Pascal to PSI Converter
Common Conversions
| Pa | psi |
|---|---|
| 100 | 0.0145 |
| 500 | 0.07252 |
| 1000 | 0.14504 |
| 5000 | 0.72519 |
| 10000 | 1.45038 |
| 50000 | 7.25189 |
| 100000 | 14.504 |
| 101325 | 14.696 |
| 200000 | 29.008 |
| 500000 | 72.519 |
| 1000000 | 145.038 |
| 10000000 | 1450.38 |
Why this conversion matters in chemistry
Microfluidic-channel pressure-drop math brings this up often. A 50 kPa channel drop across a PDMS lab on a chip is 7.25 psi, which is the inlet-pressure regulator targets when validating a flow-rate model from Hagen-Poiseuille analysis. The constant of 1.45038 × 10⁻⁴ psi per Pa comes from 1 psi = 6894.76 Pa, fixed through the international avoirdupois pound (4.4482 N) divided by the square inch (645.16 mm²). The job is closing the gap between SI-based research data and US-customary pneumatic equipment.
Formula
Where the factor comes from
A pascal is a newton per square meter and a psi is a pound-force per square inch, so the factor is two ratios stacked — one for force, one for area. The avoirdupois pound is exactly 0.45359237 kg and standard gravity is exactly 9.80665 m/s², which makes a pound-force exactly 4.4482216152605 N. An inch is exactly 0.0254 m, so a square meter holds exactly 25 000 000/16 129 square inches — 1550.0031 to eight figures, a ratio that never terminates. Take one newton, divide it by 4.4482216152605 to get pounds-force, spread it over those 1550.0031 in², and you have 1.4503773773… × 10⁻⁴ psi per pascal. Nothing along that chain was measured; the pound, the inch and standard gravity are all fixed by agreement. Most tables print the reciprocal, 6894.757293… Pa per psi, simply because it needs no exponent.
Precision and significant figures
The full factor is 1.4503773773 × 10⁻⁴. The 1.45038 × 10⁻⁴ used here is high by under two parts per million, and even a blunt 1.45 × 10⁻⁴ is low by only 2.6 parts in ten thousand — both far below what any pressure instrument resolves. What actually limits the answer is the pascal's fineness. A transducer reporting 250000 Pa to three figures supports 36.3 psi, not the 36.259 the arithmetic hands back; carrying those digits implies a gauge that can split hundredths of a psi. Match the output's figure count to the reading, and check the prefix first — SI-native instruments usually display kPa or MPa, so the digits in front of you have often already been shifted.
Worked Examples
Standard atmospheric pressure expressed in both unit systems.
About a small gauge pressure on a low-range manometer.
About 2 bar — the pressure inside a sealed reactor at moderate buildup.
About a high-pressure reaction condition for catalytic chemistry.
Common mistakes
kPa on the display, Pa in the formula
SI-native transducers and reactor controllers almost always read in kilopascals or megapascals; bare pascals turn up mainly in vacuum work and textbook problems. Feed a 250 kPa display straight into a pascal-based factor and you get 0.036 psi instead of 36.3. The result is small enough to pass as a vacuum reading rather than an obvious blunder, which is exactly what lets it survive.
psi is pound-force, not pound-mass
Building the factor from the pound alone gives 0.45359237 ÷ (6.4516 × 10⁻⁴) = 703.07, which is kilograms-force per square meter, not pascals; multiplying by 9.80665 recovers 6894.757. That 703 still appears in older hydraulic tables. Divide pascals by it instead of by 6894.757 and every psi figure comes out 9.81 times too large.
Pascals are absolute, psi dials usually are not
A transducer's pascal reading is an absolute pressure. A psi dial on a regulator or reactor almost always shows gauge, where zero on the face means ambient. Convert 50000 Pa and you get 7.25 psi absolute — a partial vacuum — while a dial reading 7.25 means about 21.9 psi absolute. US vacuum equipment adds a third convention, reporting inches of mercury below ambient.