Conversion tool

Pressure Converter

Convert between PSI, bar, kPa, Pa, atmospheres and mmHg. All factors are exact values referenced to NIST Special Publication 811 — not rounded approximations.

From

Formula & conversion factors

1 bar = 100,000 Pa  (exact, SI-accepted)
1 atm = 101,325 Pa  (exact, by international agreement)
1 PSI = 6,894.757293168 Pa  (exact, NIST SP811)
1 mmHg = 133.322387415 Pa  (exact, conventional mmHg, NIST SP811)

General form: value_Pa = value_unit × factor_to_Pa
         result = value_Pa ÷ factor_of_target_unit

1Worked example: a pressure transmitter reads 14.7 PSI. 14.7 × 6894.757293168 = 101,353 Pa → ÷ 100,000 = 1.0135 bar (this is standard atmospheric pressure at sea level, as expected for a sanity check).

Reference standard: Base unit: pascal (Pa), the SI derived unit of pressure (1 Pa = 1 N/m²). Conversion factors per NIST Special Publication 811 (Guide for the Use of the International System of Units) and the BIPM SI Brochure, 9th edition.

Common questions

How do you convert PSI to bar?

Multiply PSI by 6894.757293168 to get pascals, then divide by 100,000. As a quick estimate, 1 PSI ≈ 0.0689 bar.

Why is 1 atm exactly 101,325 Pa and not a rounder number?

Standard atmosphere was fixed at exactly 101,325 Pa by international agreement (based on historical mercury barometer measurements at 0°C, standard gravity), not derived from a metric round number.

What pressure unit do 4–20mA transmitters typically use?

Industrial pressure transmitters are commonly specified in PSI (US) or bar/kPa (rest of world). This converter is the same math used in our upcoming 4–20mA scaling calculator.