AkCalculators

Pressure Converter — a practical guide to pressure units and conversions

Pressure is a fundamental physical quantity used in many fields: meteorology, fluid mechanics, hydraulics, HVAC, material testing and more. Different industries and regions prefer different units, which makes quick and accurate unit conversion essential. This Pressure Converter converts between SI and common engineering units — Pascals (Pa), kilopascals (kPa), megapascals (MPa), bar, atmosphere (atm), psi, torr, mmHg, inHg and kilogram-force per square centimeter (kgf/cm²).

What is pressure?

Pressure is force per unit area. In SI units, pressure is expressed in Pascals (Pa), where 1 Pa = 1 N/m² (one newton per square meter). Since many pressures are much larger than a single Pascal, we commonly use derived units like kilopascal (kPa) and megapascal (MPa) or non-SI units such as bar and psi.

Common pressure units and when to use them

• Pascal (Pa) — SI unit, used in scientific calculations. 1 Pa = 1 N/m².
• Kilopascal (kPa) — 1 kPa = 1,000 Pa. Frequently used in engineering and meteorology (e.g., atmospheric pressure ~101.325 kPa).
• Megapascal (MPa) — 1 MPa = 1,000,000 Pa. Common in material testing and hydraulic systems.
• Bar — 1 bar = 100,000 Pa. Widely used in meteorology and tire pressure (bar is convenient close to atmospheric pressure).
• Atmosphere (atm) — 1 atm = 101,325 Pa. Standard reference for atmospheric pressure at sea level.
• PSI (pound-force per square inch) — Imperial unit used in the US, especially for tires, hydraulics, and pressure gauges. 1 psi ≈ 6,894.757 Pa.
• Torr and mmHg — 1 torr ≈ 133.322368 Pa; 1 mmHg ≈ 133.322387 Pa. Used in vacuum science and medical contexts for blood pressure (often mmHg).
• inHg — inches of mercury; used in weather reports and aviation altimeters in some regions (1 inHg ≈ 3,386.388 Pa).
• kgf/cm² (kilogram-force per cm²) — Common in some engineering contexts (1 kgf/cm² ≈ 98,066.5 Pa).

Canonical conversion method

This converter uses Pascal (Pa) as the internal canonical unit. The conversion process is:

1. Multiply the input by the “Pa-per-unit” factor to get Pascals.
2. Divide Pascals by the “Pa-per-target” factor to get the target unit.

This ensures conversions are simple, robust and accurate across the supported units.

Key conversion factors (quick reference)

Worked examples — practical scenarios

Example 1 — Tire pressure: A car tyre reads 32 psi. Convert to kPa.

32 psi × 6,894.757293168 Pa/psi = 220,632.23 Pa = 220.632 kPa (approx.).

Example 2 — Atmospheric pressure: Sea-level atmospheric pressure ~1 atm = 101,325 Pa = 101.325 kPa = 1.01325 bar.

Example 3 — Hydraulic pressure: A hydraulic press operates at 50 MPa. Convert to psi for a US datasheet.

50 MPa × (1,000,000 Pa / MPa) ÷ 6,894.757293168 ≈ 7,251.54 psi.

Example 4 — Medical: Normal blood pressure is often quoted as 120/80 mmHg. Convert 120 mmHg to kPa.

120 mmHg × 133.322387415 Pa/mmHg = 15,998.6865 Pa ≈ 15.999 kPa.

When to use which unit (industry guidance)

• Meteorology: kPa or hPa (hectopascal, 1 hPa = 100 Pa) — many weather services report pressure in hPa.
• Automotive: psi for tire pressure (US), bar in many other countries.
• Hydraulics & material testing: MPa for high pressures.
• Vacuum & laboratory: torr and mmHg in vacuum science; Pa and mbar are also common.
• Aviation: inHg in the US for altimeter settings; hPa elsewhere.

Best practices & common mistakes

• Mind units shown on instruments: Don’t assume the gauge reads psi or bar — check the label.
• Watch significant figures: Match the precision of input values — don’t report unrealistic precision from rough gauges.
• Use consistent reference temperature for fluids: For high-precision work, pressure can be temperature-dependent due to fluid properties and sensor calibration.
• Convert through Pascals: Using the canonical Pa avoids chaining mistakes when converting between obscure units.

How this converter helps engineers and technicians

The tool is useful for quickly translating pressure values between international standards and local practices: converting bar to psi for a US datasheet, translating mmHg to kPa in medical contexts, or checking atmospheric pressure readings for weather or altimeter calibration.

FAQ

Conclusion

This Pressure Converter gives fast, accurate conversions across the units most commonly used in science and industry. Keep it bookmarked when comparing sensor data, writing technical reports, configuring equipment, or translating documentation between regions.