Bar to Pascals Converter
Common Conversions
| bar | Pa |
|---|---|
| 0.001 | 100 |
| 0.01 | 1000 |
| 0.1 | 10000 |
| 0.5 | 50000 |
| 1 | 100000 |
| 1.01325 | 101325 |
| 2 | 200000 |
| 5 | 500000 |
| 10 | 1000000 |
| 100 | 10000000 |
| 200 | 20000000 |
Why this conversion matters in chemistry
Bar is what most modern chemistry data uses for pressure — it's IUPAC's reference for tabulated thermodynamic standard states, and the numbers come out tidy. The pascal is the SI base unit, but at atmospheric scale it gets unwieldy: 1 bar is 100,000 Pa, and a high-pressure synthesis at 200 bar lives at 20 MPa or 2 × 10⁷ Pa. The conversion is exact through the bar's definition, so the only thing it changes is the size of the exponent. The arithmetic earns its keep mostly when an equation written in pure SI — Navier-Stokes, Bernoulli, anything with R in J/(mol·K) — needs the pressure in pascals to make the rest of the units cancel.
Formula
Where the factor comes from
There is no factor to derive here, only a definition to restate. Unlike the atmosphere, which was reverse-engineered from a mercury column, or the psi, which is assembled out of a pound and an inch, the bar was never tied to a physical referent anyone had to measure. It was declared equal to 10⁵ pascals and has been exactly that ever since, so the multiplier is a power of ten with no chain of constants standing behind it. In SI base units a pascal is kg·m⁻¹·s⁻², making a bar 10⁵ kg·m⁻¹·s⁻² and the arithmetic a five-place shift of the decimal point. The same definition puts a bar at exactly 0.1 MPa, which is how high-pressure and geochemical work generally prefers to write it.
Precision and significant figures
No uncertainty is introduced and no significant figures are gained: 2.5 bar becomes 2.5 × 10⁵ Pa with two figures intact, whereas writing 250000 Pa invites a reader to count six. That is the real difficulty with this direction — the format rather than the number. Five orders of magnitude of trailing zeros make transcription slips easy and disguise the precision of the original reading, so scientific notation or a megapascal is usually the better place to land. At the other end the pascal earns its keep: a vacuum at 10⁻⁶ bar reads as 10⁻¹ Pa, a number you can hold in your head, and it stays legible for several more decades of pressure below that.
Worked Examples
The defining identity — 1 bar is exactly 10⁵ Pa by construction.
One standard atmosphere expressed in pascals — the value any sea-level gas-law calculation in pure SI starts from.
A low vacuum, the kind a rotary-vane pump pulls when bringing a Schlenk line to working pressure.
The pressure inside a full compressed-gas cylinder, also written as 20 MPa in process documentation.
Common mistakes
N/mm² on a datasheet means megapascals
Vessel and fitting datasheets often quote pressure as N/mm². A newton per square millimeter is 10⁶ Pa, which is 1 MPa or 10 bar — not the newton per square meter that the pascal is. Reading N/mm² as though it were pascals understates a rating by a factor of a million and makes any comparison against a converted bar value meaningless.
Liquid head adds to the gauge reading
A transducer mounted at the base of a tall vessel senses the applied pressure plus the hydrostatic head above it. Two meters of water contributes about 19600 Pa, near 0.2 bar. Converting that dial to pascals and calling the result the vapor-space pressure overstates it by the head, which matters most when the vapor-space pressure is itself small.
Kilobar in the high-pressure literature
High-pressure and mineral work reports in kilobars and gigapascals. One kbar is 10⁸ Pa, which is 100 MPa. Read a kbar figure as bar during a conversion and the pressure comes out a thousandfold low, landing in a regime where none of the described behavior occurs. Check the prefix on the bar before touching the exponent on the pascal.