A vacuum conversion chart is an essential reference for engineers, technicians, and manufacturers who work with vacuum systems and need accurate pressure unit conversions. Whether you’re measuring vacuum levels in Torr, Pascal, bar, or inches of mercury, having a free vacuum conversion chart on hand simplifies calculations and minimizes costly errors.
In this article, we’ll provide a downloadable chart, explain how to use it effectively, and explore why understanding these conversions is important for maintaining precision in industrial and laboratory applications.
Common Pressure Units in Vacuum Measurement
These include:
- Pascal (Pa): The SI unit of pressure; 1 Pa = 1 N/m².
- Millibar (mbar) / Hectopascal (hPa): Metric units often used in meteorology and vacuum packaging; 1 mbar = 100 Pa.
- Torr / mmHg: Used in laboratories and vacuum gauges; 1 Torr = 1 mmHg = 133.322 Pa.
- inHg (Inches of Mercury): Common in North America, especially for HVAC and automotive systems; 1 inHg = 3,386 Pa.
- psi (Pounds per Square Inch): Widely used in U.S. industries; 1 psi = 6.895 kPa = 6,895 Pa.
- atm / at (Atmospheres): Represent atmospheric pressure; 1 atm = 101.325 kPa, 1 technical atm = 98.067 kPa.
These units help compare, calculate, and calibrate vacuum levels accurately across scientific, industrial, and engineering applications.
Understanding Absolute, Relative, and Percentage Vacuum
To avoid confusion when measuring vacuum, it’s important to know the difference between absolute pressure, gauge pressure, and percentage vacuum.
- Absolute Pressure (abs)
Absolute pressure is the total pressure measured from a perfect vacuum (0 Pa). It is always a positive value because it measures pressure relative to a complete vacuum.
- Gauge Pressure
Gauge pressure measures pressure relative to the surrounding air (atmospheric pressure). It can be negative when the pressure inside a system is lower than the outside air.
- Percentage Vacuum
This shows how much air or pressure has been removed compared to the normal atmospheric pressure.
- For example, a 60% vacuum means 60% of the air has been removed, and 40% of the pressure remains.
Common Misunderstandings
A frequent mistake is confusing negative gauge pressure with absolute pressure.
Example 1:
- A reading of –600 mbar doesn’t mean the pressure is 600 mbar absolute.
- It means the pressure is 600 mbar lower than the surrounding air pressure.
- If atmospheric pressure is 1000 mbar, the actual absolute pressure is 400 mbar.
Example 2:
- A “60% vacuum” means 60% of the air has been removed.
- At sea level (≈1000 mbar), this equals about 400 mbar absolute pressure.
Understanding these distinctions ensures your measurements are correct and your vacuum systems work safely.
Free Vacuum Conversion Chart
A Free Vacuum Conversion Chart gives simple, easy-to-use reference values for converting between different vacuum pressure units, such as pascals (Pa), millibar (mbar), Torr, pounds per square inch (psi), inches of mercury (inHg), kilopascals (kPa), and percentage vacuum (%).
| % Vacuum | Torr (mm Hg) | Micron | psia (lb/in² abs) | Inches Mercury Absolute | Inches Mercury Gauge | kPa abs |
| 0.0 | 760.0 | 760,000 | 14.7 | 29.92 | 0.00 | 101.4 |
| 1.3 | 750.0 | 750,000 | 14.5 | 29.5 | 0.42 | 99.9 |
| 1.9 | 735.6 | 735,600 | 14.2 | 28.9 | 1.02 | 97.7 |
| 7.9 | 700.0 | 700,000 | 13.5 | 27.6 | 2.32 | 93.5 |
| 21.0 | 600.0 | 600,000 | 11.6 | 23.6 | 6.32 | 79.9 |
| 34.0 | 500.0 | 500,000 | 9.7 | 19.7 | 10.22 | 66.7 |
| 47.0 | 400.0 | 400,000 | 7.7 | 15.7 | 14.22 | 53.2 |
| 50.0 | 380.0 | 380,000 | 7.3 | 15.0 | 14.92 | 50.8 |
| 61.0 | 300.0 | 300,000 | 5.8 | 11.8 | 18.12 | 40.0 |
| 74.0 | 200.0 | 200,000 | 3.9 | 7.85 | 22.07 | 26.6 |
| 87.0 | 100.0 | 100,000 | 1.93 | 3.94 | 25.98 | 13.3 |
| 88.0 | 90.0 | 90,000 | 1.74 | 3.54 | 26.38 | 12.0 |
| 89.5 | 80.0 | 80,000 | 1.55 | 3.15 | 26.77 | 10.7 |
| 90.8 | 70.0 | 70,000 | 1.35 | 2.76 | 27.16 | 9.3 |
| 92.1 | 60.0 | 60,000 | 1.16 | 2.36 | 27.56 | 8.0 |
| 93.0 | 51.7 | 51,700 | 1.00 | 2.03 | 27.89 | 6.9 |
| 93.5 | 50.0 | 50,000 | 0.97 | 1.97 | 27.95 | 6.7 |
| 94.8 | 40.0 | 40,000 | 0.77 | 1.57 | 28.35 | 5.3 |
| 96.1 | 30.0 | 30,000 | 0.58 | 1.18 | 28.74 | 4.0 |
| 96.6 | 25.4 | 25,400 | 0.49 | 1.00 | 28.92 | 3.4 |
| 97.4 | 20.0 | 20,000 | 0.39 | 0.785 | 29.14 | 2.7 |
| 98.7 | 10.0 | 10,000 | 0.193 | 0.394 | 29.53 | 1.3 |
| 99.0 | 7.6 | 7,600 | 0.147 | 0.299 | 29.62 | 1.0 |
| 99.87 | 1.0 | 1,000 | 0.01934 | 0.03937 | 29.88 | 0.13 |
| 99.90 | 0.75 | 750 | 0.0145 | 0.0295 | 29.89 | 0.1 |
| 99.99 | 0.10 | 100 | 0.00193 | 0.00394 | 29.916 | 0.013 |
| 99.999 | 0.01 | 10 | 0.000193 | 0.000394 | 29.9196 | 0.0013 |
| 100 | 0.00 | 0 | 0 | 0.00 | 29.92 | 0 |
Notes:
- Converts percentage vacuum into absolute pressure in multiple units.
- Useful for calibrating vacuum sensors, sizing suction cups, or configuring vacuum systems.
- Helps avoid confusion between gauge, absolute, and percentage vacuum readings.
See also: Why Do Electronics Need Surge Protection?
How to Use the Conversion Chart
Using a vacuum conversion chart helps you easily convert between different pressure units so that your readings are consistent and accurate. Follow these simple steps:
- Find Your Starting Unit
Start by identifying the unit your vacuum gauge, sensor, or system uses. For example, psi, inHg, Torr, or mbar. Different devices and industries use different units, depending on where or how they’re used.
- Locate the Conversion Factor
To convert a vacuum or pressure reading to another unit, first find the conversion factor in a conversion chart. This factor tells you how to translate your current unit (like Torr, psi, or mbar) into the desired unit (commonly Pascals, Pa).
Common conversion factors include:
- 1 bar = 100,000 Pa
- 1 Torr = 133.322 Pa
- 1 psi = 6,894.76 Pa
- 1 inHg = 3,386.39 Pa
Multiply your measurement by the conversion factor to get the value in the new unit.
- Convert the Value
Once you know the conversion factor, multiply your pressure reading by it to get the equivalent value in Pascals (or your desired unit).
- Apply the Result
Now that you’ve converted your pressure value, use it in your work. The converted value can be used for:
- Calibrating sensors to ensure accurate readings
- Setting control parameters in vacuum systems
- Comparing equipment specifications from different manufacturers
- Performing engineering or simulation calculations that require SI units
By following these steps, you ensure that all measurements are consistent across different tools, systems, and international standards. This helps avoid mistakes, improves accuracy, and keeps your data reliable.
Why Vacuum Unit Conversion Matters
Vacuum unit conversion is essential because different industries and instruments use different pressure units, and accurate conversions ensure consistent, reliable measurements.
Here’s why it matters:
- Ensures Accurate Communication
In vacuum measurements, professionals often use different pressure units such as Pa, Torr, mbar, or psi. Converting these values to a common standard unit like Pascal (Pa) ensures that everyone interprets data the same way. This prevents misunderstandings, calculation errors, and costly mistakes in design, testing, and operation.
- Improves System Calibration
Many vacuum sensors, controllers, and gauges require inputs in specific units. Correct conversion ensures your equipment is properly calibrated and operates safely.
- Standardizes International Projects
Global industries use both metric and imperial systems. Converting units keeps data, specifications, and reports consistent across borders.
- Enables Accurate Design and Simulation
When designing vacuum systems or running simulations, incorrect unit conversions can lead to errors in performance calculations or safety margins.
- Prevents Equipment Damage or Misinterpretation
Misreading a unit can result in incorrect vacuum levels, poor system performance, or even damage.
Vacuum unit conversion ensures accuracy, safety, and consistency in all stages of measurement, from design to operation.
