Pressure Converter — PSI, Bar, kPa, atm & mmHg Explained
Learn how pressure units like PSI, bar, kPa, atm, and mmHg relate to each other — with real examples for tyres, weather, blood pressure, and industrial systems, plus a free pressure converter.
By sadiqbd · June 6, 2026
Pressure is measured in more units than almost any other quantity
Pascal. Bar. PSI. ATM. mmHg. Torr. Millibar. Depending on whether you're checking tyre pressure, reading a weather forecast, calibrating industrial equipment, or working with medical devices, you'll encounter a different unit every time. None of them are intuitively comparable without conversion.
A pressure converter eliminates the translation problem. Whether you're inflating tyres, reading a barometric pressure reading, or interpreting a hydraulic system spec, it gives you the number in whatever unit you need.
The Main Pressure Units
Pressure is force per unit area. The SI unit is the pascal (Pa) — one newton per square metre. Because the pascal is small, most practical applications use multiples.
| Unit | Abbreviation | Equivalent in Pa |
|---|---|---|
| Pascal | Pa | 1 Pa |
| Kilopascal | kPa | 1,000 Pa |
| Megapascal | MPa | 1,000,000 Pa |
| Bar | bar | 100,000 Pa |
| Millibar | mbar | 100 Pa |
| Atmosphere | atm | 101,325 Pa |
| PSI (pound per sq inch) | psi | 6,894.76 Pa |
| Torr / mmHg | Torr | 133.32 Pa |
| inHg (inches of mercury) | inHg | 3,386.39 Pa |
How to Use the Pressure Converter on sadiqbd.com
- Enter the pressure value.
- Select the source unit — PSI, bar, kPa, atm, mmHg, etc.
- Select the target unit.
- Read the result — instant.
Real-World Examples
Tyre pressure
Most passenger car tyres are inflated to 30–35 PSI. A car manual might list recommended pressure as 2.2 bar or 220 kPa.
- 32 PSI × 0.0689 = 2.21 bar ✓
- 32 PSI × 6.895 = 220.6 kPa ✓
All three are saying the same thing. If your tyre gauge reads in PSI but your car manual says bar, or vice versa — use the converter to confirm you're at the right pressure.
Weather and atmospheric pressure
Standard atmospheric pressure = 1 atm = 101.325 kPa = 1013.25 mbar = 760 mmHg.
A weather app showing 1008 mbar is reporting slightly below standard pressure — typical of low-pressure weather systems. In PSI: 1008 mbar ÷ 68.95 = 14.62 PSI. In kPa: 1008 × 0.1 = 100.8 kPa.
Meteorologists use millibars (mbar) or hectopascals (hPa) — the same thing numerically (1 hPa = 1 mbar = 100 Pa). Both are standard in weather reporting.
Blood pressure reading
A blood pressure of 120/80 mmHg is the clinical standard unit. In kPa:
- 120 mmHg × 0.1333 = 16 kPa (systolic)
- 80 mmHg × 0.1333 = 10.67 kPa (diastolic)
Medical devices worldwide use mmHg (or Torr, which is essentially the same) for blood pressure. The converter is useful when comparing devices or reading research papers that use different units.
Industrial hydraulic system
A hydraulic press operates at 250 bar. In PSI: 250 × 14.504 = 3,626 PSI
In MPa: 250 bar × 0.1 = 25 MPa
High-pressure industrial systems typically work in bar or MPa; American specifications often use PSI. The converter makes cross-referencing straightforward.
Scuba diving pressure
Water pressure increases by approximately 1 atm per 10 metres of depth. At 30 metres:
Total pressure = 1 (surface) + 3 (water) = 4 atm = 58.8 PSI = 405.3 kPa
This is why dive equipment is rated in bar (standard dive cylinders are filled to 200–300 bar = 2,900–4,350 PSI) and why pressure equalisation matters for divers.
Pressure Ranges in Context
| Application | Typical pressure |
|---|---|
| Human blood pressure (systolic) | 120 mmHg = 16 kPa = 2.3 PSI |
| Car tyre (passenger) | 30–35 PSI = 2.1–2.4 bar |
| Bicycle tyre (road) | 80–130 PSI = 5.5–9 bar |
| Standard atmosphere | 1 atm = 14.696 PSI = 101.3 kPa |
| Espresso machine | 9 bar = 130.5 PSI |
| Car engine oil | 25–65 PSI = 1.7–4.5 bar |
| Industrial hydraulics | 100–700 bar = 1,450–10,150 PSI |
| Deep ocean (10,000 m) | ~1,000 bar = 14,500 PSI |
Tips for Working With Pressure Units
Gauge pressure vs. absolute pressure. Many pressure measurements are "gauge" — measured relative to atmospheric pressure. Tyre pressure gauges read gauge pressure (so a reading of 0 PSI means tyre pressure equals atmospheric). Absolute pressure adds atmospheric pressure on top. Watch for "PSIg" (gauge) vs. "PSIa" (absolute) in technical specs.
For weather, use mbar or hPa. Millibars and hectopascals are numerically identical and are the standard for atmospheric pressure. Standard atmosphere = 1013.25 mbar. Anything below ~1000 mbar is a notable low-pressure system.
For medical use, mmHg is universal. Blood pressure, intraocular pressure, and many medical pressure measurements use mmHg. This is a legacy of mercury manometers and has stuck despite SI standardisation.
High-pressure specifications often use bar or MPa. For hydraulics, pneumatics, and industrial equipment, bar and MPa are the professional standard in most non-US contexts. PSI is common in US industrial specs.
Frequently Asked Questions
What is standard atmospheric pressure in different units? 1 atm = 101,325 Pa = 101.325 kPa = 1013.25 mbar = 14.696 PSI = 760 mmHg = 29.92 inHg = 1.01325 bar.
What's the difference between PSI and bar? Both measure pressure; they just use different scales. 1 bar = 14.504 PSI. For tyre pressure: 2.2 bar ≈ 32 PSI. Bar is metric and used internationally; PSI is imperial and dominant in the US.
Is mmHg the same as Torr? Almost exactly. 1 Torr = 1/760 of an atmosphere = 133.322 Pa. 1 mmHg = 133.322 Pa as well. The difference is negligible for practical purposes, and the terms are often used interchangeably in medical and scientific contexts.
What pressure unit do weather apps use? Most weather apps show pressure in mbar (millibars) or hPa (hectopascals) — same number, different name. Some apps in the US show inHg (inches of mercury).
Is the pressure converter free? Yes — free, instant, no sign-up.
Pressure units are one of those measurement categories where the variety is genuinely wide and conversions are rarely intuitive. The converter makes any translation a 5-second task, whether you're checking tyre pressure, reading a barometer, or interpreting an industrial specification.
Try the Pressure Converter free at sadiqbd.com — instant conversion between PSI, bar, kPa, atm, mmHg, and more.
