The conversion
Both are gauge pressures — measured relative to whatever the atmosphere is doing outside the pipe. Dividing by 14.5038 changes the unit and leaves the reference basis exactly where it was. That sounds obvious written down, and it is still the most common pressure mistake in plant work.
Reference table
| psig | barg | kPa (g) | kg/cm² (g) | psia |
|---|---|---|---|---|
| 1 | 0.0689 | 6.9 | 0.0703 | 15.70 |
| 5 | 0.3447 | 34.5 | 0.3515 | 19.70 |
| 10 | 0.6895 | 68.9 | 0.7031 | 24.70 |
| 15 | 1.0342 | 103.4 | 1.0546 | 29.70 |
| 20 | 1.3789 | 137.9 | 1.4062 | 34.70 |
| 30 | 2.0684 | 206.8 | 2.1093 | 44.70 |
| 50 | 3.4474 | 344.7 | 3.5154 | 64.70 |
| 75 | 5.1711 | 517.1 | 5.2731 | 89.70 |
| 100 | 6.8947 | 689.5 | 7.0309 | 114.70 |
| 125 | 8.6184 | 861.8 | 8.7886 | 139.70 |
| 150 | 10.3421 | 1034.2 | 10.5463 | 164.70 |
| 200 | 13.7895 | 1379.0 | 14.0617 | 214.70 |
| 250 | 17.2369 | 1723.7 | 17.5772 | 264.70 |
| 300 | 20.6842 | 2068.4 | 21.0926 | 314.70 |
| 400 | 27.5790 | 2757.9 | 28.1235 | 414.70 |
| 500 | 34.4737 | 3447.4 | 35.1543 | 514.70 |
Where the gauge-to-absolute step actually matters
Most day-to-day work stays in gauge and never needs the conversion. Four situations need absolute, and getting them wrong introduces roughly one atmosphere of error:
- Steam tables. Published in absolute. A 10 barg header is 11.01 bara, which is 184.1 °C — not the 179.9 °C that 10 bara gives. See the saturated steam table.
- Gas law work. Density, actual-to-standard flow conversion and compressor calculations all need absolute pressure, and the proportional error is largest at low pressures.
- Compressible valve sizing. The pressure drop ratio x = ΔP/P₁ uses absolute inlet pressure — see the gas and steam Cv calculator.
- Vacuum service. Gauge goes negative, absolute never does. −10 psig is 4.7 psia.
Field notes
- kg/cm² is not bar. It is 0.980665 bar — a 2% difference that looks exactly like instrument drift rather than a unit error. It appears on a lot of older Indian and Japanese plant documentation, paired with newer equipment ranged in bar.
- Altitude changes the absolute conversion. Atmospheric pressure falls roughly 1.2% per 100 m near sea level, so at 1,500 m it is about 84.6 kPa rather than 101.3. The gauge to absolute converter handles that properly.
- Write the suffix every time. "10 bar" is ambiguous; "10 barg" is not. It costs one character and removes an entire class of error — more in the pressure units guide.
- Low-range work uses different units entirely — draft, filter DP and room pressurisation live in mmWC. The mmWC converter covers those.
Frequently asked questions
How do I convert psig to barg?
Divide by 14.5038. So 100 psig is 6.895 barg, and 1 barg is 14.504 psig. The gauge reference carries straight across — converting the unit never converts the reference basis.
What is 100 psig in barg?
100 psig equals 6.89474 barg, which is 689.5 kPa gauge or 7.031 kg/cm² gauge. In absolute terms it is 7.908 bara or 114.7 psia at sea level.
Is psig the same as psia?
No. psig is measured relative to local atmospheric pressure; psia is measured relative to a perfect vacuum. psia = psig + 14.696 at sea level, so 100 psig is 114.7 psia.
How do I convert psig to kg/cm²?
Divide by 14.223. One kg/cm² equals 14.223 psi, so 100 psig is 7.031 kg/cm² gauge. Note that kg/cm² is not the same as bar — it is 0.980665 bar, a 2% difference that matters at calibration tolerances.
Provided for reference and education. For every pressure unit at once, use the full pressure unit converter. See our disclaimer.