# How do I convert bar to psi?

Converts bars (bar) to pounds per square inch (psi) and back, with the exact unit definitions.

- Page: https://www.acalculator.org/convert/bar-to-psi
- JSON spec: https://www.acalculator.org/convert/bar-to-psi.json
- Version: 84d3671a16d7

## Default answer

Example with the default inputs (Bars (bar) 1): 1 bar = 14.503774 psi.

## Inputs

| Key | Label | Description |
| --- | --- | --- |
| value | Bars (bar) | The amount in bars to convert. |
| result | Pounds per square inch (psi) | The same amount in pounds per square inch. |

## Outputs

| Key | Label | Description |
| --- | --- | --- |
| value | Bars (bar) | The amount in bars to convert. |
| result | Pounds per square inch (psi) | The amount in pounds per square inch. |

## Method

psi = bar × 14.503773773

## Assumptions

- 1 bar = 14.503773773 pounds per square inch, from the exact definitions in NIST SP 811.
- Exact on the typed decimals: at most 6 decimal places (6 significant digits below 0.0001), rounded half up; an answer of 1 billion or more shows at most 15 significant digits.

## Worked examples

1. value = 1 gives result = 14.503774. Source: Exact unit definitions in NIST SP 811 (2008), Appendix B.8.
2. value = 2.2 gives result = 31.908302. Source: Exact unit definitions in NIST SP 811 (2008), Appendix B.8.
3. result = 31.908302 gives value = 2.2. Source: Exact unit definitions in NIST SP 811 (2008), Appendix B.8.

## FAQ

### How many pounds per square inch are in a bar?

1 bar is 14.503774 pounds per square inch, from the exact unit definitions (NIST SP 811).

### How do I convert bar to psi?

Multiply by 14.503774: psi = bar × 14.503773773. For example, 1 bar × 14.503774 = 14.503774 psi.

### How do I convert psi back to bar?

Multiply by 0.068948, or type the pounds per square inch into the second box and the converter works it out. 1 pound per square inch is 0.068948 bars.

### Where does 14.5 psi per bar come from?

A bar is exactly 100,000 Pa, and a psi is one pound-force per square inch: 4.4482216152605 N ÷ 0.00064516 m² = 6,894.757293168 Pa (NIST SP 811). So 1 bar = 100,000 ÷ 6,894.757293168 = 14.503774 psi.

### What is 2.2 bar in psi?

31.908302 psi: 2.2 × 14.50377377.

### Does it matter if the pressure is gauge or absolute?

Not for the factor. A gauge reading in bar gives a gauge reading in psi (psig), and an absolute one gives psia. Do not mix them: absolute pressure is gauge pressure plus the air pressure around it.

### How many bar is a standard atmosphere?

1.01325 bar: a standard atmosphere is exactly 101,325 Pa (NIST SP 811), which is 14.695949 psi.

## Sources

- NIST SP 811 (2008), Guide for the Use of the International System of Units, Appendix B.8: Factors for Units Listed Alphabetically (bold factors are exact), retrieved 2026-10-18. https://www.nist.gov/pml/special-publication-811/nist-guide-si-appendix-b-conversion-factors/nist-guide-si-appendix-b8
- NIST SP 811 (2008), footnotes to Appendix B: 1 lb = 0.45359237 kg exactly (footnote 22); 1 lbf = 4.4482216152605 N exactly with standard gravity, 9.80665 m/s² (footnote 23), retrieved 2026-10-18. https://www.nist.gov/pml/special-publication-811/nist-guide-si-footnotes