example 2 — 25 MPa
Twenty-five megapascals — a typical EU industrial hydraulic-cylinder working pressure — converts to 25 × 145.038 = 3625.9 psi, typically rounded to 3626 psi on US-trained service-gauge displays. That is the figure on the US-shop pressure gauge during a routine EU-equipment hydraulic-service operation, with the MPa-figure on the EU manufacturer spec and the psi-figure on the US-trained operator's gauge.
Example 3 — 275 MPa
Two hundred and seventy-five megapascals — the minimum yield strength of EU structural steel grade S275 under EN 10025 — converts to 275 × 145.038 = 39,886 psi or 39.9 ksi. That is the figure on the US-customary structural-engineering material-spec sheet for cross-Atlantic comparison against ASTM A572 Grade 36 (248 MPa / 36 ksi) and Grade 50 (345 MPa / 50 ksi) US-customary grades.
MPa to psi conversion table
| MPa | psi |
|---|---|
| 1 MPa | 145.0377 psi |
| 2 MPa | 290.0755 psi |
| 3 MPa | 435.1132 psi |
| 4 MPa | 580.151 psi |
| 5 MPa | 725.1887 psi |
| 6 MPa | 870.2264 psi |
| 7 MPa | 1015.2642 psi |
| 8 MPa | 1160.3019 psi |
| 9 MPa | 1305.3396 psi |
| 10 MPa | 1450.3774 psi |
| 15 MPa | 2175.5661 psi |
| 20 MPa | 2900.7548 psi |
| 25 MPa | 3625.9434 psi |
| 30 MPa | 4351.1321 psi |
| 40 MPa | 5801.5095 psi |
| 50 MPa | 7251.8869 psi |
| 75 MPa | 10877.8303 psi |
| 100 MPa | 14503.7738 psi |
| 150 MPa | 21755.6607 psi |
| 200 MPa | 29007.5475 psi |
| 250 MPa | 36259.4344 psi |
| 500 MPa | 72518.8688 psi |
| 750 MPa | 108778.3033 psi |
| 1000 MPa | 145037.7377 psi |
| 2500 MPa | 362594.3443 psi |
| 5000 MPa | 725188.6885 psi |
Common MPa to psi conversions
- 1 MPa=145.0377 psi
- 5 MPa=725.1887 psi
- 10 MPa=1450.3774 psi
- 20 MPa=2900.7548 psi
- 25 MPa=3625.9434 psi
- 30 MPa=4351.1321 psi
- 50 MPa=7251.8869 psi
- 100 MPa=14503.7738 psi
- 200 MPa=29007.5475 psi
- 500 MPa=72518.8688 psi
What is a Megapascal?
The megapascal (MPa) is exactly 1,000,000 pascals or exactly 1000 kilopascals, where one pascal equals one newton of force distributed over one square metre of area. The relationship is fixed by SI prefix and SI-derived-unit definition, with the mega- prefix denoting exactly 10⁶. Standard atmospheric pressure at sea level (101,325 Pa) equals approximately 0.101 MPa — too small a figure for atmospheric reporting, where kPa or hPa is the natural unit. The megapascal is the SI-canonical engineering unit for higher-pressure-range applications: hydraulic-system working pressures (5-35 MPa typical), materials-strength testing (yield and ultimate strength 200-2000 MPa for engineering metals), high-pressure water-jet cutting (200-400 MPa), high-pressure die-casting and forging (50-300 MPa). The recognised SI symbol is "MPa", with the uppercase "M" SI prefix (mega-, 10⁶) and the uppercase "Pa" honouring Pascal. The case convention distinguishes M (mega, 10⁶) from m (milli, 10⁻³) — substituting one for the other gives a billion-fold error.
The megapascal emerged alongside the kilopascal as the SI multiple-of-pascal pressure unit for the higher-pressure-range engineering applications where the kPa scale would produce unwieldy four-and-five-digit figures. The pascal was named at the 14th CGPM in 1971, and the megapascal as the everyday-engineering multiple for hydraulics, materials-strength testing and high-pressure industrial processes was an immediate consequence: a typical industrial hydraulic cylinder runs at 20-30 MPa (rather than 20,000-30,000 kPa or 200-300 bar), a structural-steel yield strength is reported in 250-450 MPa (rather than 250,000-450,000 kPa), and a high-pressure water-jet cutting system runs at 200-400 MPa. The MPa scale legibly spans the full higher-pressure-engineering envelope from hydraulic systems through materials-strength testing into ultra-high-pressure machining. ISO 80000-4 standardises MPa as the default SI engineering pressure unit for the high-pressure applications, and ISO 6892-1 (tensile-testing of metallic materials) denominates yield strength, ultimate tensile strength and elastic modulus in MPa or GPa for the structural-engineering reference values.
Hydraulic engineering: industrial-hydraulic-cylinder working pressures (20-30 MPa typical), excavator and construction-equipment hydraulics (25-35 MPa), aerospace-hydraulic systems (20-35 MPa), high-pressure laboratory hydraulic test systems (50-100 MPa). The MPa scale spans the full hydraulic-engineering envelope without resorting to higher-prefix multiples. Materials-strength testing: yield strength and ultimate tensile strength of structural metals are universally reported in MPa under ISO 6892-1 — typical structural steel 250-450 MPa yield, automotive HSLA steel 350-700 MPa, aerospace titanium alloys 800-1100 MPa, ultra-high-strength steels 1500-2000 MPa, advanced fibre composites 1000-3000 MPa. Elastic modulus runs in GPa (200 GPa for steel, 70 GPa for aluminium, 110 GPa for titanium). High-pressure machining: water-jet cutting systems run at 200-400 MPa working pressure, with abrasive water-jet at the upper end of that range. Cold-isostatic pressing for ceramics and metal-injection-moulded parts runs at 100-400 MPa. Concrete strength: concrete-cube compression-strength testing under EN 12390 reports cube strength in MPa, with typical structural-concrete grades C25/30 (25 MPa cylinder strength, 30 MPa cube strength) through C50/60 and high-strength concretes above 80 MPa. Polymer mechanical properties: tensile strength and flexural modulus of engineering plastics are reported in MPa under ISO 527 — typical engineering polymers 30-100 MPa tensile strength.
What is a Pound per square inch?
One pound per square inch (psi) is the pressure exerted by a force of one pound-force (lbf) acting on an area of one square inch. By substitution from the 1959 International Yard and Pound Agreement values for the pound and the inch, and using standard gravity (9.80665 m/s²) for the conversion of pound-mass to pound-force, one psi equals exactly 6,894.757293168 pascals — typically rounded to 6,894.76 Pa or 6.895 kPa in engineering tables. The conversion to bar is 1 bar = 14.5037738 psi (or, going the other way, 1 psi ≈ 0.0689476 bar); to standard atmospheres 1 atm = 14.6959488 psi; to kilopascals 1 psi = 6.89476 kPa. Three closely related variants demand careful disambiguation in engineering writing: psia (pounds per square inch absolute) measures pressure relative to a perfect vacuum; psig (pounds per square inch gauge) measures pressure relative to local atmospheric pressure, so psig + ~14.696 = psia at standard sea-level conditions; and psid (pounds per square inch differential) measures the pressure difference between two points in a system. A tyre gauge reading "30 psi" is reporting psig — the actual absolute pressure inside the tyre is closer to 44.7 psia. Conflating absolute and gauge readings is one of the most common sources of engineering error when using the unit, particularly in thermodynamic calculations where the perfect-gas equation requires absolute pressure.
The pound per square inch is a compound unit, not a primitively defined one — it inherits its magnitude from the avoirdupois pound and the international inch via the 1959 International Yard and Pound Agreement, which fixed the pound at exactly 0.45359237 kilograms and the inch at exactly 0.0254 metres. No single treaty, statute or weights-and-measures act defines psi independently; the unit emerged from nineteenth-century engineering practice as steam power, hydraulics and pneumatics needed a working measure of force per area in the imperial system already standard in British and American workshops. The Bourdon-tube pressure gauge, patented in France in 1849 by Eugène Bourdon and rapidly adopted across Anglo-American steam engineering, was the instrument that put psi readings on the workshop wall; James Watt's earlier indicator diagrams had already established pressure-times-volume thinking in pounds and inches a century before. Through the late nineteenth and early twentieth centuries the American Society of Mechanical Engineers (founded 1880), the Society of Automotive Engineers (founded 1905) and the American Petroleum Institute consolidated psi as the working pressure unit across US industrial standards, and the unit was reinforced in practice by every industry that grew up around imperial fasteners, fittings and gauge faces. Capitalisation is conventional rather than rule-bound: engineering style guides and ASME publications write the unit lower-case ("psi"), reflecting that the abbreviation stands for a descriptive phrase rather than a proper noun. Consumer-facing tyre gauges, air-compressor labels and hardware-store signage render it upper-case ("PSI"), reflecting the unit's split life as both a precision engineering quantity and a piece of everyday American vocabulary.
US automotive engineering is the consumer-facing centerpiece of psi. The Federal Motor Vehicle Safety Standard 138, promulgated by NHTSA and effective for all light vehicles sold in the United States since model year 2008, mandates tyre-pressure monitoring systems (TPMS) and specifies recommended cold-tyre inflation pressures in psi on the vehicle's door-jamb placard — typically in the 30–35 psi range for passenger cars and 35–40 psi for light trucks. The Society of Automotive Engineers (SAE) standards for hydraulic brake-fluid working pressures, fuel-system pressures and engine oil pressures are all denominated in psi, and every gas-station air pump in the United States reads in psi. US compressed-gas and pressure-vessel engineering: the Compressed Gas Association (CGA) cylinder standards, the Department of Transportation (DOT) cylinder specifications (DOT-3AA for steel high-pressure cylinders, DOT-4B for low-pressure refrigerant cylinders), and the ASME Boiler and Pressure Vessel Code all specify pressures in psi for the US market. A standard medical oxygen E-cylinder is rated at 2,200 psi service pressure; an industrial nitrogen K-cylinder runs at 2,640 psi; a typical home propane tank fills to about 200 psi at summer temperatures. US industrial hydraulics: Parker Hannifin, Eaton and Bosch Rexroth (in their North American product lines), together with the National Fluid Power Association, spec hydraulic pumps, valves, hoses and cylinders in psi for US-market documentation, with mobile-equipment hydraulics running 2,500–4,000 psi and aerospace hydraulic systems at 3,000 psi or 5,000 psi (the latter on newer fly-by-wire airframes for weight savings). The identical Parker product sold into Europe is catalogued in bar. US plumbing and water systems: the Uniform Plumbing Code and the International Plumbing Code, both adopted by US states and municipalities, specify residential water-supply pressures in psi (40–80 psi typical, with code-mandated pressure-reducing valves required above 80 psi). US HVAC refrigerant pressures — R-410A at about 118 psi suction and 418 psi discharge in a typical air-conditioning operating cycle — are specified in psi on every US-market refrigeration gauge manifold. Firearms: the Sporting Arms and Ammunition Manufacturers' Institute (SAAMI), the US industry standards body, publishes maximum chamber pressures in psi for US-market cartridges (.308 Winchester at 62,000 psi, 9mm Luger at 35,000 psi, .223 Remington at 55,000 psi). The Permanent International Commission for the Proof of Small Arms (CIP), the European counterpart, publishes the corresponding pressures in bar or megapascals — which is why a SAAMI 9mm and a CIP 9×19 Parabellum are nominally the same cartridge with subtly different pressure specifications and slightly different proof-test methodologies. International scope: psi is essentially a US and US-influenced industrial unit. The UK retains psi alongside bar for tyre pressure on gas-station gauges and on the printed cards that come with bicycle pumps, but European automotive specifications, EU industrial machinery directives under the Pressure Equipment Directive 2014/68/EU, and most of the rest of the world denominate pressure in bar or kilopascals. The United States is the only major economy where consumer-facing pressure measurement is dominated by a single non-SI unit, and a US-market product simultaneously sold into Europe will typically carry both psi and bar markings on its label or gauge face.
Real-world uses for Megapascals to Pounds per square inch
EU hydraulic-system MPa working pressures translated to US-trained psi service work
EU-manufactured industrial hydraulic systems (Bosch Rexroth, Eaton-Vickers EU, Parker-Hannifin EU operations, Atos Italian hydraulic specialists) specify working pressures in MPa on the engineering primary documentation but the US-trained service technician working on equipment imported into US industrial settings reads psi on the gauge. A 25 MPa industrial hydraulic-cylinder working pressure rolls down to 3626 psi on the US-shop pressure gauge; a 35 MPa heavy-construction-equipment hydraulic spec rolls down to 5076 psi. The conversion runs at every EU-equipment hydraulic-service operation in US settings, with the MPa-figure on the EU manufacturer spec and the psi-figure on the US-trained operator's gauge.
EU structural-steel MPa yield strengths translated to US-customary ksi grade designations
EU-jurisdiction structural-steel grade designations (S275 with 275 MPa yield, S355 with 355 MPa yield, S460 with 460 MPa yield under EN 10025) translate to US-customary ksi grade designations (Grade 36 ksi at 248 MPa, Grade 50 ksi at 345 MPa, Grade 65 ksi at 448 MPa under ASTM A572) for cross-jurisdictional structural-engineering comparison. A 275 MPa S275 EU steel rolls down to 39,886 psi or 39.9 ksi — close to but not identical to the US-customary 36 ksi or 50 ksi grade. The conversion runs at every cross-Atlantic structural-engineering material-spec translation.
EU high-pressure water-jet MPa specs translated to US-customary psi machinist references
EU-manufactured high-pressure water-jet cutting equipment (KMT Waterjet, Flow International EU operations, Resato from the Netherlands, Bft Hammelmann from Germany) specifies working pressures in MPa on the manufacturer documentation but the US-trained machinist operating the equipment reads psi on the operator-control panel. A 350 MPa abrasive water-jet cutting pressure rolls down to 50,763 psi on the US-trained operator console; a 400 MPa premium-class water-jet rolls down to 58,015 psi. The conversion runs at every EU-equipment water-jet service operation in US machine shops.
EU concrete-strength MPa grade designations translated to US-customary psi compressive strength
EU concrete-grade designations under EN 12390 (C25/30 with 25 MPa cylinder strength, C30/37 with 30 MPa, C40/50 with 40 MPa) translate to US-customary psi compressive strength under ACI 318 (Class A at 3000-5000 psi, structural at 4000-5000 psi, high-strength above 6000 psi) for cross-jurisdictional structural-engineering comparison. A 30 MPa C30/37 EU concrete grade rolls down to 4351 psi compressive strength on the US-customary structural-engineering reference; a 50 MPa high-strength concrete rolls down to 7252 psi. The conversion runs at every cross-Atlantic structural-concrete grade comparison.
When to use Pounds per square inch instead of Megapascals
Use psi whenever the destination is a US-trained hydraulic-equipment service gauge, US-customary structural-engineering material-spec sheet, US-trained machinist water-jet operator console, US-customary concrete-strength reference, or any US-trained engineering context where psi or ksi is the everyday unit. Psi is the universal US-customary high-pressure engineering unit across hydraulics, structural-steel grading, water-jet machining and structural-concrete documentation. Stay in megapascals when the destination is an EU manufacturer spec sheet, EN-standard structural-steel grade, EN 12390 concrete-grade designation, EU water-jet equipment manufacturer documentation, or any document calibrated to the SI-derived metric pressure system. The conversion is at the metric-MPa-spec to US-customary-psi-execution boundary, with the MPa figure on the source-design side and the psi figure on the US-trained operational-execution side.
Common mistakes converting MPa to psi
- Treating "MPa × 145" as exact precision for ksi-grade structural-steel comparison. The 0.03% rounding error is invisible at typical structural-engineering precision but can introduce small inconsistencies in safety-factor calculations across cross-Atlantic engineering reviews. The full 145.038 multiplier is required for precision-engineering documentation; the rounded "× 145" is fine for casual mental conversion.
- Confusing MPa-to-psi (multiply by 145) with kPa-to-psi (multiply by 0.145). Both are within-pressure cross-jurisdictional conversions but at different scale steps, and mixing them up gives a thousandfold error. The standard pressure hierarchy is 1 MPa = 1000 kPa = 145 psi, with the kPa-to-psi factor (0.145) and the MPa-to-psi factor (145) differing by a factor of 1000.
Frequently asked questions
How many psi in 1 MPa?
One megapascal equals 145.038 psi at the precise SI-derived definition. The factor follows from the canonical relationship 1 psi = 6894.757 Pa, with megapascals as 1,000,000 Pa per MPa giving the 145.038 conversion factor. The figure is exact rather than approximate. The "1 MPa ≈ 145 psi" rounded reference is taught in US-trained engineering education for quick mental conversion.
How many psi in 25 MPa (a typical hydraulic pressure)?
Twenty-five megapascals equals 25 × 145.038 = 3625.9 psi, typically rounded to 3626 psi on US-trained service-gauge displays. That is a typical EU industrial hydraulic-cylinder working pressure, with the MPa-figure on the EU manufacturer spec and the psi-figure on the US-shop service gauge. The conversion runs at every EU-equipment hydraulic-service operation in US industrial settings.
How many psi in 275 MPa (S275 structural steel yield strength)?
Two hundred and seventy-five megapascals equals 275 × 145.038 = 39,886 psi or 39.9 ksi. That is the minimum yield strength of EU structural steel grade S275 under EN 10025, with the MPa-figure on the EN-standard material spec and the ksi-figure on the US-customary structural-engineering material reference. The S275 grade sits between US-customary ASTM A572 Grade 36 (248 MPa / 36 ksi) and Grade 50 (345 MPa / 50 ksi).
Quick way to convert MPa to psi in my head?
Multiply the MPa figure by 145 — the precision is to about 0.03%, essentially identical to the precise 145.038 multiplier. For 25 MPa the shortcut gives 3625 psi versus the precise 3626 psi. The "MPa × 150" cruder shortcut overstates by about 3.4% and is fine for casual conversation but unsuitable for precision engineering work. The "× 145" mental shortcut is a common US-engineering-education benchmark.
What is the difference between MPa and ksi?
MPa (megapascal) is the SI-derived engineering pressure unit at 1,000,000 Pa per MPa; ksi (kilopound per square inch) is the US-customary engineering pressure unit at 1000 psi per ksi. The two are related by 1 MPa = 0.145038 ksi, so a 275 MPa structural-steel yield strength equals 39.9 ksi. Cross-jurisdictional structural-engineering documentation typically shows both, with MPa as the SI-canonical primary and ksi as the US-customary reference.
How does MPa-to-psi connect to bar-to-psi?
One MPa equals 10 bar (since 1 bar = 100 kPa and 1 MPa = 1000 kPa), so MPa-to-psi factor of 145 equals ten times the bar-to-psi factor of 14.5. The two scale ratios are consistent with the underlying pascal-based SI definitions. For everyday EU hydraulic-engineering, bar appears for the lower 0.1-100 bar range and MPa appears for the higher 1-100 MPa range.
How precise should MPa-to-psi be for hydraulic service work?
For US-trained hydraulic-equipment service work the precise 145.038 multiplier is required because hydraulic-cylinder working-pressure tolerances are typically ±5% and the cumulative conversion error must stay well within that band. The "MPa × 145" shortcut is precise to 0.03% and is acceptable for almost all operational service work; the "MPa × 150" shortcut introduces a 3.4% error and is unsuitable for precision-equipment service.