Convert PSI to Bar – Pressure Converter
This converter converts a single numeric pressure value from pounds per square inch (psi) to bar. It is intended for engineering, maintenance, and general-purpose use where a direct, fixed mathematical relationship applies.
Use the result as a unit-conversion reference. For critical measurements (safety systems, legal metrology, high-precision instrumentation) follow instrument calibration procedures and applicable standards before acting on converted values.
Interactive Converter
Convert between psi (pounds per square inch) and bar with precision rounding.
Quick reference table
| PSI (Pounds per Square Inch) | Bar |
|---|---|
| 1 psi | 0.0689 bar |
| 5 psi | 0.3447 bar |
| 10 psi | 0.6895 bar |
| 25 psi | 1.7237 bar |
| 50 psi | 3.4474 bar |
| 100 psi | 6.8948 bar |
Methodology
The conversion uses the exact defined relationship between the two units as established by international metrology references. One bar is defined relative to pascals and the pascal is the SI derived unit for pressure. The tool applies that fixed mathematical factor to transform psi to bar.
When converting gauge readings (psig) versus absolute readings (psia), the converter changes only units; it does not add or subtract atmospheric pressure. For applications requiring absolute pressure, first ensure the input is in absolute units or convert gauge to absolute by adding the local atmospheric pressure.
Recommended practice: for regulatory or safety-critical work, consult calibration records and standards (for example NIST guidance on units and calibration, ISO standards on quantities and units, and applicable industry safety standards). Round results consistent with measurement uncertainty and the precision of your instrument.
Worked examples
14.5037737735 psi → 1.0000000000 bar (reference equivalence)
30 psi × 0.0689475729 = 2.068427187 bar (typical tire-pressure conversion; round to 2.07 bar for display)
0.5 psi × 0.0689475729 = 0.03447378645 bar (useful for low-pressure differentials)
Key takeaways
This converter applies the fixed, internationally recognized relationship between psi and bar. Use it for quick unit conversions but rely on calibrated instruments and standards guidance for safety-critical, regulatory, or high-precision work.
When converting between gauge and absolute pressures, account for atmospheric pressure outside the unit conversion step. Follow NIST, ISO, and relevant regulatory guidance for traceability and compliance.
Further resources
Expert Q&A
Does this converter handle gauge (psig) and absolute (psia) pressure differences?
This tool converts numeric values between units only. It does not add or remove atmospheric pressure. If you have a gauge reading (psig) and need absolute pressure (psia), add local atmospheric pressure (approximately 14.7 psi at sea level) before converting. For accurate absolute conversions use measured local barometric pressure and account for elevation.
How many decimal places should I use?
Choose rounding consistent with the measurement uncertainty of your pressure instrument. For general-purpose conversions 2 decimal places is common; for laboratory or calibration work use 3 or more decimals. Always document rounding when results inform safety or compliance decisions.
Where does the conversion factor come from and how accurate is it?
The conversion factor is derived from the exact SI definitions and internationally recognized relationships between pascals, bars, and pounds per square inch. For traceable measurements, follow calibration and uncertainty statements from standards bodies such as NIST and ISO.
Are there regulatory limits expressed in bar or psi I should be aware of?
Regulatory limits depend on jurisdiction and application (pressure vessels, pipelines, workplace safety). Refer to applicable regulations and standards (for example OSHA rules for pressure-related hazards and industry-specific codes). Use certified calculations and calibrated instruments for compliance checks.
Can I use this for very high or very low pressures?
Mathematically yes—the conversion relationship is linear. Practically, for extreme pressures consider instrument range, nonideal behavior, and whether specialized units or correction factors apply. For critical or high-precision measurements consult appropriate standards and instrumentation specifications.
Sources & citations
- NIST Reference: Units and Constants — Pressure — https://physics.nist.gov/cuu/Units/pressure.html
- BIPM / SI Derived Units (overview of derived units including pressure) — https://www.bipm.org/en/measurement-units/si-base-and-derived-units
- ISO standard series on quantities and units (reference for unit definitions) — https://www.iso.org/standard/30669.html
- OSHA — Occupational Safety and Health Administration (safety and workplace regulations) — https://www.osha.gov/
- IEEE Standards & Publications (instrumentation and measurement practices) — https://standards.ieee.org/