Calcady™
Home / Unit / Pressure Conversion Calculator

Pressure Conversion Calculator

Convert pressure between PSI, bar, atm, Pa, kPa, mmHg, inHg, and other pressure units instantly.

Pressure Scale

2.41317

Converted Pressure

2.41317
Bar
Email LinkText/SMSWhatsApp

What is Pressure Units: Pascal, PSI, Bar & Atmospheres?

How all pressure units reduce to force-per-unit-area, why the SI Pascal is tiny compared to everyday units, and the key reference points every engineer should know.

Mathematical Foundation

Definition of Pressure
P=FAP = \frac{F}{A}
FF= Force applied perpendicular to a surface (in Newtons)
AA= Area over which the force is distributed (in m²)
PP= Pressure in Pascals (Pa). 1 Pa = 1 N/m²

Laws & Principles

  • Why PSI Dominates US Industry: PSI (pounds per square inch) is deeply embedded in US manufacturing, tire standards, pressure vessel codes, and HVAC because the foot-pound-second system was the de facto engineering standard before metrication. Standard car tire pressure (32–35 PSI) = 2.2–2.4 bar = 220–240 kPa.
  • The Bar Advantage: 1 bar ≈ 1 atmosphere (1 atm = 1.01325 bar exactly), making bar the preferred unit in meteorology and chemistry. Gauge pressure (PSIG/bar-g) measures pressure relative to local atmospheric pressure, while absolute pressure (PSIA/bar-a) includes atmospheric pressure. Confusing gauge vs. absolute is a common and dangerous engineering error.

Step-by-Step Example Walkthrough

" Converting standard tire inflation pressure of 35 PSI to bar and kPa. "

  1. 1 PSI = 6,894.76 Pascals (Pa) exactly.
  2. 35 PSI × 6,894.76 = 241,316 Pa = 241.3 kPa.
  3. 1 bar = 100,000 Pa.
  4. 241,316 Pa ÷ 100,000 = 2.413 bar.
Final Result: 35 PSI = 241.3 kPa = 2.413 bar (all gauge pressure measurements)

Quick Answer: Common Pressure Conversions

1 atm = 14.696 PSI = 1.01325 bar = 101,325 Pa. 1 bar = 14.504 PSI. 1 PSI = 6,894.76 Pa. Tire pressure is typically in PSI (US) or bar (Europe). Blood pressure is in mmHg. Weather uses inHg (US) or hPa/mbar (global).

Pressure Unit Reference

Unit= PSICommon Use
1 atmosphere (atm)14.696Sea-level reference
1 bar14.504European tire pressure, industrial
100 kPa14.504Engineering, science
760 mmHg14.696Blood pressure, lab vacuum
29.92 inHg14.696US weather, aviation altimeters

Frequently Asked Questions

What is the difference between PSI and PSIG?

PSI (or PSIA) is absolute pressure — measured from a perfect vacuum. PSIG is gauge pressure — measured from atmospheric pressure. At sea level: PSIA = PSIG + 14.696. A tire gauge reading 35 PSIG is actually 49.7 PSIA. Most everyday pressure references (tires, shop air, water lines) use gauge pressure (PSIG).

Why is blood pressure measured in mmHg?

Early blood pressure instruments (sphygmomanometers) used a column of mercury (Hg) displaced by arm cuff pressure. A reading of "120/80" means the systolic pressure pushes mercury up 120 millimeters. Though modern devices are digital, the mmHg unit persists because the entire medical literature and drug dosing protocols are calibrated to it.

How do I convert tire pressure between PSI and bar?

Divide PSI by 14.504 to get bar (or roughly divide by 14.5). Common conversions: 30 PSI ≈ 2.07 bar, 32 PSI ≈ 2.21 bar, 35 PSI ≈ 2.41 bar, 40 PSI ≈ 2.76 bar. European cars list tire pressure in bar on the door jamb sticker. If renting a car abroad and the gas station pump shows bar, use this converter to find the right setting.

Related Converters