Pressure Converter: Pa, bar, psi, atm, mmHg and Torr
What the pressure converter does The pressure converter changes one value between the ten units that cover weather, medicine, engineering and diving: pascal (Pa), kilopascal (kPa), megapascal (MPa), bar, millibar (mbar), pound per square inch (psi), standard atmosphere (atm), millimeter of mercury (mmHg), torr (Torr) and inch of mercury (inHg). Type on either card and the other card and the All Units list update as you type; nothing leaves the browser.
The units share a quantity but not an ancestry: the SI pascal, the laboratory's mercury column, the weather map's bar and the workshop's psi. The trap is that bar, atm and psi all sit near one atmosphere but are not interchangeable numbers.
How to use it 01 Pick the unit you have on the left card and the unit you want on the right; both dropdowns list the same ten units, starting on Pa → kPa. 02 Type a value on either side. The other side converts as you type, and All Units repeats the value in every unit at once. 03 The focused field also takes expressions: 18+14 shows a quiet = 32 hint and converts live; Enter or = settles the entry to 32. 04 Press the swap button to exchange the two chosen units and carry the value across. 05 Click any All Units row to move that unit to the focused card, and open the keypad for a side calculation without leaving the page. Worked examples Every readout below is exactly what this tool displays.
Setup
Readout
1 bar → psi
14.503773773 psi
1 atm → psi
14.6959487755 psi
1 psi → Pa
6,894.75729317 Pa
32 psi → bar
2.2063223338 bar
1,013.25 mbar → atm
1 atm
1 atm → mmHg
759.999891726 mmHg
1 atm → Torr
760 Torr
1 mmHg → Torr
1.0000001425 Torr
120 mmHg → kPa
15.9986864898 kPa
Two rows are exact by definition: 1,013.25 mbar = 101,325 Pa = 1 atm, and the torr is 101,325/760 Pa. The mmHg row stops at 759.999891726 because a conventional millimeter of mercury (133.322387415 Pa) is a slightly larger unit than the torr. Expressions work too: 18+14 typed on the bar card reads 464.120760737 psi while the hint shows = 32, and Enter settles the bar entry to 32 .
Where the units come from The pascal is one newton per square meter, the SI derived unit of pressure; kPa and MPa are its 10³ and 10⁶ multiples. The bar is exactly 100,000 Pa and the millibar exactly 100 Pa, which makes the weather service's hectopascal identical to a millibar. The standard atmosphere is fixed at exactly 101,325 Pa.
The mercury units come from barometers: a conventional millimeter of mercury is a 1 mm column of density 13,595.1 kg/m³ under standard gravity 9.80665 m/s², or 133.322387415 Pa, and an inch of mercury is 25.4 of those. The torr, named for Torricelli, is defined separately as 101,325/760 Pa = 133.322368421… Pa — smaller than a mmHg by about one part in seven million, a difference the converter keeps. The psi descends from the 1959 international yard and pound: one pound-force (0.45359237 kg × 9.80665 m/s²) over one square inch (0.0254 m)² gives 1 psi = 6,894.757293168361… Pa exactly, which the tool rounds to 6,894.75729317 Pa on screen.
Limits and what it does not do
Display precision. Readouts carry 12 significant digits: values from 10⁻¹⁰ up to but not including 10¹⁵ print with comma grouping and at most 10 decimal places, and anything smaller or larger uses exponential form with six decimals. 1 Pa → psi reads 0.0001450377 , and 10⁻¹¹ Pa reads 1.000000e-11 . No pressure physics. Force from pressure × area, gas-law relationships and pressure × volume work are outside a unit conversion. Enter those formulas in the scientific calculator ; when the follow-up quantity is work or rate, the energy converter and the power converter carry it on. Common mistakes
bar, atm and psi are not synonyms. 1 bar reads 14.503773773 psi , 1 atm reads 14.6959487755 psi — about 1.3% apart. Use the unit named on the gauge or the document.Tyre and gas-line figures are usually gauge pressure. A gauge reading 32 psi means 32 psi above ambient, about 46.6959487755 psi absolute at standard sea level (32 + 14.6959487755). This converter has no psig/psia switch.mmHg and Torr diverge in the seventh digit. 1 mmHg is 1.0000001425 Torr ; 760 Torr is exactly 1 atm, while 760 mmHg is 1.0000001425 atm .Weather maps say hPa. The list has mbar, not hPa, but they are the same size: 1 hPa = 1 mbar = 100 Pa, so 1,013.25 hPa is the standard atmosphere. Where it fits Tyres and workshop air A placard reading 2.2 bar is 31.9083023006 psi ; a gauge reading 32 psi is 2.2063223338 bar . The two numbers describe the same tyre pressure within about 0.3%.
Weather and aviation A surface analysis at 1,013.25 mbar is exactly one standard atmosphere; the same value in the inHg row is 29.9212555797 inHg , the mercury-inch figure used in US aviation settings.
Medicine and the laboratory A blood pressure of 120/80 mmHg converts to 15.9986864898 kPa (systolic) and 10.6657909932 kPa (diastolic); vacuum readings quoted in torr land in pascals and millibars in the same table.
Privacy All input and calculation run inside your browser and are never uploaded; this page is static text and records no user input.
References
BIPM, The International System of Units (SI Brochure) , 9th edition — the pascal as newtons per square metre and the SI prefixes. bipm.org （访问日期：2026-09-30）
NIST Special Publication 811, Appendix B.8, Factors for Units Listed Alphabetically — the exact standard atmosphere (1.013 25 E+05 Pa), bar, millibar, psi and the conventional mercury units. nist.gov （访问日期：2026-09-30）
Wikipedia, Pound per square inch — 1 lbf/in² = 8896443230521/1290320000 Pa, and the psia/psig distinction. en.wikipedia.org （访问日期：2026-09-30）
Wikipedia, Millimetre of mercury — the conventional 13,595.1 kg/m³ column and how it differs from the torr. en.wikipedia.org （访问日期：2026-09-30）
Wikipedia, Pressure measurement — absolute, gauge and differential references behind the gauge caveat. en.wikipedia.org （访问日期：2026-09-30）
Sources & review
Reviewed by CalcX Editorial Team
Updated 2026-09-30 BIPM, The International System of Units (SI Brochure), 9th edition — the pascal as newtons per square metre and the SI prefixes (accessed 2026-09-30) NIST Special Publication 811, Appendix B.8, Factors for Units Listed Alphabetically — exact factors for the standard atmosphere, bar, millibar, psi and the conventional mercury units (accessed 2026-09-30) Wikipedia, Pound per square inch — 1 lbf/in² = 8896443230521/1290320000 Pa, and the psia/psig distinction (accessed 2026-09-30) Wikipedia, Millimetre of mercury — the conventional 13595.1 kg/m³ column and how it differs from the torr (accessed 2026-09-30) Wikipedia, Pressure measurement — absolute, gauge and differential references for the gauge caveat (accessed 2026-09-30)