Pressure Converter: Pa, psi, bar, atm, mmHg & More

What is pressure?

Pressure is force per unit area—the same force spread over a smaller area gives higher pressure. The SI unit is the pascal (Pa): 1 Pa = 1 N/m² (one newton per square meter). In engineering and everyday life you’ll see bar (1 bar = 10⁵ Pa), psi (pounds per square inch, common in the US), standard atmosphere (atm) (101 325 Pa), mmHg or torr (for blood pressure and vacuum), and water-column units (inH₂O, ftH₂O). This converter supports 50+ units including SI prefixes (kPa, MPa, hPa), imperial (psi, psf, ton-force per sq in), and specialty (torr, cmHg, technical atmosphere).

Every value is normalized to pascals under the hood, so you can convert from tire pressure (psi), hydraulic specs (bar), or weather (inHg) to Pa or any other unit in one step.

How pressure conversion works

To convert between any two pressure units, we express both in pascals (Pa). Multiply your value by the source unit’s factor (how many Pa one unit equals), then divide by the target unit’s factor:

Example: convert 30 psi to bar. 1 psi ≈ 6894.76 Pa, 1 bar = 100 000 Pa, so 30 psi = 30 × 6894.76 ÷ 100 000 ≈ 2.069 bar. Another: convert 760 mmHg to atm. 760 mmHg = 101 325 Pa = 1 atm. The tool above does this for all 50+ units.

Key pressure units explained

Each unit’s factor to Pa. 1 bar = 10⁵ Pa; 1 atm = 101 325 Pa; 1 psi ≈ 6894.76 Pa; 760 mmHg = 101 325 Pa.

When to use Pa vs bar vs psi vs mmHg

Pascal (Pa) and its multiples (kPa, MPa) are the SI choice for calculations and international standards. Bar is widely used in Europe for tires, hydraulics, and process pressure (1 bar is close to 1 atm). Psi is the US customary unit for tire pressure, pressure vessels, and many datasheets. mmHg and torr are used in medicine (blood pressure), vacuum technology, and barometers. Inch of mercury (inHg) appears in US weather and aviation. Water column (inH₂O, ftH₂O, mmAq) is common in HVAC and low-pressure ductwork. This converter includes all of these so you can switch between regions and disciplines.

Who uses a pressure converter?

Mechanical and HVAC engineers convert between bar, psi, and Pa for specs and fluid systems. Medical and life sciences work with mmHg (blood pressure) and sometimes need Pa or atm. Pilots and meteorologists use inHg or hPa (hectopascal, same as millibar) for altimeter and weather. Chemical and process engineers see bar, psi, and kgf/cm² on equipment. Students and educators use it to check homework (e.g. “convert 14.7 psi to atm”) and to relate fluid mechanics formulas (in Pa) to real-world units. All conversions run in your browser—no data is sent to a server.

Why pascal is the SI unit

Pressure is force per unit area, so its dimension is force/length². In SI, force is in newtons (N) and area in m², so the coherent unit is N/m², named the pascal (Pa) after Blaise Pascal. 1 Pa = 1 N/m². The bar (100 000 Pa) and atmosphere (101 325 Pa) are accepted for use with SI but are not part of the coherent set. Using Pa keeps formulas (e.g. P = ρgh, or stress in Pa) dimensionally consistent. This converter uses Pa as the internal base so every result is traceable to SI.

Common pressure conversions at a glance

Handy reference for psi to bar, bar to Pa, mmHg to atm, and other everyday conversions.

Avoiding common mistakes

Don’t confuse absolute pressure (relative to vacuum) with gauge pressure (relative to ambient): gauge = absolute − ambient. This converter deals only with absolute pressure values; for gauge readings (e.g. tire pressure in psi), the numeric conversion is the same. Don’t mix mmHg with cmHg or inHg—they differ by factors of 10 or 25.4. “Technical atmosphere” (at, kgf/cm²) is not the same as “standard atmosphere” (atm): 1 at ≈ 98 066.5 Pa, 1 atm = 101 325 Pa. When in doubt, convert everything to Pa with this tool, then apply your formulas.

Pressure Conversion FAQ