PSI Pressure Converter

About the PSI Pressure Converter

Pounds per square inch (PSI) is the most widely used pressure unit in US engineering, from tire pressures and hydraulic systems to scuba tank ratings and blood pressure. Converting between PSI, kPa, bar, atmosphere, mmHg, and other units is a daily task in engineering and science.

This comprehensive converter handles all common pressure units: PSI, kPa, MPa, bar, atm, mmHg (Torr), inHg, inH₂O, and millibar. Enter a value in any unit and review the equivalent in all others. It also computes the force exerted on a given area and the equivalent water column depth.

Preset buttons load common reference pressures: tire pressure (32 PSI), scuba tank (3000 PSI), hydraulic system (5000 PSI), standard atmosphere (14.696 PSI), 1 bar, and blood pressure (120 mmHg). A conversion table provides quick lookups for common values.

The calculator is essential for mechanical engineers, HVAC technicians, medical professionals, divers, and anyone working with pressure measurements in mixed US/metric environments.

When This Page Helps

Pressure unit conversion errors between US customary (PSI) and SI (kPa, bar) are among the most common engineering mistakes. This converter shows all units simultaneously.

The force-on-area calculation is invaluable for seal design, cylinder sizing, and load analysis. Seeing the conversions side by side makes it easier to spot when a number is gauge pressure, absolute pressure, or just a rounded reference value.

How to Use the Inputs

1. Select the input pressure unit from the dropdown.
2. Enter the pressure value.
3. Optionally enter an area (cm²) for force calculation.
4. Read the pressure in all common units simultaneously.
5. Use presets for common reference pressures.
6. Check the conversion table for quick lookups.

Example Calculation

Tips & Best Practices

• 1 atm ≈ 15 PSI ≈ 100 kPa ≈ 1 bar ≈ 760 mmHg — memorize these round approximations.
• Tire pressures are gauge (PSIG). Tank pressures may be absolute (PSIA) — always check.
• Water column: 1 PSI ≈ 2.31 feet or 0.703 m of water head.
• For quick PSI → bar: divide by 14.5. For PSI → kPa: multiply by 6.9.
• Blood pressure uses mmHg by medical convention, even though electronic monitors measure kPa internally.

Pressure Scales

PSI is a convenient working unit in mechanical systems, but it is only one point on a wider scale that includes bar, atm, kPa, mmHg, and head-pressure units. Converting between them helps when a spec sheet, gauge, and control system do not use the same unit.

Gauge Versus Absolute

The most common mistake is mixing PSI gauge and PSI absolute. Gauge pressure is relative to atmosphere; absolute pressure includes atmosphere. The conversion table and reference notes in this calculator are meant to make that distinction visible before the number is used in a design or report.

Practical Use

Use this calculator when checking tire pressure, hydraulic pressure, or medical and meteorological values that are reported in different unit systems. The extra force and water-head outputs help translate the pressure into a physical quantity people can sanity-check.

Frequently Asked Questions

• What is the difference between PSI and PSIA/PSIG?

  PSIA is absolute pressure (including atmospheric). PSIG is gauge pressure (relative to atmosphere). PSIA = PSIG + 14.696. A tire at 32 PSIG is 46.7 PSIA.

• When is mmHg used?

  mmHg (also called Torr) is used for blood pressure, vacuum systems, and meteorology. Normal blood pressure is 120/80 mmHg = 15.9/10.6 kPa.

• Is bar the same as atmosphere?

  Almost but not quite. 1 bar = 100 kPa, while 1 atm = 101.325 kPa. The difference is about 1.3%. In practice, they are often treated as equivalent for rough calculations.

• What pressure units do divers use?

  Divers use bars or PSI for tank pressure, and atmospheres (ATA) for depth pressure. Every 10 meters of seawater adds about 1 atmosphere (14.7 PSI).

• How do I convert weather pressure?

  Weather reports use millibars (hPa) or inHg. Standard: 1013.25 mbar = 29.92 inHg = 14.696 PSI. Low pressure (storm): ~980 mbar. High pressure: ~1030 mbar.

• What is the highest pressure used industrially?

  Ultra-high pressure water jets operate at 60,000-90,000 PSI (4,000-6,000 bar). Diamond anvil cells in research reach millions of PSI.