What is the difference between bar and atm?

Bar and atm (standard atmosphere) are both units of pressure. 1 atm = 1.01325 bar. They are very close in value — 1 bar is approximately 0.987 atm. The bar is commonly used in industry and engineering, while atm is used in chemistry, aviation, and as a reference for standard conditions.

How do you convert PSI to bar?

To convert PSI to bar, divide by 14.5038: bar = PSI / 14.5038. For example, 100 PSI = 100 / 14.5038 = 6.895 bar. Conversely, to convert bar to PSI, multiply by 14.5038: PSI = bar × 14.5038.

What is the difference between gauge and absolute pressure?

Absolute pressure is measured relative to a perfect vacuum (zero reference). Gauge pressure is measured relative to atmospheric pressure. The relationship is: P_absolute = P_gauge + P_atmospheric. For example, a tire gauge reading 32 PSI (gauge) means 32 + 14.7 = 46.7 PSI absolute. Units often use 'g' or 'a' suffix: psig (gauge), psia (absolute), barg, bara.

What is mmHg used for?

mmHg (millimeters of mercury), also called torr, is commonly used in medicine for blood pressure measurement (e.g., 120/80 mmHg), in vacuum technology, and in meteorology. 1 mmHg = 133.322 Pa. Standard atmospheric pressure is 760 mmHg.

What is the difference between kPa and MPa?

Both are SI units of pressure. 1 MPa = 1000 kPa. kPa (kilopascal) is used for lower pressures like tire pressure and HVAC. MPa (megapascal) is used for higher pressures like hydraulic systems, material strength, and water jetting. For reference: 1 bar ≈ 100 kPa = 0.1 MPa.

Free Engineering Tool

Pressure Unit Converter

Convert between all common pressure units instantly. Enter a value and select the input unit — all conversions are shown simultaneously.

12 Units bar ↔ PSI ↔ MPa atm ↔ kgf/cm²

Results

Conversion Method

All conversions go through Pascal (Pa) as the base SI unit. To convert from unit A to unit B:

Value_B = Value_A × (Factor_A / Factor_B)

Where each factor represents how many Pascals equal one unit.

Conversion Factors (to Pascal)

Unit	Symbol	1 unit = … Pa
Pascal	Pa	1
Kilopascal	kPa	1,000
Megapascal	MPa	1,000,000
Bar	bar	100,000
Millibar	mbar	100
PSI	PSI	6,894.76
Standard atmosphere	atm	101,325
Technical atmosphere	kgf/cm² (at)	98,066.5
Millimeters of mercury	mmHg (torr)	133.322
Inches of mercury	inHg	3,386.39
Millimeters of water	mmH₂O	9.80665
Inches of water	inH₂O	249.089

Common Conversions

Quick Reference

1 bar = 14.5038 PSI = 100 kPa = 0.1 MPa

1 atm = 1.01325 bar = 14.696 PSI = 101.325 kPa

1 MPa = 10 bar = 145.038 PSI

1 kgf/cm² = 0.98067 bar = 14.223 PSI

1 atm = 760 mmHg = 29.921 inHg

Gauge vs. Absolute Pressure

Important: This converter handles absolute values. Gauge pressure (barg, psig) is measured relative to atmospheric pressure. To convert: P_absolute = P_gauge + P_atmospheric. Standard atmospheric pressure = 1 atm = 1.01325 bar = 14.696 PSI.

⚠️ Note: mmH₂O and inH₂O values depend on water temperature (density). The factors used here are at 4 °C (maximum density). At room temperature, actual values may differ by ~0.2%.

Pressure Unit Converter | bar ↔ PSI ↔ MPa ↔ atm ↔ kgf/cm²

Published by Nikolai Shelkovenko on February 15, 2026 February 15, 2026