Air Pressure Calculator
Convert air pressure between hPa, mBar, inHg, mmHg (Torr), and atm. Fill in any one value and click Calculate to convert to all other units. See also our Pressure Converter and Weather Calculators.
Enter the value that you want to calculate air pressure.
Fill in the value of the known unit and click on 'Calculate' to calculate the four unknown air pressure units.
Relationship Between Altitude and Pressure
| Altitude above Sea Level | Absolute Atmospheric Pressure | ||||
|---|---|---|---|---|---|
| feet | miles | meters | kPa | atm | psia |
| -5000 | -0.95 | -1524 | 121.0 | 1.19 | 17.55 |
| -4000 | -0.76 | -1219 | 116.9 | 1.15 | 16.95 |
| -3000 | -0.57 | -914 | 112.8 | 1.11 | 16.36 |
| -2000 | -0.38 | -610 | 108.9 | 1.07 | 15.79 |
| -1000 | -0.19 | -305 | 105.0 | 1.04 | 15.24 |
| -500 | -0.09 | -152 | 103.2 | 1.02 | 14.96 |
| 0 | 0.00 | 0 | 101.3 | 1.00 | 14.70 |
| 500 | 0.09 | 152 | 99.5 | 0.98 | 14.43 |
| 1000 | 0.19 | 305 | 97.7 | 0.96 | 14.17 |
| 1500 | 0.28 | 457 | 96.0 | 0.95 | 13.92 |
| 2000 | 0.38 | 610 | 94.2 | 0.93 | 13.66 |
| 2500 | 0.47 | 762 | 92.5 | 0.91 | 13.42 |
| 3000 | 0.57 | 914 | 90.8 | 0.90 | 13.17 |
| 3500 | 0.66 | 1067 | 89.1 | 0.88 | 12.93 |
| 4000 | 0.76 | 1219 | 87.5 | 0.86 | 12.69 |
| 4500 | 0.85 | 1372 | 85.9 | 0.85 | 12.46 |
| 5000 | 0.95 | 1524 | 84.3 | 0.83 | 12.23 |
| 6000 | 1.14 | 1829 | 81.2 | 0.80 | 11.78 |
| 7000 | 1.33 | 2134 | 78.2 | 0.77 | 11.34 |
| 8000 | 1.52 | 2438 | 75.3 | 0.74 | 10.92 |
| 9000 | 1.70 | 2743 | 72.4 | 0.71 | 10.51 |
| 10000 | 1.89 | 3048 | 69.7 | 0.69 | 10.11 |
| 15000 | 2.84 | 4572 | 57.2 | 0.56 | 8.29 |
| 20000 | 3.79 | 6096 | 46.6 | 0.46 | 6.75 |
| 25000 | 4.73 | 7620 | 37.6 | 0.37 | 5.45 |
| 30000 | 5.68 | 9144 | 30.1 | 0.30 | 4.36 |
| 35000 | 6.63 | 10668 | 23.8 | 0.24 | 3.46 |
| 40000 | 7.58 | 12192 | 18.8 | 0.19 | 2.72 |
| 45000 | 8.52 | 13716 | 14.7 | 0.15 | 2.14 |
| 50000 | 9.47 | 15240 | 11.6 | 0.11 | 1.68 |
| 55000 | 10.42 | 16764 | 9.1 | 0.09 | 1.32 |
| 60000 | 11.36 | 18288 | 7.2 | 0.07 | 1.04 |
| 65000 | 12.31 | 19812 | 5.6 | 0.06 | 0.82 |
How to Calculate Air Pressure
- Enter the known pressure value in any one of the five input fields (hPa, mBar, inHg, mmHg, or atm).
- Click the Calculate button to convert to all other pressure units.
- All four remaining fields will be automatically filled with the converted values.
- To convert a different value, clear the fields and enter a new number in any field.
- Refer to the altitude-pressure table above for standard atmospheric pressure at various elevations.
Air Pressure Conversion Formula
Air Pressure Unit Conversions:
Standard Atmosphere (sea level):
1 atm = 101,325 Pa = 1013.25 hPa = 1013.25 mbar
1 atm = 760 mmHg (Torr) = 29.9212 inHg
1 atm = 14.696 psi
Conversion Factors:
1 hPa = 1 mbar = 100 Pa
1 inHg = 33.8639 hPa = 25.4 mmHg
1 mmHg = 1 Torr = 133.322 Pa
1 atm = 101,325 Pa
Barometric Formula (pressure at altitude):
P = P₀ × (1 - Lh/T₀)^(gM/RL)
Approximate rule:
Pressure drops ~1 hPa per 8.5 meters altitude
Pressure drops ~1 inHg per 1000 feet altitudeExample Conversion
Problem: Convert 29.92 inHg to all other pressure units.
Given: Pressure = 29.92 inHg (standard sea level)
Solution:
• To hPa: 29.92 × 33.8639 = 1013.25 hPa
• To mBar: 1013.25 mbar (same as hPa)
• To mmHg: 29.92 × 25.4 = 760.0 mmHg
• To atm: 29.92 / 29.9212 = 1.000 atm
Answer: 29.92 inHg = 1013.25 hPa = 1013.25 mbar = 760 mmHg = 1 atm
Technical Details
Atmospheric pressure is the force exerted by the weight of air in the atmosphere above a given point. At sea level, the standard atmosphere exerts a pressure of 101,325 pascals (1013.25 hPa), equivalent to the weight of a mercury column 760 mm high. This is why mmHg and inHg are traditional pressure units — they originate from mercury barometer measurements invented by Evangelista Torricelli in 1643.
In meteorology, pressure is reported in hectopascals (hPa) or millibars (mbar) — these are identical units. Aviation uses inches of mercury (inHg) for altimeter settings in the US and hPa internationally. Weather maps show isobars (lines of equal pressure) typically ranging from 960 to 1050 hPa. Low pressure systems (below 1013 hPa) bring clouds and precipitation, while high pressure systems (above 1013 hPa) bring clear skies.
Air Pressure Unit Reference Table
| Unit | Symbol | 1 atm equals | Used in |
|---|---|---|---|
| Hectopascal | hPa | 1013.25 | Meteorology (international) |
| Millibar | mbar | 1013.25 | Meteorology (older notation) |
| Inches of Mercury | inHg | 29.9212 | Aviation (US), weather reports |
| Millimeters of Mercury | mmHg | 760 | Medicine (blood pressure) |
| Atmosphere | atm | 1 | Chemistry, physics reference |
| Pascal | Pa | 101,325 | SI standard unit |
| Kilopascal | kPa | 101.325 | Engineering, tire pressure |
| PSI | psi | 14.696 | US engineering, tire pressure |
Frequently Asked Questions
What is atmospheric pressure at sea level?
Standard atmospheric pressure at sea level is 101.325 kPa = 1 atm = 14.696 psi = 760 mmHg = 1013.25 mbar = 29.92 inHg.
What is the difference between hPa and mbar?
Hectopascal (hPa) and millibar (mbar) are exactly the same unit: 1 hPa = 1 mbar = 100 Pa. The World Meteorological Organization adopted hPa as the standard.
How much does pressure decrease per 1000 feet?
Pressure decreases approximately 1 inHg (33.86 hPa) per 1,000 feet of altitude gain near sea level. The rate decreases at higher altitudes.
Why is mmHg used for blood pressure?
Blood pressure is measured in mmHg because early sphygmomanometers used mercury columns. A reading of 120/80 mmHg means systolic pressure equals 120 mm of mercury column height.
What pressure units do pilots use?
In the US, pilots use inches of mercury (inHg) for altimeter settings. Internationally, hectopascals (hPa) are used. Standard setting is 29.92 inHg or 1013.25 hPa.
Objective of Measurement:
Measurement is the most important aspect of our life. We use measurement in science, engineering, business trading, personal life, education, and more other fields. As technology is growing day by day so we need a highly accurate and easy convenient global measuring system in each and every field. It is essential to use standard measurement in every field that everyone to be sure that they not get cheated.
History of Measurement:
In history for measurement people used the human body as a tool. For measuring length used forearm, hand, foot & finger as a unit. The foot, finger is a subdivided shorter unit of a length. This type of measurement is not accurate cause different in size of the arm & finger for different people & some of the countries still using it. In history, there were lots of measuring systems developed but mostly used imperial, the metric system of measurement. We use these systems for measure distances, volume, weight, speed, area etc. Due to this a major problem everyone is facing while doing trading between the countries. A huge improvement in civilization, It necessary to improve measuring standards. Nowadays International Standard (SI) units are used as a global measurement system.
Air Pressure Calculator - Unit Converter:
Our air pressure calculator converts between hectopascal (hPa), millibar (mbar), inches of mercury (inHg), millimeters of mercury (mmHg/Torr), and atmosphere (atm) vice versa with metric conversion. It also provides a comprehensive altitude-pressure reference table showing atmospheric pressure at various elevations from -5000 to 65000 feet.
Air pressure conversions & its abbreviations
| Unit | Abbreviation | Unit | Abbreviation |
|---|---|---|---|
| hectopascal | hPa | millibar | mbar |
| inches of mercury | inHg | millimeters of mercury | mmHg |
| atmosphere | atm | pascal | Pa |
| kilopascal | kPa | pound per square inch | psi |
| bar | bar | torr | Torr |