Convert between PSI, bar, Pascal, kPa, atm, mmHg, torr and more. All results shown at once.
This free pressure converter converts between 12 pressure units simultaneously — showing every conversion at once so you don't need to repeat the process for different units. Enter any pressure value in PSI, bar, Pascal, kPa, atmospheres, mmHg, inHg, millibar, or kgf/cm² and instantly see the equivalent in all other units. Whether you're checking tire pressure specifications from a European manual (in bar) against a US gauge (in PSI), converting blood pressure readings (mmHg) to SI units (kPa) for a medical study, or checking atmospheric pressure in meteorological data (hPa) against engineering specifications (Pa), this converter handles it instantly and accurately.
All pressure units expressed in terms of their Pascal equivalent — the SI base unit of pressure. These are the exact conversion factors used by this calculator.
| Unit | Symbol | In Pascals (Pa) | System | Primary Use |
|---|---|---|---|---|
| Pascal | Pa | 1 (base unit) | SI Metric | Scientific, structural engineering |
| Hectopascal | hPa | 100 | SI Metric | Meteorology, weather forecasting (= millibar) |
| Kilopascal | kPa | 1,000 | SI Metric | Tire pressure (Canada, Australia), engineering |
| Megapascal | MPa | 1,000,000 | SI Metric | Structural engineering, material strength |
| Bar | bar | 100,000 | Non-SI Metric | Tire pressure (Europe), industrial applications |
| Millibar | mbar | 100 | Non-SI Metric | Meteorology (= hectopascal) |
| PSI | psi | 6,894.757 | US Customary | Tire pressure (USA), hydraulics, plumbing |
| Atmosphere | atm | 101,325 | Reference | Science reference point, diving, altitude |
| mmHg / Torr | mmHg | 133.322 | Historical | Blood pressure, vacuum measurement |
| Inches of Mercury | inHg | 3,386.389 | US/Aviation | Aviation altimetry, US weather reports |
| N/m² | N/m² | 1 (= Pa) | SI Metric | Engineering stress calculations |
| kgf/cm² | kgf/cm² | 98,066.5 | Technical metric | Older engineering, some hydraulic specs |
Standard atmospheric pressure at sea level (1 atm) is a fundamental reference point in pressure measurement. Here are the exact values in every common unit — useful for verifying conversions and understanding the scale of each unit.
| Unit | Standard Atmosphere Value | Notes |
|---|---|---|
| Pascal (Pa) | 101,325 Pa | Exact definition of 1 atm |
| Kilopascal (kPa) | 101.325 kPa | Most common SI atmospheric reference |
| Bar | 1.01325 bar | Just above 1 bar — why 1 bar ≈ 1 atm |
| Millibar (mbar) | 1013.25 mbar | Standard used in meteorology/weather maps |
| Hectopascal (hPa) | 1013.25 hPa | Identical to millibar — used in aviation |
| PSI | 14.6959 psi | Used in US tire and hydraulic gauges |
| mmHg | 760 mmHg | Standard reference for vacuum and blood pressure |
| Torr | 760 torr | Equivalent to mmHg by definition |
| Inches of Mercury (inHg) | 29.9213 inHg | US aviation altimeter setting, weather reports |
| kgf/cm² | 1.03323 kgf/cm² | Technical metric, older engineering specs |
Pressure is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. The SI unit is the Pascal (Pa), defined as one Newton of force per square metre of area (1 Pa = 1 N/m²). Named after Blaise Pascal, the 17th-century French mathematician and physicist who made foundational contributions to fluid mechanics, the Pascal is used across all scientific disciplines as the standard pressure unit.
Understanding the distinction between these three pressure types prevents measurement errors in engineering and industrial contexts. Absolute pressure is measured relative to a perfect vacuum (0 Pa). It gives the total pressure without any reference to atmospheric conditions. Gauge pressure is measured relative to local atmospheric pressure. A car tire gauge reads gauge pressure — a reading of 35 PSI means the tire is 35 PSI above atmospheric pressure. The absolute pressure inside the tire is 35 + 14.696 = 49.696 PSIA. Differential pressure is the difference between two pressures in a system, used in flow measurement and filter monitoring.
This distinction matters practically: if you deflate a tire to 0 PSI on a gauge, it still contains air at atmospheric pressure — the gauge reads 0 because it measures above atmospheric, not from vacuum. A true vacuum (0 PSIA) is complete absence of gas molecules.
Pascal's Law states that pressure applied to a confined fluid transmits equally in all directions throughout the fluid. This principle underpins hydraulic systems used in car brakes, construction equipment, aircraft control systems, and manufacturing presses. When you press the brake pedal in a car, you apply force to brake fluid in a master cylinder; Pascal's Law ensures that pressure is transmitted equally to all four wheel brake cylinders, multiplying force through the hydraulic piston area difference.
| Context | PSI | bar | kPa | mmHg |
|---|---|---|---|---|
| Standard atmosphere (sea level) | 14.70 | 1.013 | 101.3 | 760 |
| Car tire (typical) | 32–35 | 2.2–2.4 | 220–241 | 1,655–1,813 |
| Bicycle tire (road) | 80–130 | 5.5–9.0 | 552–896 | — |
| Mountain bike tire | 25–35 | 1.7–2.4 | 172–241 | — |
| Normal blood pressure | 2.32 / 1.55 | 0.16 / 0.11 | 16 / 10.7 | 120 / 80 |
| Household water pressure | 40–80 | 2.8–5.5 | 275–552 | — |
| Deep ocean (1000m depth) | 1,450 | 100 | 10,000 | 75,006 |
| Scuba tank (full) | 2,900–3,600 | 200–248 | 20,000–24,800 | — |
| CO₂ fire extinguisher | 850 | 58.6 | 5,861 | — |
| Perfect vacuum | 0 absolute | 0 absolute | 0 absolute | 0 absolute |
Tire pressure is specified in PSI in the United States and bar in Europe. Most modern tire pressure gauges sold in the US show PSI; European gauges show bar. A typical passenger car tire requires 30–35 PSI (2.07–2.41 bar) when cold. Under-inflated tires increase rolling resistance, reduce fuel economy, and cause uneven wear. Over-inflated tires reduce grip, cause harsh ride, and increase blowout risk. Nitrogen inflation is increasingly common in high-performance and aircraft applications because nitrogen pressure is more stable across temperature changes.
Blood pressure is universally measured in mmHg (millimeters of mercury) across all countries — one of the few areas where an outdated unit remains universal for compelling historical and practical reasons. Normal adult blood pressure is 120/80 mmHg (systolic/diastolic). Hypertension is typically defined as sustained pressure above 140/90 mmHg. Converting mmHg to kPa: normal blood pressure 120/80 mmHg = 16.0/10.7 kPa. The medical world standardised on mmHg before SI units existed, and the massive body of clinical research data in mmHg makes changing to kPa impractical.
Weather forecasting uses hectopascals (hPa) or millibars (mbar) — they're numerically identical (1 hPa = 1 mbar = 100 Pa). Standard sea level atmospheric pressure is 1013.25 hPa. Low pressure systems (below 1000 hPa) are associated with stormy weather; high pressure systems (above 1020 hPa) with fair weather. Aviation uses inches of mercury (inHg) in the US and hPa in Europe for altimeter settings — a 1 hPa change in atmospheric pressure corresponds to approximately 8 metres of altitude change.
Structural and mechanical engineers use pascals and megapascals for stress and pressure calculations. Material yield strength is specified in MPa (e.g., structural steel has a yield strength of approximately 250 MPa). Hydraulic system pressures are typically in the 14–350 bar (200–5,000 PSI) range. Gas pipeline pressures are specified in bar or kPa. The SI standard ensures unit consistency across international engineering projects.
Most passenger cars require 30–35 PSI (207–241 kPa, 2.07–2.41 bar) when cold. Find the exact specification on the door jamb sticker, in the owner's manual, or on the fuel cap. Never use the maximum pressure printed on the tire sidewall — that is the tire's structural maximum, not the correct operating pressure. Always check with the tires cold (not driven for at least 3 hours).
Divide PSI by 14.5038 to get bar. Multiply bar by 14.5038 to get PSI. Quick reference: 30 PSI = 2.07 bar, 32 PSI = 2.21 bar, 35 PSI = 2.41 bar, 40 PSI = 2.76 bar. The converter above shows all units simultaneously when you enter a value in PSI.
1 PSI = 6.89476 kPa. Multiply PSI by 6.895 to convert to kPa; divide kPa by 6.895 to convert to PSI. 35 PSI = 241 kPa. Canada, Australia, and New Zealand commonly express tire pressure in kPa rather than PSI or bar.
1 standard atmosphere = 101,325 Pa = 101.325 kPa = 1.01325 bar = 14.6959 PSI = 760 mmHg = 760 torr = 29.9213 inHg = 1013.25 hPa = 1013.25 mbar. This is the reference point for gauge pressure calculations and the baseline for weather, aviation, and scientific measurements.
Absolute pressure is measured from perfect vacuum (0 Pa absolute). Gauge pressure is measured relative to atmospheric pressure (~101.325 kPa). A tire gauge reading of 35 PSI is gauge pressure — add 14.696 PSI for absolute pressure. Most consumer gauges (tire, blood pressure, kitchen) read gauge pressure unless marked "absolute" or "PSIA".
Historical standard — early blood pressure instruments used mercury columns. The clinical world has maintained mmHg for over a century of reference data. Normal blood pressure is 120/80 mmHg = 16.0/10.7 kPa. Changing to SI units would make existing clinical guidelines and decades of research data difficult to apply without constant conversion.
The Pascal is the SI unit of pressure: 1 Pa = 1 N/m². It's very small — atmospheric pressure is 101,325 Pa. Used in scientific research, structural engineering (wind loads, material stress), acoustics (sound pressure: 20 μPa threshold of hearing, 20 Pa threshold of pain), and as the base for all other SI-derived pressure units (kPa, MPa, hPa).
1 bar = 14.5038 PSI. 1 bar is approximately equal to 1 atmosphere (actually 1 atm = 1.01325 bar). European tire specifications commonly use 2.0–2.5 bar for passenger cars. The bar is widely used in European and international industry as a practical near-atmospheric pressure unit.
Torr is named after Evangelista Torricelli and equals 1/760 of a standard atmosphere. For practical purposes, 1 torr = 1 mmHg (they differ by only 0.000015%). Torr is used in vacuum science and laboratory settings; mmHg is used in medical blood pressure measurement. Both equal 133.322 Pa.
USA: PSI for tires, hydraulics, and most engineering. Europe: bar for tires and industrial use; kPa and Pa in science. UK: PSI and bar both common for automotive; kPa in science. Worldwide: Pa/kPa in scientific and engineering contexts; mmHg in medicine; hPa/mbar in meteorology; inHg in US aviation.