PSIG to PSIA Converter
Convert psig to psia and back. Enter gauge pressure (or switch to absolute) and set your local atmospheric pressure; sea level defaults to 14.696 psi.
Example: with Pressure (psi) 30 · Direction psig → psia · Local atmospheric pressure (psi) 14.696 → Result: 44.696 psia.
- Calculation30 psig + 14.696 = 44.696 psia
- Reference usedAtmosphere used: 14.696 psi (sea level)
Computed by the calculator below using its default values. Change any input to see your own numbers.
psia = psig + atmospheric pressure. At sea level that atmosphere is 14.696 psi, so a gauge reading of 0 psig is already 14.696 psia.
Gauge zero is really one atmosphere
A pressure gauge reads zero when it is open to the air, because it measures how much a system exceeds the surrounding atmosphere. Absolute pressure instead counts up from a perfect vacuum, so it always includes the roughly 14.7 psi the atmosphere already applies. Converting gauge to absolute is therefore just addition.
That offset matters whenever the physics cares about total pressure. Gas-law calculations, boiling points, compressor ratios, and vacuum work all use absolute pressure. At sea level you add 14.696 psi; on a mountain you add less, because there is simply less air pressing down from overhead.
How it’s calculated
psia = psig + P_atm; psig = psia − P_atm. The default P_atm is 14.696 psi, the standard sea-level atmosphere (International Standard Atmosphere). At altitude, replace it with your local barometric pressure, which falls roughly a few tenths of a psi per thousand feet of elevation.
Assumes the atmospheric value you enter is correct for your elevation and weather; real barometric pressure varies a few percent day to day.
psig to psia at sea level
| psig | + atmosphere | psia |
|---|---|---|
| 0 psig | 14.696 | 14.696 psia |
| 10 psig | 14.696 | 24.696 psia |
| 30 psig | 14.696 | 44.696 psia |
| 100 psig | 14.696 | 114.696 psia |
| -14.696 psig | 14.696 | 0 psia (full vacuum) |
Computed as psia = psig + local atmosphere; 14.696 psi is standard sea-level pressure (ISA).
Common mistakes
- Using 14.7 at high altitude — Denver sits near 12.2 psi, so absolute readings there are lower than the sea-level formula suggests.
- Adding 14.696 to a value that is already absolute, which double counts the atmosphere.
- Forgetting that 0 psig is not zero pressure; it is atmospheric, or 14.696 psia.
Frequently asked questions
How do I convert psig to psia?
Add atmospheric pressure: psia = psig + 14.696 at sea level. A tire at 32 psig is about 46.7 psia.
Why 14.696?
That is standard atmospheric pressure at sea level in pounds per square inch. It is the weight of the column of air pressing on everything around you.
Does altitude change the answer?
Yes. Atmospheric pressure drops with elevation, so at altitude you should replace 14.696 with your local barometric value, which this tool lets you set.
What is 0 psig in psia?
14.696 psia. Gauge pressure is measured relative to the surrounding air, so a gauge reading of zero still carries one atmosphere of absolute pressure.