Pascals to Bar Converter
Common Conversions
| Pa | bar |
|---|---|
| 100 | 0.001 |
| 1000 | 0.01 |
| 10000 | 0.1 |
| 50000 | 0.5 |
| 100000 | 1 |
| 101325 | 1.01325 |
| 200000 | 2 |
| 500000 | 5 |
| 1000000 | 10 |
| 5000000 | 50 |
| 10000000 | 100 |
Why this conversion matters in chemistry
The pascal is the SI base for pressure; the bar is what IUPAC chose as the reference pressure for standard-state thermodynamic tables back in 1982. The factor between them is exactly 10⁵ — 1 bar is 100,000 Pa by construction. Vacuum-system datasheets quote ultimate pressures in pascals (turbo pumps reach 10⁻⁷ Pa or below), but the lab summary often translates back into bar. A turbopump base pressure of 5 × 10⁻⁷ Pa is 5 × 10⁻¹² bar — the kind of figure that confirms residual-gas contamination is below the threshold for ion-source stability in a mass-spec setup.
Formula
Where the factor comes from
The bar is not a prefixed pascal, and that distinction is the whole of the derivation. Kilo, milli and the rest are names for powers of ten inside the SI; the bar is a separate named unit, outside the SI but tolerated alongside it, whose defining equation is simply 1 bar ≡ 10⁵ Pa. Somebody chose that number, picking it to sit near ordinary atmospheric pressure while staying a round power of ten of the coherent SI unit. Nothing was measured to establish it and nothing can revise it. Because the defining relation is itself a power of ten, both directions terminate — ×10⁻⁵ going one way, ×10⁵ coming back — which is exactly what the atmosphere, sitting at 101325 Pa, cannot offer.
Precision and significant figures
No rounding decision exists in either direction. The digits themselves never change; only the exponent moves, so a reading carrying three significant figures leaves with three and one carrying six leaves with six. What the tidiness invites is inflation: 101325 Pa becomes 1.01325 bar, and six figures look authoritative even when the transmitter behind them was specified at a few tenths of a percent of span. Dial gauges are blunter still. A 300 bar cylinder face specified at a percent or two of full scale is uncertain by several bar anywhere on its arc, including down near the empty end where the needle is showing 20.
Worked Examples
The defining identity — exactly 10⁵ Pa per bar by construction.
One standard atmosphere expressed in bar — slightly above the IUPAC reference, by exactly 1.3%.
Half a bar — a moderate reduced pressure for vacuum-distillation work on a high-boiling solvent.
About the elevated pressure inside a small autoclave during a sterilization or hydrothermal-synthesis run.
Common mistakes
barg and bar absolute
Most European regulator and cylinder dials read gauge bar, zeroed to the room, so a face showing 5 corresponds to about 6 bar absolute. The offset is roughly one bar: a fifth of that reading, and a rounding error at 200 bar. It bites hardest in low-pressure work, where forgetting it can double or triple the pressure that belongs in a gas-law expression.
Kilobars and gigapascals in high-pressure work
Mineral phase diagrams and diamond-anvil results are quoted in kbar or GPa, where 1 GPa is 10 kbar is 10⁹ Pa. A prefix means a hundred thousand times more pressure riding on the bar than on the pascal: a kilobar is 10⁸ Pa against the kilopascal's 10³. Confirm which unit carries the prefix before converting anything out of that literature.
R also has a cm³·bar form
Cubic equations of state are often worked with R = 83.14 cm³·bar/(mol·K), which follows from 8.314 J/(mol·K) once volume is in cubic centimeters and pressure in bar. Hand that R a pressure still expressed in pascals and every molar volume comes back a hundred thousand times off — large enough to catch, but only if you look at the number instead of moving to the next step.