PSI to Kilopascals Converter
Common Conversions
| psi | kPa |
|---|---|
| 1 | 6.895 |
| 5 | 34.47 |
| 10 | 68.95 |
| 14.696 | 101.325 |
| 25 | 172.4 |
| 50 | 344.7 |
| 100 | 689.5 |
| 200 | 1379 |
| 500 | 3447 |
| 1000 | 6895 |
| 2000 | 13790 |
| 3000 | 20684 |
Why this conversion matters in chemistry
Compressed-gas regulators, lab air-line pressure gauges, and US-built instrumentation all read in psi. Most chemistry calculations want kPa, not least because R = 8.314 J/(mol·K) cooperates with SI base units. The factor is 6.89476 kPa per psi, exact through the SI definitions: 1 lbf = 4.44822 N and 1 in² = 6.4516 × 10⁻⁴ m². A 100 psi reactor pressure is 689 kPa; a 2200 psi cylinder pressure is 15.2 MPa. The conversion comes up most when a US-spec gauge reading has to feed a calculation written with R in J/(mol·K) — without it, the answer drops by nearly a factor of 7.
Formula
Where the factor comes from
Unusually for a unit still in daily technical use, the psi carries an acceleration inside its definition. A pound-force is the avoirdupois pound, exactly 0.45359237 kg, multiplied by standard gravity, exactly 9.80665 m/s² — a conventional value, not the local one. That product, 4.4482216152605 N, spread over a square inch of exactly 6.4516 × 10⁻⁴ m², gives 6894.757293… Pa, and the kilo prefix brings it to 6.894757293… kPa. Every input is a definition, so the factor has no uncertainty attached. The conventional gravity does have a physical consequence, though: instruments that generate pressure from a stack of masses, deadweight testers among them, respond to local g, which departs from 9.80665 by up to about a quarter of a percent with latitude and elevation and has to be corrected for.
Precision and significant figures
6.89476 sits within half a part per million of exact and 6.895 within thirty-five — either is more than this pair will ever need. Let the reading govern instead. On a Bourdon dial read to the nearest 5 psi, one division spans about 34 kPa, so around 100 psi writing 689.5 kPa claims four figures the gauge cannot support; 690 kPa is the honest form. At the top of the range the unit itself turns awkward. A 2200 psi cylinder is 15168 kPa, which the high-pressure literature would write as 15.2 MPa, and when a converted value is going to be read by someone else the megapascal is the safer container.
Worked Examples
One standard atmosphere expressed in both unit conventions — the calibration anchor for any gauge.
About a full compressed-nitrogen cylinder at delivery — the value behind any inert-gas line sizing calculation.
A typical compressed-air line pressure in many US-spec lab buildings.
A common operating pressure for a small-scale hydrogenation reactor.
Common mistakes
The multiply-by-seven shortcut in recorded work
Seven is 1.53 percent high, and always high — it never averages out over a series. 500 psi rounds to 3500 kPa against a true 3447, and pushed through PV = nRT that overstates the mole count by the same 1.53 percent in every run. Keep the shortcut for checking whether a regulator setting is roughly right, and use the real factor for anything written down.
Gauge-to-absolute wants local ambient
Adding a standard atmosphere to a converted gauge pressure quietly assumes you are near sea level. A lab at 1600 m sits closer to 83 kPa, so a 50 psi line at 345 kPa gauge is about 428 kPa absolute there rather than 446. Published barometric values arrive in hectopascals, millibar or inches of mercury as often as kilopascals, which puts another conversion ahead of the addition.
Backpressure carries its running conditions
Chromatographic backpressure converted from psi to kilopascals is comparable to another system's figure only at the same flow rate, mobile-phase composition and column temperature, since viscosity moves with all three. The converted number is exact. Treating it as a property of the column rather than of the whole running condition is where the comparison quietly stops meaning anything.