# PSIG to PSIA Converter

URL: https://speedycalculator.com/calculators/conversion/psig-to-psia-conversion/
Last updated: 2026-10-25

> The PSIG to PSIA converter adds atmospheric pressure to a gauge reading to give absolute pressure, and subtracts it to go back. You can change the atmospheric pressure for altitude or weather.

## Inputs

- Gauge pressure (psig)
- Atmospheric pressure (psi, kPa, hPa, bar, inHg)

## Results

- Absolute pressure

## Formula

```
psia = psig + atmospheric pressure (14.696 psi at sea level)
```

## Explanation

Gauges read zero at ambient air pressure (gauge pressure, psig), but gas laws and many specifications need absolute pressure (psia), measured from a perfect vacuum.

### How to use the PSIG to PSIA Converter

- **Gauge pressure**
- **Atmospheric pressure**
- Every result field is editable: type into **Absolute pressure** and **Gauge pressure** plus every other field update to match.

Results update as you type, and every field accepts the units shown in its menu.

### How it works

The atmospheric pressure is added to the gauge reading. Type an absolute pressure into the result to get the gauge reading.

### Inputs explained

FieldWhat to enterGauge pressureIn psigAtmospheric pressureUnits: psi, kPa, hPa, bar, inHg

### Example values

How the main result changes when **Gauge pressure** changes and everything else stays at the example values above:

Gauge pressure (psig)Absolute pressure (psi)1529.695922.537.19593044.695937.552.19594559.69596074.6959

## Worked example

Inputs — Gauge pressure: 30 psig; Atmospheric pressure: 14.6959 psi.

Results — **Absolute pressure = 44.6959 psi**.

## FAQ

**What is 0 psig in psia?**
14.696 psia at sea level.

**Can absolute pressure be negative?**
No; 0 psia is a perfect vacuum.

**What formula does the PSIG to PSIA Converter use?**
psia = psig + atmospheric pressure (14.696 psi at sea level).


## Sources

- [NIST Special Publication 811 – Guide for the Use of the International System of Units](https://www.nist.gov/pml/special-publication-811)
- [NIST Handbook 44 Appendix C – General tables of units of measurement](https://www.nist.gov/pml/owm/nist-handbook-44-current-edition)