Pressure Converter

What Is a Pressure Converter?

A pressure converter translates force per unit area between pascals, bar, psi, atmospheres, torr, and millimeters of mercury. The pascal is the SI unit, defined as one newton per square meter. It is a small unit, so kilopascals and megapascals are more common in engineering. Bar is the everyday metric unit in Europe, where tire pressure reads 2.3 bar instead of 33 psi. Pounds per square inch dominates in the United States for tires, compressors, and plumbing. Atmospheres, torr, and mmHg come from meteorology and medicine, where blood pressure is still reported in millimeters of mercury.

You need pressure conversion when inflating tires to a European spec in bar, reading a weather report in millibars, comparing a scuba tank rated in psi to a European regulator in bar, or interpreting a blood pressure reading of 120/80 mmHg in pascals. For related physics, see our Pressure Calculator and Force Calculator.

What This Calculator Does

This converter handles ten common pressure units: pascals, kilopascals, megapascals, bar, millibar, psi, atmospheres, torr, millimeters of mercury, and inches of mercury. Enter a value, pick the source and target units, and the result appears instantly. A swap button reverses the direction, and a full table shows your input in every supported unit at once.

• Inputs: A numeric value, source unit, and target unit
• Outputs: Converted result, conversion details, and a table of all units

How the Conversion Works

The calculator first converts the input to pascals, the SI base unit, then divides by the target unit's pascal factor. One pascal is one newton per square meter. One standard atmosphere is defined as exactly 101,325 pascals. One bar is exactly 100,000 pascals, which is close to one atmosphere (1.01325 bar). One psi is the pressure exerted by one pound-force on one square inch, which equals 6,894.76 pascals. One torr is defined as 1/760 of an atmosphere, or about 133.322 pascals, and is nearly identical to one millimeter of mercury.

For example, converting 2.3 bar to psi: 2.3 times 100,000 equals 230,000 pascals. Dividing by 6,894.76 gives 33.36 psi. That is why a European tire pressure of 2.3 bar is roughly 33 psi on a US gauge. Converting 120 mmHg (systolic blood pressure) to kPa: 120 times 133.322 equals 15,999 pascals, or about 16.0 kPa.

Common Conversion Factors

How to Use the Calculator

1. Enter the pressure value you want to convert.
2. Select the unit you are converting from.
3. Select the unit you are converting to, or click swap to reverse the direction.
4. Read the result and the full conversion table below it.

Example Calculations

Example 1: Tire Pressure bar to psi

A car door sticker in Germany recommends 2.4 bar for the front tires. The driver has a US-made tire gauge that reads psi.

• Convert: 2.4 times 100,000 = 240,000 Pa
• In psi: 240,000 / 6,894.76 = 34.81 psi
• Result: about 35 psi, a common passenger car tire pressure

Example 2: Blood Pressure mmHg to kPa

A blood pressure reading of 120/80 mmHg needs to be expressed in kilopascals for a European medical form.

• Systolic: 120 times 133.322 = 15,999 Pa = 16.0 kPa
• Diastolic: 80 times 133.322 = 10,666 Pa = 10.7 kPa
• Result: 16.0/10.7 kPa, which is the normal adult range

Real-World Scenarios

Scuba Tank Pressure Across Borders

Liam, a diver from the US, is on a dive trip in Greece. His regulator and pressure gauge are calibrated in psi, but the dive shop fills tanks to 200 bar, the European standard. He needs to know what 200 bar means on his gauge. Using the converter, 200 bar equals 20,000,000 pascals, which is 2,900.75 psi. His US-rated aluminum 80 cubic foot tank holds 3,000 psi at full capacity, so 200 bar is just under a full fill. He also checks the working pressure of his regulator, rated to 4,500 psi, which is about 310 bar, well above what the shop will fill. For calculating his air consumption rate at depth, he references our Pressure Calculator.

HVAC Refrigerant Pressures

Sofia, an HVAC technician in Texas, services a system that uses R-410A refrigerant. The service manual lists the high-side operating pressure as 350 psig at 95 degrees F outdoor temperature. A European colleague asks for the value in bar. Using the converter, 350 psi equals 350 times 6,894.76 = 2,413,166 pascals, or 24.13 bar. She notes that the manual specifies psig (gauge pressure, above atmospheric), while the converter works in absolute pressure units, but for high pressures the 1 bar difference between gauge and absolute is negligible. She also checks the low-side pressure of 130 psig, which is 8.96 bar, to confirm the system is operating within the normal range for R-410A. For the cooling capacity in BTU, she uses our BTU Calculator.

Weather and Atmospheric Pressure

Raj, a private pilot, checks the weather before a flight. The METAR report gives the altimeter setting as 29.92 inHg, which is standard atmospheric pressure. He wants this in millibars for his European flight computer. Using the converter, 29.92 inHg equals 29.92 times 3,386.39 = 101,325 pascals, or 1,013.25 mbar, which is exactly 1 standard atmosphere. On a different day, the altimeter reads 30.15 inHg, a high-pressure system. Converting gives 30.15 times 3,386.39 = 102,106 pascals, or 1,021.06 mbar. He knows that higher pressure means higher density altitude correction, which affects takeoff distance. For the wind speed component of his preflight, he uses our Speed Converter.

Common Mistakes to Avoid

• Confusing gauge and absolute pressure: A tire gauge reads gauge pressure (psig), which is pressure above atmospheric. Absolute pressure (psia) adds one atmosphere (14.7 psi). A tire at 32 psig is 46.7 psia. Most everyday pressure readings are gauge. Vacuum and scientific measurements are often absolute. Always check which one a spec uses.
• Treating torr and mmHg as exactly equal: One torr is defined as 1/760 of a standard atmosphere (133.322 Pa). One conventional mmHg is 133.322 Pa based on mercury density at 0 degrees C. They differ by about 0.000015%, which is negligible for most uses but matters in precision vacuum work. This converter treats them as equivalent for practical purposes.
• Mixing up bar and pascal scales: One bar is 100,000 pascals, not 1,000. A common error is treating bar like kilopascal. 2.3 bar is 230,000 Pa (230 kPa), not 2,300 Pa. The factor of 100 matters in tire pressure and hydraulic calculations.
• Forgetting mercury density varies with temperature: The mmHg and inHg units assume mercury at 0 degrees C. At room temperature (20 C), mercury expands by about 0.36%, so a 760 mmHg column at 20 C exerts slightly less pressure than at 0 C. Medical blood pressure measurements ignore this small error, but precision barometers correct for temperature.

Authoritative Research and Resources

• NIST Metric SI Units - The National Institute of Standards and Technology defines the pascal as the SI derived unit of pressure (one newton per square meter) and maintains the standard atmosphere definition of 101,325 pascals used as the reference for all pressure conversions.
• NOAA National Weather Service - The U.S. weather agency that reports atmospheric pressure in millibars and inches of mercury, providing real-world examples of pressure unit usage in meteorology and aviation altimetry.