Convert pressure quantities instantly across Pa, kPa, MPa, bar, psi, atm, and Torr/mmHg with exact NIST coefficients and water column depth equivalents.
Scientific & Industrial Pressure Milestones
🎯 Estimate-First Engineering Challenge
Before peeking below, can you estimate how many Kilopascals (kPa) equal 32 psi?
Target (Kilopascals)
220.632233
Hydrostatic Water Column Head
22.4982 mH₂O
Equivalent vertical depth in standard freshwater
Logarithmic Magnitude (Pascals)220,632.233 Pa
100 Pa10 kPa1 MPa100 MPa
Simultaneous 7-Unit Equivalency Matrix
Pascals (Pa)
220,632.23338
Kilopascals (kPa)
220.63223
Megapascals (MPa)
0.22063
Bars (bar)
2.20632
Pounds per Sq Inch (psi)
32
Standard Atmospheres (atm)
2.17747
Torr / mmHg (Torr)
1,654.87784
Step-by-Step Mathematical Walkthrough
Step 1: Convert source unit to Pascals (Pa)
Pascals = 32 psi × 6,894.757293168 = 220,632.233381 Pa
Step 2: Convert Pascals to target unit (Kilopascals)
Kilopascals = 220,632.233381 Pa / 1,000 = 220.632233 kPa
Step 3: Hydrostatic Water Column Head Equivalent (mH₂O)
h = 220,632.233381 Pa / (1,000 kg/m³ × 9.80665 m/s²) = 22.4982 meters of standard freshwater
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About the Pressure Converter
Pressure is defined as force distributed over an area, and it appears in nearly every branch of engineering, meteorology, medicine and industry. The SI derived unit is the pascal, equal to one newton per square metre, but the pascal is inconveniently small for everyday use — ordinary atmospheric pressure is about 101,325 of them — so a thicket of practical units grew up around it. Meteorologists use hectopascals and millibars, automotive and plumbing trades use pounds per square inch, medicine measures blood pressure in millimetres of mercury, vacuum work uses torr, and process engineering favours bar and megapascals. Because these units come from different traditions rather than a single coherent system, converting between them accurately matters: a misread tyre pressure or a confused gauge-versus-absolute reading can be a safety issue rather than an academic one. Every factor used by this converter is an exact defined value or an internationally fixed conversion, not an approximation.
Mathematical Formula & Logic
Pressure is force per unit area, converted through a common base of pascals.
1. Definition:
P = F / A
Where F is force in newtons and A is area in square metres.
1 pascal (Pa) = 1 newton per square metre = 1 kg·m⁻¹·s⁻²
2. Conversion method:
value_in_pascals = input × factor(from_unit)
result = value_in_pascals ÷ factor(to_unit)
3. Exact conversion factors to pascals:
1 kPa = 1,000 Pa (exact, SI prefix)
1 MPa = 1,000,000 Pa (exact, SI prefix)
1 bar = 100,000 Pa (exact by definition)
1 atm = 101,325 Pa (exact by definition)
1 psi = 6,894.757293168 Pa (from exact lbf and inch definitions)
1 torr = 101,325 / 760 Pa
≈ 133.322368 Pa (exact as a ratio)
4. Gauge versus absolute pressure:
P_absolute = P_gauge + P_atmospheric
Tyre and boiler gauges read zero at ambient pressure, so a gauge
reading of 32 psi corresponds to roughly 46.7 psi absolute at sea level.
Step-by-Step Example
Convert a car tyre pressure of 32 psi into kilopascals and bar:
1. Identify the source factor: 1 psi = 6,894.757293168 Pa.
2. Convert the input to the base unit:
32 × 6,894.757293168 = 220,632.233 Pa
3. Convert pascals to kilopascals by dividing by the kPa factor of 1,000:
220,632.233 ÷ 1,000 = 220.632 kPa
4. Convert pascals to bar by dividing by the bar factor of 100,000:
220,632.233 ÷ 100,000 = 2.206 bar
5. Result: 32 psi = 220.63 kPa = 2.21 bar.
Remember that this is gauge pressure, which is what a tyre gauge displays. The absolute pressure inside the tyre is 220,632 + 101,325 = 321,957 Pa, or about 322 kPa, because the gauge subtracts the surrounding atmosphere. Tyre placards and pump displays always mean gauge pressure.
Reference Data & Values
unit
pascals
typical use
Pascal (Pa)
1
SI base for pressure; scientific work
Kilopascal (kPa)
1,000
Tyre pressure and weather outside the US
Megapascal (MPa)
1,000,000
Material strength, hydraulics
Bar
100,000
Process engineering, diving, espresso machines
PSI
6,894.757293168
US tyre, plumbing and compressor gauges
Standard atmosphere (atm)
101,325
Chemistry reference conditions
Torr / mmHg
133.322368
Blood pressure, vacuum systems
Frequently Asked Questions
Absolute pressure is measured from a perfect vacuum, while gauge pressure is measured relative to the surrounding atmosphere and therefore reads zero when a vessel is open to the air. The relationship is P_absolute = P_gauge + P_atmospheric, so a tyre showing 32 psi on the gauge actually contains about 46.7 psi absolute at sea level. Units are sometimes disambiguated as psig and psia. This distinction is critical in thermodynamics and gas-law calculations, which require absolute values, and mixing the two is one of the most common errors in engineering coursework.
They are the same to within about one part in seven million, close enough that the two are used interchangeably in almost all practical work. The torr is defined exactly as 1/760 of a standard atmosphere, which is 101,325/760 pascals, whereas the conventional millimetre of mercury is defined as 133.322387415 pascals based on the density of mercury under standard gravity. The tiny gap arises because the two definitions were fixed independently. This converter uses the exact torr ratio.
The bar was chosen for convenience rather than derived from the SI base units, being defined as exactly 100,000 pascals simply because that lands very close to average atmospheric pressure at sea level. The International Bureau of Weights and Measures accepts it for use alongside SI but does not include it in the system proper, since coherent SI derived units must follow from the base units without arbitrary numerical factors. Its practicality keeps it firmly in use across European process industries and in diving.
Pounds per square inch is embedded in an enormous installed base of gauges, fittings, pipe standards and safety codes that would be expensive and hazardous to relabel piecemeal. Because pressure ratings are stamped into physical equipment and written into regulations, changing the unit means recertifying hardware rather than just editing documents. The result is a stable split in which US tyre and plumbing work stays in psi while scientific and medical work in the same country uses SI units.
A blood pressure reading such as 120 over 80 is expressed in millimetres of mercury, referring to the height of a mercury column the pressure would support. Converting 120 mmHg gives roughly 16.0 kPa, and 80 mmHg gives about 10.7 kPa. Medicine retains mmHg because the original sphygmomanometers were literal mercury columns and decades of diagnostic thresholds are defined in those numbers, so switching units would risk clinical confusion for no benefit.
Absolute pressure cannot fall below zero, since zero represents a perfect vacuum with no molecular collisions at all. Gauge pressure, however, is routinely negative because it is measured relative to atmosphere, so a partial vacuum in a suction line or an intake manifold reads below zero on a gauge. A reading of −10 kPa gauge simply means the absolute pressure is about 91.3 kPa at sea level, which is still comfortably positive.