Pressure Converter

Convert between pressure units instantly.

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Quick Conversions

What Is a Pressure Converter?

A pressure converter is a tool that translates pressure values between different units of measurement. Pressure is the force applied per unit area and is measured in many different units depending on the application, region, and industry. Engineers use pascals and megapascals, automotive technicians use PSI, meteorologists use millibars, medical professionals use millimeters of mercury, and scientists use atmospheres. This converter handles all of these units and more.

Being able to convert pressure units accurately is critical in fields ranging from industrial manufacturing to healthcare. Hydraulic system specifications may arrive in PSI from American suppliers and in bar from European ones. Blood pressure monitors display mmHg while scientific papers report pressure in kilopascals. This tool ensures that you can work seamlessly across all these standards.

How Pressure Conversion Works

Every pressure conversion in this calculator passes through the pascal as the base unit. The pascal is the SI standard for pressure, defined as one newton per square meter. Each supported unit has a defined conversion factor that relates it to the pascal.

To convert from one unit to another, the calculator multiplies the input value by its source unit's conversion factor to obtain pascals, then divides by the target unit's conversion factor. For example, converting 1 atm to PSI: 1 times 101,325 (pascals per atm) divided by 6,894.76 (pascals per PSI) equals approximately 14.696 PSI.

The conversion factors are based on internationally recognized definitions. One atmosphere is defined as exactly 101,325 pascals. One bar is defined as exactly 100,000 pascals. One PSI is defined using the pound-force and square inch, yielding approximately 6,894.76 pascals. These precise relationships ensure that conversions are accurate to the limits of floating-point arithmetic.

How to Use This Converter

Enter the pressure value in the input field on the left side of the form. You can type any numeric value including decimals and negative numbers for gauge pressures.
Select the source unit from the dropdown below the input. Eight common pressure units are available: Pascal, Kilopascal, Megapascal, Bar, PSI, Atmosphere, Torr, and mmHg.
Select the target unit from the dropdown on the right side. The converted result appears instantly.
Use the swap button to reverse the conversion direction, keeping your numeric value in place.
Try the quick conversion buttons for common reference values: 1 atmosphere (standard pressure), 14.696 PSI (sea level), 1 bar (common industrial), and 32 PSI (typical tire pressure).
Review the complete conversion grid that shows your input expressed in every supported unit simultaneously.

Worked Examples

Example 1: Tire Pressure

A tire inflated to 35 PSI. Converting to bar: 35 times 6,894.76 equals 241,316.6 pascals, divided by 100,000 equals 2.413 bar. Converting to kPa: 241.317 kPa. This explains why European tire markings often show values around 2.4 bar.

Example 2: Blood Pressure Reading

A blood pressure of 120 mmHg (systolic). Converting to kPa: 120 times 133.322 equals 15,998.64 pascals, or approximately 16.0 kPa. Some international medical standards report blood pressure in kilopascals, making this conversion relevant for healthcare professionals working across different systems.

Example 3: Atmospheric Pressure at Altitude

At 5,000 feet elevation, atmospheric pressure is approximately 12.23 PSI. Converting: 12.23 times 6,894.76 equals 84,303 pascals, or 0.832 atm. This is about 83 percent of standard sea-level pressure, which affects cooking times, engine performance, and human physiology.

Example 4: Hydraulic System

A hydraulic press operates at 25 MPa. Converting to PSI: 25,000,000 divided by 6,894.76 equals approximately 3,626 PSI. In bar: 25,000,000 divided by 100,000 equals 250 bar. These conversions are necessary when sourcing components from international suppliers with different rating standards.

Common Use Cases

Automotive maintenance: Convert tire pressure between PSI and bar when using gauges or following manufacturer specifications from different regions.
Medical practice: Translate blood pressure readings between mmHg and kilopascals for international medical record compatibility.
Industrial engineering: Convert hydraulic and pneumatic system pressures between PSI, bar, and MPa when working with equipment from different manufacturers.
Meteorology: Convert barometric pressure between hectopascals (same as millibars), inches of mercury, and atmospheres for weather reporting.
Scuba diving: Calculate underwater pressures in atmospheres or bar for dive planning and equipment compatibility.
HVAC and refrigeration: Convert refrigerant pressures between PSI and bar when servicing systems rated in different standards.

Tips and Common Mistakes

Distinguish between absolute and gauge pressure. Absolute pressure is measured from a perfect vacuum, while gauge pressure is measured relative to atmospheric pressure. Gauge pressure is zero at sea level, while absolute pressure is 1 atm. Most everyday measurements (tire pressure, blood pressure) are gauge pressures. Add atmospheric pressure to gauge pressure to get absolute pressure.

Remember that 1 bar is not exactly 1 atmosphere. One bar equals 100,000 pascals while one atmosphere equals 101,325 pascals. The difference of 1.325 percent may seem small but can matter in precise scientific calculations. For rough estimates they are interchangeable, but for accuracy use the exact conversion factors.

Be careful with millibar and hectopascal. In meteorology, 1 millibar equals exactly 1 hectopascal (100 pascals). Standard atmospheric pressure is 1013.25 millibars or 1013.25 hectopascals. These two units are numerically identical despite having different names.

Know which PSI convention applies. PSI (pounds per square inch) usually means gauge pressure (psig), but it can also mean absolute pressure (psia). When a specification says 100 PSI without further clarification, assume gauge pressure. When working with vacuum systems or scientific applications, check whether absolute or gauge readings are intended.

Use megapascals for high-pressure applications. Working in pascals for pressures above 1 MPa produces unwieldy numbers. Hydraulic systems, material tensile strengths, and high-pressure piping are typically specified in megapascals, keeping the numbers in a manageable range.

Frequently Asked Questions

What is the difference between PSI and bar?

PSI (pounds per square inch) is a pressure unit used primarily in the United States and is common in automotive and industrial applications. Bar is a metric unit widely used in Europe and scientific contexts. One bar equals approximately 14.504 PSI, and one PSI equals approximately 0.06895 bar. Both measure the same physical quantity but originate from different measurement traditions.

What is standard atmospheric pressure?

Standard atmospheric pressure is defined as 101,325 pascals, which equals 1 atmosphere (atm), 1.01325 bar, 14.696 PSI, or 760 mmHg. This is the average air pressure at sea level under standard conditions. It serves as a reference point for calibrating instruments and for defining other pressure-related standards in meteorology, aviation, and engineering.

How do I convert tire pressure between PSI and bar?

Divide the PSI value by 14.504 to get bar, or multiply bar by 14.504 to get PSI. A typical car tire inflated to 32 PSI equals approximately 2.21 bar. Many tire pressure gauges display both units. The converter provides instant results for any value, eliminating the need for manual calculation when switching between measurement systems.

What is a pascal and why is it the SI standard?

A pascal (Pa) is the SI unit of pressure defined as one newton of force per square meter of area. It integrates seamlessly with other SI units in physics and engineering equations. Because one pascal is very small, kilopascals (kPa) and megapascals (MPa) are more commonly used in practice. Standard atmospheric pressure is 101.325 kPa.

What is the relationship between torr and mmHg?

Torr and millimeters of mercury (mmHg) are nearly identical in practice. One torr was originally defined as the pressure exerted by a one-millimeter column of mercury. The modern definition makes 1 torr equal to exactly 1/760 of a standard atmosphere, which is 133.322 pascals. For all practical purposes, 1 torr equals 1 mmHg.

Where is mmHg commonly used?

Millimeters of mercury (mmHg) is the standard unit for blood pressure measurements in medicine. Normal blood pressure is approximately 120/80 mmHg. It is also used in laboratory vacuum measurements and in meteorology for barometric pressure readings. The unit originated from mercury manometers that physically measured pressure by the height of a mercury column.

What pressure units are used in scuba diving?

Scuba divers commonly use atmospheres (atm) or bar to express underwater pressure. Pressure increases by approximately 1 atm for every 10 meters of seawater depth. At 30 meters deep, the total pressure is about 4 atm (1 atmospheric plus 3 from the water). Tank pressures are typically rated in bar, with a full tank at 200 to 300 bar.

How do I convert between megapascals and PSI for hydraulic systems?

Multiply MPa by 145.038 to get PSI, or divide PSI by 145.038 to get MPa. Hydraulic systems commonly operate between 10 and 35 MPa (approximately 1,450 to 5,076 PSI). This conversion is essential when working with equipment rated in different unit systems or when interpreting specifications from international suppliers.