Pressure Converter
Convert pressure with Pascal as the universal base unit.
Enter Pressure and Units
Table of Contents
Complete Guide to Pressure Units
Pressure is force per unit area. The SI unit is the Pascal (Pa): one newton on one square meter. Engineers also use bar and psi, meteorologists use hectopascals (same numeric value as millibar), and medicine still references mmHg for blood pressure.
Common units at a glance
| Unit | Typical use | ≈ Pa |
|---|---|---|
| 1 atm | Standard atmosphere | 101325 |
| 1 bar | Industrial gauges | 100000 |
| 1 psi | US tires, hydraulics | 6894.76 |
| 760 mmHg | Sea-level mercury column | 101325 |
Gauge vs absolute pressure
Many tire and tank gauges read gauge pressure (relative to ambient air). Absolute pressure adds atmospheric pressure back. This converter works with the numeric value you enter - know which kind your instrument reports before comparing to specs.
Vacuum ratings sometimes appear as negative gauge pressure or as absolute pressure below 1 atm. Always confirm the datasheet convention.
Frequently asked questions
- Is bar the same as atm?
- Close but not identical. 1 bar = 100000 Pa while 1 atm = 101325 Pa. For rough tire checks the difference is small.
- What is psi used for?
- Pounds per square inch is common for US automotive, hydraulic and pneumatic equipment ratings.
- Why mmHg in medicine?
- Traditional mercury manometers defined the unit. Modern devices convert internally but still display mmHg in many regions.
- Can pressure be negative?
- Gauge pressure can read below ambient (vacuum). Absolute pressure cannot drop below zero in classical physics.
- What is kPa used for?
- Kilopascals appear on SI engineering drawings, weather charts (as hPa), and some digital tire pumps.
Pressure Conversion Formulas
Every unit maps to Pascals with a fixed factor. Multiply the input by factor(from) to get Pa, then divide by factor(to) for the result.
Example: 14.7 psi × 6894.757 Pa/psi ≈ 101325 Pa ≈ 1 atm. Small rounding differences appear if you use truncated constants.
Pro Tip:
When comparing tire pressure, stick to one unit on the gauge and label. Mixing bar and psi on the same log without converting causes slow leaks to be misread.
How to Convert Pressure
Enter the pressure value, choose the unit you have and the unit you need, then submit. For manual checks, convert to Pa first.
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1Enter the pressure reading from a gauge, datasheet or calculation.
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2Select From and To pressure units (Pa, bar, psi, etc.).
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3Click Convert Pressure to see the result.
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4Compare with a known reference (1 atm ≈ 101.325 kPa ≈ 14.696 psi) if the result looks off.
Quick sanity check:
Car tire labels often quote bar or psi. HVAC duct static pressure may be listed in inches of water column (not in this tool) or Pa.
Common Use Cases
Pressure units vary by industry. Pick the output unit that matches your spec sheet or local convention.
Automotive and tires
Passenger tire pressures are commonly quoted in psi in North America and in bar elsewhere.
Process and hydraulics
Plant equipment often uses bar or psi on nameplates; SI drawings may list kPa or MPa.
Weather and aviation
Surface maps use hectopascals (hPa), numerically equal to millibars. Altimeter settings may be in inHg in the US.
Medical
Blood pressure is traditionally reported in mmHg; kPa appears on some digital monitors.
Always confirm whether a spec is gauge or absolute before comparing converted values to safety limits.
Practical Examples
Worked conversions using the same Pascal factors as this calculator.
Example 11 atm to kPa
101325 / 1000 = 101.325 kPa
Example 232 psi to bar
32 × 6894.757 / 100000 ≈ 2.21 bar
Example 3120 mmHg to kPa
120 × 133.322 / 1000 ≈ 16.0 kPa
Example 42 bar to psi
2 × 100000 / 6894.757 ≈ 29.0 psi