Pressure values appear in completely different contexts: tyre pressure is shown in bar or PSI at the pump, blood pressure in mmHg at the doctor's, atmospheric pressure in mbar in weather forecasts, and hydraulic pressure in industrial machinery in bar or MPa. The pressure converter switches between all common pressure units — including the SI unit pascal, which is indispensable in technical calculations.
Step by Step: How to Use the Pressure Converter
- Enter the source value: Type in the known pressure — e.g. 2.5 (tyre pressure in bar) or 120 (blood pressure in mmHg).
- Select the source unit: bar (engineering and everyday use), mbar (meteorology), pascal / kPa / MPa (SI units), PSI (imperial, US tyres), atm (atmospheres), mmHg / Torr (medical), kgf/cm² (older technical documents).
- Select the target unit: All units are displayed simultaneously. Especially useful when importing American machinery (PSI → bar) or working with medical devices (mmHg → kPa).
- Note gauge vs. absolute pressure: Tyre pressure is gauge pressure (above atmospheric pressure); gas lines are also measured in gauge pressure. Absolute pressure = gauge pressure + atmospheric pressure (1.01325 bar).
- Calculate diving pressure: For every 10 m of water depth, absolute pressure increases by 1 bar. At 30 m depth: 1 bar (atmosphere) + 3 bar (water column) = 4 bar absolute.
Practical Examples
Example 1 – Tyre pressure in the USA: US tyre pressure recommendation 36 PSI (typical for an SUV). In bar: 36 ÷ 14.504 = 2.48 bar. European pumps show bar — so inflate to 2.5 bar.
Example 2 – Blood pressure reading: Normal blood pressure 120/80 mmHg. In kPa: 120 × 0.1333 = 16.0 kPa systolic; 80 × 0.1333 = 10.7 kPa diastolic. Relevant for medical device documentation.
Example 3 – Hydraulic power unit: Hydraulic pump operating pressure 200 bar. In MPa: 200 ÷ 10 = 20 MPa. In PSI: 200 × 14.504 = 2,901 PSI — as stated in American hydraulic valve data sheets.
Pressure Unit Conversions
1 bar = 100,000 Pa = 100 kPa = 14.504 PSI = 0.9869 atm. Atmospheric pressure at sea level: 1 bar = 1013.25 mbar. Car tyre 2.5 bar = 250 kPa = 36.3 PSI. Blood pressure 120/80 mmHg = 16/10.7 kPa. Diving: +1 bar per 10 m depth.
Frequently Asked Questions (FAQ)
What is the difference between bar and atm?
1 atm (atmosphere) = 1.01325 bar — almost identical, but not equal. The atmosphere is the average air pressure at sea level; 1 bar is a round decimal value preferred in engineering. For most practical purposes they are interchangeable.
Why is blood pressure measured in mmHg rather than bar?
The unit mmHg (millimetres of mercury) originates from the era of mercury sphygmomanometers. One mmHg equals the pressure exerted by a 1 mm column of mercury = 133.3 Pa. The unit has persisted in medicine to this day.
What is gauge pressure and when do I need absolute pressure?
Gauge pressure measures relative to ambient atmospheric pressure — tyre pressure and gas pipes work with gauge pressure. Absolute pressure measures relative to a perfect vacuum. For thermodynamic calculations (gas density, equations of state) always use absolute pressure.
