Convert Millibars to psi

Formula

psi = mbar × 0.01450377377302

or psi = mbar ÷ 68.94757293168

Derivation from SI units:

• 1 mbar = 10⁻³ bar = 100 Pa = 1 hPa
• 1 psi = 1 lbf/in² = (0.45359237 kg × 9.80665 m/s²) ÷ (0.0254 m)² = 6894.757293168 Pa
• 1 mbar = 100 Pa ÷ 6894.757293168 Pa per psi = 0.01450377377302 psi

Both units are defined exactly, so the factor is exact. Millibar definition: millibar; psi definition: psi.

Worked examples

1. A reading of 20 mbar converts to 0.2900754755 psi.
   20 mbar × 0.01450377377 = 0.2900754755 psi
2. A value of 900 mbar is 13.0533964 psi.
   900 mbar × 0.01450377377 = 13.0533964 psi

Where it's used

Millibars are used for weather maps and barometers (sea level ≈ 1013 mbar), while psi appear in tyre pressure in the United States (about 30–35 psi for cars). Both measure pressure, stress and differential pressure (force per unit area), so the conversion is a fixed factor.

Millibar to other pressure units

Frequently asked questions

Sources

• Guide for the Use of the International System of Units (SI), NIST Special Publication 811, 2008 Edition, National Institute of Standards and Technology , Appendix B.8, "millibar".
• Guide for the Use of the International System of Units (SI), NIST Special Publication 811, 2008 Edition, National Institute of Standards and Technology , Appendix B.8, "pound-force per square inch (psi)".

Last reviewed: 2026-10-15. Factors are stored exactly and computed with 50-digit decimal arithmetic. See how we verify conversion factors.