Pressure Unit Converter

About the Pressure Unit Converter

Pressure is one of the most over-unitized quantities in science and engineering. Between Pascals, PSI, bar, atmospheres, mmHg, inches of mercury, centimeters of water, and technical atmospheres, even experienced engineers occasionally need to look up conversion factors. Different industries stubbornly prefer their own units — HVAC uses inches of water for duct pressure, tire shops use PSI, meteorologists use hectopascals, and hydraulics engineers use bar or MPa.

This converter supports 13 pressure units with instantaneous cross-conversion. Enter a value in any unit and see all 13 equivalents at once, plus a real-world context indicator that tells you where your pressure sits on the scale from perfect vacuum to diamond anvil cell. Batch conversion handles bulk datasets, and the context table gives intuitive scale for pressures from weather systems to industrial hydraulics.

Whether you're checking tire pressure, calibrating sensors, converting lab data, or translating between US customary and SI units, this converter covers every pressure unit you'll encounter in practice.

When This Page Helps

Use this converter when you need to move between pressure units that belong to different industries, not just different number scales. It is helpful for translating sensor data, HVAC readings, tire pressures, lab measurements, and barometric values without having to remember which units are gauge-oriented, water-column based, or tied to older conventions.

How to Use the Inputs

1. Select your input pressure unit from 13 available options.
2. Enter the pressure value, or click a preset for common reference points.
3. Select your target output unit.
4. Read the primary conversion and all 13 unit equivalents in the table.
5. Check the context indicator to understand where your pressure falls on the real-world scale.
6. Use the batch conversion section for converting multiple values at once.
7. Consult the pressure contexts table for common engineering reference points.

Example Calculation

Tips & Best Practices

• Tire pressure gauges read in PSIG (gauge). Add 14.7 PSI for absolute pressure.
• Blood pressure is given in mmHg: 120/80 mmHg ≈ 16/10.7 kPa.
• For HVAC duct pressures, use inches of water (inH₂O) — typical static pressure is 0.5–2 inH₂O.
• Scuba diving adds about 1 atm per 10 meters of water depth.
• When in doubt, convert to Pascals first — it is the SI base unit and eliminates ambiguity.

Common Pressure Unit Families

**SI family**: Pa, hPa, kPa, MPa, GPa — related by powers of 10. Used in science, engineering, and internationally.

**US customary**: PSI (PSIA for absolute, PSIG for gauge) — dominant in US automotive, HVAC, and industrial applications.

**Barometric**: mbar/hPa (meteorology), mmHg/Torr (medicine, vacuum), inHg (US weather reports, aviation).

**Water column**: cmH₂O, inH₂O — used in HVAC, respiratory medicine, and low-pressure measurement.

Gauge vs Absolute Pressure

Pressure instruments may read "gauge pressure" (relative to atmospheric) or "absolute pressure" (relative to perfect vacuum). At sea level, absolute = gauge + 101,325 Pa (≈14.7 PSI). Always clarify which reference is used — mixing them up is a common and dangerous error in engineering.

Historical Units

The Torr was named after Evangelista Torricelli, who invented the mercury barometer in 1643. The atmosphere was originally defined as the pressure needed to support 760 mm of mercury. Modern definitions are based on the Pascal (1 N/m²), named after Blaise Pascal, who demonstrated atmospheric pressure with his famous barrel experiment.

Frequently Asked Questions

• What is standard atmospheric pressure?

  1 atm = 101,325 Pa = 14.696 PSI = 1.01325 bar = 760 mmHg = 29.92 inHg. This is defined as sea-level pressure at 15 °C.

• What is the difference between PSI and PSIG?

  PSI is absolute pressure; PSIG (PSI gauge) is pressure above atmospheric. A tire at 32 PSIG is 32 + 14.7 = 46.7 PSIA.

• Why do meteorologists use hectopascals?

  Hectopascals (hPa) are numerically identical to millibars (mbar), which meteorology has used since the mid-20th century. 1 hPa = 100 Pa = 1 mbar.

• What is mmHg used for?

  mmHg (millimeters of mercury) is traditional in blood pressure readings, vacuum systems, and barometers. 1 mmHg ≈ 1 Torr.

• What is kg/cm² (technical atmosphere)?

  A technical atmosphere (at) equals the pressure of 1 kgf per cm². It is 98,066.5 Pa — close to, but not equal to, a standard atmosphere (101,325 Pa).

• Is bar the same as atmosphere?

  Nearly — 1 bar = 100,000 Pa while 1 atm = 101,325 Pa. The difference is about 1.3%, but it matters in precise work.