Convert between pascals, kilopascals, bar, psi, atmospheres, torr, mmHg, kgf/cm² and more, a full unit table, and conversion history.
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Founder & CEO, Toolraxy
Faiq Ur Rahman is a web designer, digital product developer, and founder of Toolraxy, a growing platform of web-based calculators and utility tools. He specializes in building structured, user-friendly tools focused on health, finance, productivity, and everyday problem-solving.
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Pressure unit conversion is the process of expressing the same physical quantity in a different unit of measurement. One bar equals 100,000 pascals, one pound per square inch equals 6,894.757293168 pascals, and every conversion routes through the pascal because it is the SI derived unit of pressure, defined by the International Bureau of Weights and Measures as one newton per square metre.
In practice, a hydraulic technician in the US reads a gauge in psi while the German machine manual specifies 250 bar. A weather observer logs 1013.25 hPa while an aviation altimeter is set in inHg. A materials engineer tests a concrete cylinder at 30 MPa while the client’s specification is in kgf/cm². The math is simple multiplication, but the unit mismatch is constant. In 1999, NASA lost the Mars Climate Orbiter partly because a navigation model expected pressure and force values in SI units but received data in pound-force and pound-per-square-inch units. The spacecraft entered the Martian atmosphere at the wrong altitude and was destroyed. The converter removes that risk by routing everything through pascals and showing every equivalent at once.
You convert pressure units by multiplying the input value by the source unit’s pascal factor, then dividing by the target unit’s pascal factor. The converter handles this automatically: type a number, select the from unit and to unit, and the result recalculates on every keystroke. The unit label beside the input field confirms which unit you’re entering.
Select the from unit: the unit your input value is currently expressed in. The dropdown groups options by system: Metric / SI, Bar & Atmosphere, Mercury / Water, Imperial / US, and Other.
Select the to unit: the unit you want the result in. The converter defaults to bar → psi, but you can pick any pair from the 18 supported units.
Enter the pressure value in the input field. The unit label beside the field updates automatically to match your from-unit selection.
Read the hero result: the large number at the top of the results panel shows the converted value with your chosen precision.
Check the full unit table below the hero result to see the same pressure expressed in all 18 units simultaneously.
Adjust decimal places using the 2 / 4 / 6 / 8 / 10 segmented control if you need more or fewer digits.
Press Enter or click away to save the result to the history table. The converter also records a history entry when you change units after entering a value.
The formula converts any pressure unit to any other pressure unit through the pascal as the base. Each unit has a fixed multiplier that expresses one unit of that pressure in pascals.
Formula: Result = Input value × (Source unit’s pascal factor) ÷ (Target unit’s pascal factor)
The pascal factor for each unit is fixed by definition. The bar factor, 100,000 Pa, is exact by definition in the SI system. The psi factor, 6,894.757293168 Pa, derives from the pound-force and the square inch. The standard atmosphere factor, 101,325 Pa, was defined by the 10th General Conference on Weights and Measures in 1954. The torr is defined as exactly 1/760 of a standard atmosphere, which works out to 133.32236842105263 Pa. These factors are exact, not approximations, and the tool uses full precision internally before formatting the displayed result.
The converter supports all 18 units shown in the dropdown. Unit switching happens through the dropdown selectors, not through separate input fields. If you change the from unit after entering a value, the tool treats the same number as a value in the new unit and recalculates.
Suppose you’re commissioning a hydraulic press built to a US specification of 3,000 psi, and the European machine controller expects pressure in bar and MPa. You need to confirm the setpoints.
Step 1. Select psi as the from unit and bar as the to unit.
Step 2. Enter 3000 in the value field.
Step 3. The converter multiplies 3,000 by 6,894.757293168 (the psi pascal factor), giving 20,684,271.88 Pa.
Step 4. It divides 20,684,271.88 by 100,000 (the bar pascal factor), giving 206.84 bar.
Step 5. Switch the to unit to MPa. The same pressure reads 20.68 MPa.
Step 6. The full unit table shows the same pressure as 20,684,271.88 Pa, 206.84 bar, 20.68 MPa, 204.14 atm, and 210.92 kgf/cm².
The result tells you the European controller needs a setpoint of 206.8 bar or 20.68 MPa to match the US specification of 3,000 psi. If the machine’s relief valve is rated at 210 bar, the margin is only 1.5%, which is tight for a hydraulic system. Most hydraulic circuits run a 10–20% margin between working pressure and relief setting. The conversion reveals that this system needs a relief valve rated at 230 bar or higher to maintain a safe margin.
This table lists the pascal factor for every unit the converter supports. Multiply any value in a given unit by its factor to get pascals, then divide by the target unit’s factor to get the converted value. These factors are exact definitions, not rounded approximations, and the tool uses them at full precision.
| Unit | Pascal Factor (1 unit = X pascals) |
|---|---|
| Pascal (Pa) | 1 |
| Hectopascal (hPa) | 100 |
| Kilopascal (kPa) | 1,000 |
| Megapascal (MPa) | 1,000,000 |
| Newton per mm² (N/mm²) | 1,000,000 |
| Bar (bar) | 100,000 |
| Millibar (mbar) | 100 |
| Standard atmosphere (atm) | 101,325 |
| Technical atmosphere (at) | 98,066.5 |
| Torr (torr) | 133.32236842105263 |
| Millimeter of mercury (mmHg) | 133.322387415 |
| Inch of mercury (inHg) | 3,386.389 |
| Inch of water (inH2O) | 249.08890833333 |
| Foot of water (ftH2O) | 2,989.0669 |
| Pound per square inch (psi) | 6,894.757293168 |
| Pound per square foot (psf) | 47.88025898033584 |
| Kilogram-force per cm² (kgf/cm²) | 98,066.5 |
| Dyne per cm² (dyn/cm²) | 0.1 |
This table lists typical pressure ranges for the applications where pressure unit conversion comes up most often. The values are drawn from published engineering references and industry practice. They are not tool outputs; they are context for interpreting what a converted number means.
| Application | Typical Pressure Range |
|---|---|
| Atmospheric pressure at sea level | 101,325 Pa / 1,013.25 hPa / 1 atm / 14.696 psi |
| Weather reporting (surface) | 980–1,040 hPa, varies with weather systems |
| Automotive tire pressure (passenger car) | 30–35 psi / 2.07–2.41 bar |
| Automotive tire pressure (truck) | 80–120 psi / 5.5–8.3 bar |
| Residential natural gas supply | 0.25–0.5 psi / 6.9–13.8 inH2O |
| Residential water supply | 40–80 psi / 2.76–5.52 bar |
| Hydraulic systems (industrial) | 1,000–5,000 psi / 69–345 bar |
| Scuba tank (full) | 3,000–3,500 psi / 207–241 bar |
| Medical oxygen cylinder (full) | 2,000–2,200 psi / 138–152 bar |
| Compressed air (shop tools) | 90–150 psi / 6.2–10.3 bar |
| Boiler steam (industrial) | 100–900 psi / 6.9–62 bar |
| Concrete compressive strength | 20–50 MPa / 2,900–7,250 psi |
| Vacuum (rough) | 1–1,000 Pa / 0.01–10 mbar |
| Vacuum (high) | 10⁻³–10⁻⁷ Pa / 10⁻⁵–10⁻⁹ mbar |
The pascal became the SI derived unit of pressure in 1971, when the General Conference on Weights and Measures adopted it as part of the International System of Units. The unit is named after Blaise Pascal, the 17th-century French mathematician and physicist who studied fluid pressure and contributed to the development of the hydraulic press. One pascal is the pressure exerted by one newton of force applied uniformly over one square metre. The International Bureau of Weights and Measures maintains this definition in the SI Brochure.
Before the pascal, engineers worked in a wide range of pressure units: bar in European industry, psi in the English-speaking world, atmosphere as a reference for weather, and mercury column units for medical and vacuum measurements. These units developed independently because pressure measurement evolved differently in different fields. Bar came from the Greek word for weight and was defined as 1,000,000 dynes per square centimetre, which equals 100,000 pascals. psi came from the pound-force and the square inch, the two fundamental units of the imperial system. Atmosphere came from the average pressure of the Earth’s atmosphere at sea level.
The pascal solved the coherence problem: it derives directly from the newton and the square metre, which derive from the kilogram, metre, and second. Energy (joule), power (watt), and force (newton) all fit together without conversion factors. That coherence is why the pascal became the global standard, even though bar and psi remain in daily use in many industries.
The transition took decades and remains incomplete. The UK began metrication in 1965 and adopted the pascal for most engineering work, but tire pressure in the UK is still commonly quoted in psi. US engineering standards still list psi as the primary unit for hydraulic and pneumatic work, though most software tools support both. The National Institute of Standards and Technology lists the conversion factors between the pascal and non-SI units in its guide to the SI, and those factors are exact by definition, not measured approximations.
Multiply the bar value by 14.503773773. For example, 2 bar × 14.504 = 29.01 psi. The converter does this instantly when you select bar as the from unit and psi as the to unit.
One bar equals exactly 100 kilopascals. The bar is defined as 100,000 pascals, and one kilopascal is 1,000 pascals, so 1 bar = 100 kPa. This is one of the cleanest conversions in the pressure system.
One standard atmosphere equals 14.6959487755 psi. The standard atmosphere is defined as exactly 101,325 Pa, and psi is 6,894.757293168 Pa, so 101,325 ÷ 6,894.757 = 14.696 psi.
One atmosphere equals 1.01325 bar. The bar is a metric unit defined as exactly 100,000 Pa; the standard atmosphere is defined as exactly 101,325 Pa. They’re close, but not identical. A 1-bar reading is about 1.3% lower than 1 atm.
No. psi is a unit of pressure. psia means pounds per square inch absolute, measured from a perfect vacuum. psig means pounds per square inch gauge, measured from atmospheric pressure. At sea level, 0 psig = 14.696 psia. The converter converts the number, not the reference.
Multiply the mmHg value by 0.133322387415. One mmHg equals approximately 0.1333 kPa. For example, 760 mmHg (standard atmospheric pressure) equals 101.325 kPa.
One kgf/cm² equals 0.980665 bar. The two units are close enough that they’re sometimes confused, but the difference is about 2%. In high-pressure systems, that 2% can matter. The exact factor is 98,066.5 Pa per kgf/cm².
Yes. The converter accepts negative inputs and returns negative results. Negative pressure values typically indicate vacuum (pressure below a reference) or a sign convention in a calculation. The tool converts the number the same way regardless of sign.
The conversion is mathematically exact for the unit definitions used. The displayed result is rounded to your chosen decimal places, but the underlying calculation runs at full precision. Any inaccuracy comes from the input value’s precision, not the conversion itself.
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