Pressure Converter
Enter a value, select the source unit — get all conversions instantly with full working
1 atm = 101,325 Pa = 14.696 PSI = 1.01325 bar = 760 mmHg — see the full table below.All Conversions
Summary
Step-by-Step Calculation
Context & Real-World Reference
Key Conversions at a Glance
Full Details
Complete Pressure Conversion Table — All Units to All Units
Reference matrix: every unit converted to every other unit, based on exact SI definitions
What Is Pressure? Units, Formulas & Real-World Applications Explained
From pascals to PSI — the physics, definitions, and everyday uses of pressure measurement
Pressure is defined as the force applied perpendicular to a surface per unit area. The SI formula is P = F/A, where P is pressure in pascals (Pa), F is force in newtons (N), and A is area in square metres (m²). So 1 pascal = 1 newton per square metre = 1 N/m².
Because many industries evolved independently, pressure is measured in dozens of different units globally. PSI (pounds per square inch) dominates in the US for tyres, hydraulics, and plumbing. Bar and millibar (hPa) are standard in European meteorology and engineering. mmHg (millimetres of mercury) is universal for blood pressure and some medical applications. Pascal and kilopascal (kPa) are the international SI standard used in science and increasingly in automotive.
Complete Pressure Unit Reference — Definitions, Origins & Key Values
Every unit explained: what it is, where it comes from, and exactly how it relates to 1 ATM
| Unit | Symbol | Definition | = 1 atm | Primary Use |
|---|---|---|---|---|
| Pascal | Pa | SI base unit — 1 N/m² | 101,325 Pa | Science, engineering (SI standard) |
| Kilopascal | kPa | 1,000 Pa | 101.325 kPa | Automotive tyres, medical (some countries) |
| Megapascal | MPa | 1,000,000 Pa | 0.101325 MPa | Hydraulics, structural engineering |
| Bar | bar | 100,000 Pa exactly | 1.01325 bar | Europe: tyres, diving, meteorology |
| Millibar / hPa | mbar / hPa | 100 Pa = 0.001 bar | 1013.25 mbar | Meteorology, weather maps worldwide |
| PSI | psi | 1 lbf/in² = 6894.757 Pa | 14.6959 psi | US: tyres, hydraulics, industrial |
| Atmosphere | atm | 101,325 Pa exactly (defined) | 1 atm | Chemistry, diving, reference standard |
| mmHg / Torr | mmHg | 133.322 Pa | 760 mmHg | Blood pressure, medical, old barometry |
| Inches of Mercury | inHg | 3386.39 Pa | 29.9213 inHg | US aviation, US weather reports |
| Torr | torr | 101325/760 Pa = 133.322 Pa | 760 torr | Vacuum technology, lab science |
| cmH₂O | cmH₂O | 98.0665 Pa (at 4°C water) | 1033.23 cmH₂O | Medical (ventilators, IV pressure) |
Real-World Pressure Reference Guide — Tyre, Blood, Weather, Altitude & More
Practical pressure values you actually need, in every common unit
| Vehicle Type | PSI | bar | kPa | Notes |
|---|
| Category | Systolic (mmHg) | Diastolic (mmHg) | Systolic (kPa) | Diastolic (kPa) |
|---|
| Location | Altitude (m) | Pressure (kPa) | Pressure (hPa) | % of Sea Level |
|---|
Pressure Facts, Applications & Interesting Science
Everything from deep-sea crushing forces to the pressure inside a bicycle tyre
Why Tyre Pressure Matters
Under-inflated tyres by just 5 PSI (0.34 bar) can reduce fuel efficiency by up to 2%, increase tyre wear by 25%, and seriously compromise handling and braking distances. Tyres lose ~1 PSI per month naturally and ~1 PSI for every 10°F (5.6°C) drop in temperature. Always check cold.
Deep Ocean Pressure
Pressure increases by approximately 1 atm (101.325 kPa / 14.7 PSI) for every 10 metres of water depth. The Mariana Trench (Challenger Deep, ~11,000 m) has a pressure of about 1,100 atm = 111 MPa = 16,000 PSI — enough to crush unprotected submarines. Deep sea fish have evolved to withstand these extremes.
Aircraft Cabin Pressure
Commercial aircraft cabins are pressurised to the equivalent of 6,000–8,000 feet (1,800–2,400 m) altitude — about 75–82 kPa, or 0.74–0.81 atm. Lower than sea level pressure is used to reduce structural stress on the fuselage. This is why ears pop on takeoff and landing as pressure rapidly changes.
Blood Pressure Explained
Blood pressure readings are given as systolic/diastolic in mmHg. Systolic (~120 mmHg = 16 kPa) is peak pressure when the heart contracts. Diastolic (~80 mmHg = 10.7 kPa) is minimum pressure between beats. The "120/80" standard is a gauge pressure above atmospheric. Mercury sphygmomanometers defined these numbers historically.
Hydraulic Systems
Hydraulic machinery operates at very high pressures — typically 70–350 bar (1,000–5,000 PSI). Excavators and industrial presses can exceed 700 bar (10,000 PSI). Pascal's Law explains why: pressure applied to an enclosed fluid transmits equally in all directions, allowing enormous mechanical advantage with small actuators.
Pressure & Phase Changes
Pressure dramatically affects boiling and freezing points. Water boils at 100°C at 1 atm but only ~71°C at 5,000 m altitude (0.54 atm). A pressure cooker at ~15 PSI gauge (2 atm absolute) raises the boiling point to ~121°C, cutting cooking times significantly. Ice can be melted under extreme pressure — this lubricates ice skate blades.
Weather & Pressure Systems
Meteorologists track pressure in hPa (hectopascal = millibar). Standard is 1013.25 hPa. A deep storm system can drop below 950 hPa — each millibar below 1000 corresponds to increasing storm intensity. Hurricane records: Typhoon Tip (1979) reached 870 hPa. High pressure anticyclones bring clear, settled weather, typically 1025–1040 hPa.
Extreme Pressure Records
The highest sustained laboratory pressure ever achieved was approximately 770 GPa (7.7 million atm) using a diamond anvil cell — enough to turn hydrogen metallic. The lowest pressure in deep space is roughly 10⁻¹⁷ Pa, compared to the best laboratory vacuum of ~10⁻¹¹ Pa. Earth's atmospheric pressure at sea level sits in the middle of this extraordinary range.
How to Use This Pressure Converter — All 5 Modes Explained
Full guide to every mode with examples and use cases
- 1
Convert Mode — Full 11-Unit Conversion in One Click
Enter any pressure value, select the source unit from the dropdown, and get immediate conversions to all 11 units: PSI, bar, Pa, kPa, MPa, atm, mmHg, inHg, torr, mbar and cmH₂O. A visual pressure gauge shows where your value sits relative to atmospheric pressure. Full step-by-step multiplication working is shown with the exact conversion factor used.
- 2
Tyre Mode — Live PSI ↔ bar ↔ kPa Tri-Way Converter
Type into any of the three fields (PSI, bar or kPa) and the other two update instantly without pressing any button. Shows where the entered pressure falls in the recommended tyre pressure range for common vehicle types. Includes warnings for under- or over-inflation and a full tyre pressure reference table for cars, SUVs, trucks, motorcycles and bicycles.
- 3
Blood Pressure Mode — mmHg to kPa with WHO Category
Enter systolic and diastolic values in the standard mmHg format (e.g. 120/80) to convert both readings to kPa, Pa, and bar. The calculator also identifies the WHO blood pressure category (Normal, Elevated, High Stage 1, High Stage 2, or Hypertensive Crisis) and provides clinical context. Useful for medical students or international reference.
- 4
Altitude Mode — Pressure at Any Elevation
Enter an altitude in metres, feet or kilometres to calculate the estimated atmospheric pressure at that elevation using the International Standard Atmosphere (ISA) barometric formula. Shows pressure in kPa, hPa, atm, mmHg and PSI, along with what percentage of sea-level pressure remains. Useful for aviation, mountaineering, and weather correction.
- 5
Weather Mode — hPa ↔ inHg ↔ mmHg ↔ kPa
Enter a barometric pressure reading in hPa/mbar, inHg, mmHg or kPa and convert to all weather-relevant units instantly. Shows the weather classification (Deep Low, Low, Normal, High, Very High) and what conditions are typically associated with that pressure level. Includes the complete sea-level reference standard for each unit.
Pressure Converter — Frequently Asked Questions
Expert answers to the most searched pressure conversion questions