Convert Pressure from pounds per square inch to megapascals (psi to MPa)

Pound per Square Inch to Megapascal Conversion Formula

To convert a pressure or stress from pounds per square inch (psi) to megapascals (MPa), multiply by 0.00689476.

• MPa = psi × 0.00689476

Because the factor is awkward at this scale, engineering practice leans on the thousand-fold version: 1 ksi (1,000 psi) = 6.89476 MPa. Stress values in US materials tables are usually quoted in ksi precisely so that the MPa conversion is a single clean multiplication.

Step-by-Step Example

A US structural drawing calls for A36 steel, minimum yield strength 36,000 psi, and the analysis software is configured in SI:

1. Take the stress: 36,000 psi (36 ksi)
2. Multiply by 0.00689476: 36,000 × 0.00689476 = 248.2 MPa

That 248 MPa figure is exactly how the same steel grade appears in metric references.

Quick Reference Table

Stress, Not Just Pressure

The psi-to-MPa conversion lives mostly in materials engineering, where the quantity is stress — force per unit of cross-section — rather than fluid pressure, and the numbers run thousands of times higher than anything a pipe gauge shows. Concrete is the everyday example: American practice specifies compressive strength as 3,000/4,000/5,000 psi concrete, while the rest of the world writes 20/25/30 MPa for the same grades (the round metric numbers and the round imperial numbers do not quite coincide — 4,000 psi is 27.6 MPa, not 25 — so "equivalent" grades in tables are conventions, not conversions). Steel properties, bolt proof loads, weld strengths and pressure-vessel allowables repeat the pattern, with ksi as the imperial working unit.

One consequence of the stress context: gauge-versus-absolute, the trap that haunts every fluid-pressure conversion, is irrelevant here — stress has no atmosphere to be relative to. The trap that replaces it is precision theater. A yield strength known to two significant figures does not become better known by being converted to 248.2114 MPa; matching the stated precision of the source figure is part of converting it correctly.

How many pounds per square inch are in one megapascal? One megapascal (MPa) contains 145.03768078 pounds per square inch (psi) — the inverse of the factor above. Multiplying by 0.0068947600004501395751 takes you from pounds per square inch to megapascals; multiplying by 145.03768078 brings you back.

Put in words: one pound per square inch equals 0.0068947600004501395751 megapascals, so the pound per square inch is the smaller unit of this pair. Converting between them never changes the amount of pressure being measured — only the size of the unit you count it in.

What is a pound per square inch (psi)?

A pound per square inch (PSI) is a unit of pressure commonly used in the imperial system (which is standard in the United States).

It measures the amount of force applied over a single square inch of area.

Common Examples of PSI (Where is PSI Used?)

PSI is a critical measurement for safety and performance in many common items, including:

• Vehicle Tires: Proper tire pressure (PSI) ensures optimal handling, fuel efficiency, and tire life. You can find the recommended level on a sticker inside the driver's door.

• Home Water Pressure: Affects everything from shower performance to how well appliances like dishwashers and washing machines function.

• Sports Equipment: Items like footballs, basketballs, and soccer balls require a specific PSI to perform correctly and safely.

• Tools: Air compressors, pressure washers, and paint sprayers all have specific PSI ratings for safe and effective operation.

Converting PSI to Metric Units like Pascals and Bar

While PSI is standard in the imperial system, scientific and international contexts use metric (SI) units like the Pascal (Pa) and the bar.

• PSI to Pascal (Pa): The official SI unit for pressure.
  1 PSI ≈ 6,894.76 Pascals (or 6.895 kilopascals, kPa).

• PSI to Bar: A common unit in automotive and weather contexts. 1 bar is roughly equal to atmospheric pressure at sea level.
  1 PSI ≈ 0.0689 bar.

Understanding the Types of PSI: PSIG, PSIA, and PSID

The term "PSI" can be specified further to give more context:

• PSIG (Pound-force per square inch gauge): Measures pressure relative to the surrounding atmospheric pressure. This is the most common measurement, used by a standard tire gauge.

• PSIA (Pound-force per square inch absolute): Measures pressure relative to a perfect vacuum (absolute zero pressure).
  The formula is: PSIA = PSIG + local atmospheric pressure.

• PSID (Pound-force per square inch differential): Measures the difference in pressure between two separate points in a system, such as across a filter or valve.

What is a megapascal (MPa)?

If you've ever looked at engineering specifications, construction materials, or high-pressure equipment, you've likely seen the term 'MPa.'

A megapascal (MPa) is a unit of pressure in the metric system, equal to one thousand kilopascals (1000 kPa).

The plural form is megapascals.

Using MPa to Measure Material Strength

The megapascal (MPa) is a fundamental unit for quantifying the strength of materials in engineering and construction.

It is commonly used to express a material's ultimate tensile strength (the maximum stress it can withstand while being pulled apart) and compressive strength (its resistance to being squeezed).

For example, structural steel might have a tensile strength of 400 MPa. In comparison, high-performance concrete can have a compressive strength exceeding 80 MPa.

MPa to PSI and Bar Conversions (and kPa)

Understanding how to convert megapascals to other pressure units is crucial for global applications.

Here are the most common conversions:

• 1 MPa = 1,000 kilopascals (kPa)
• 1 MPa = 145.04 pounds per square inch (PSI)
• 1 MPa = 10 bar

The pound per square inch (PSI) is a unit commonly used in the United States for measuring tire pressure and hydraulic systems.

The bar is a unit often used in Europe for weather forecasting and scuba diving.

Real-World Examples of Megapascal Pressures

Megapascals are used to describe immense pressures found in both natural and industrial settings.

The water pressure at the bottom of the Mariana Trench, the deepest point in the ocean, is about 108.6 MPa.

In industry, a high-pressure waterjet cutter operates at pressures ranging from 200 to 600 MPa, demonstrating enough force to slice through metal and stone.

pound per square inch to megapascal Conversion Table

Here are some quick reference conversions from pound per square inch (psi) to megapascal (MPa):

This conversion in other languages

Engineering datasheets across Europe write pound per square inch to megapascal several different ways. The calculation is the same in every one of them.