Bar to PSIG Converter

Process gauges often read psig (psi above atmosphere) while datasheets and simulations list bar absolute. This calculator bridges them, adding or removing the atmospheric offset automatically so you don’t double-count or forget ambient pressure.

How the conversion works

Atmospheric pressure at sea level is about $14.6959\,\text{psi} = 1.01325\,\text{bar}$. Conversions:

$$P_{\text{psi,abs}} = P_{\text{bar,abs}} \times 14.5038$$ $$P_{\text{psig}} = P_{\text{psi,abs}} - 14.6959$$ $$P_{\text{bar,abs}} = \frac{P_{\text{psig}} + 14.6959}{14.5038}$$

The tool uses Pascals internally, applying the same offset for psig every time.

Units and conversions

Worked examples

1. Bar absolute to psig
   Given $5.0\,\text{bar (abs)}$:

   $$P_{\text{psia}} = 5.0 \times 14.5038 \approx 72.52\,\text{psia}$$ $$P_{\text{psig}} = 72.52 - 14.6959 \approx 57.82\,\text{psig}$$

   Result: 57.8 psig.

2. Gauge reading to bar absolute
   Given $60\,\text{psig}$:

   $$P_{\text{psia}} = 60 + 14.6959 = 74.6959\,\text{psia}$$ $$P_{\text{bar,abs}} = \frac{74.6959}{14.5038} \approx 5.15\,\text{bar}$$

   Result: 5.15 bar (abs).

Tips and pitfalls

• Check instrument labels: psig is gauge, psia is absolute. Mixing them is the usual cause of one-atmosphere mistakes.
• At altitude, local atmospheric pressure changes; psig still references the local ambient. Add the measured ambient if you need absolute values.
• When sizing relief valves, work in absolute units end-to-end, then report psig only for operators.

References and further reading

• Bar (unit) — Wikipedia
• Pound per square inch — Wikipedia
• Standard atmosphere (unit) — Wikipedia