A vacuum conversion chart is a vital tool for engineers, technicians, and industrial professionals who need to translate pressure measurements across different units with precision. From Torr and Pascal to bars and inches of mercury, understanding these conversions ensures accurate readings and optimal equipment performance.
In this article, we present a comprehensive vacuum conversion chart designed specifically for engineering and industrial applications helping you save time, reduce errors, and maintain consistency in your vacuum system operations.
Understanding Vacuum Measurement
What is Vacuum Suction Force?
Vacuum suction force is created by the difference in pressure between the outside air (ambient atmosphere) and the lower pressure inside a suction cup.
- The cup doesn’t “pull” the object; instead, the higher ambient air pressure pushes the object into the cup because the internal pressure is lower.
How to Calculate Vacuum Force
The basic formula used is:
F=P×AF = P \times AF=P×A
Where:
- F = holding (suction) force in Newtons (N)
- P = pressure difference (ambient minus vacuum) in Pascals (Pa)
- A = effective contact area of the suction cup in square meters (m²)
This formula helps estimate how much force a suction cup can generate based on the vacuum level and cup size.
Factors Affecting Vacuum Measurement
- Workpiece properties:
- Surface condition (smooth or rough)
- Material type and porosity.
- Contamination (dust, oil, etc.)
- These affect how well the cup seals and the effective vacuum.
- Dynamic factors:
- Movement or acceleration.
- Orientation (horizontal vs vertical).
- Safety margins for rough or porous surfaces.
- Vacuum level vs. performance:
- A vacuum must stay strong under load to safely hold objects.
- Measurements should reflect real operating conditions, not just ideal lab conditions.
Selecting the Right Suction Cup
- After measuring vacuum and knowing the cup’s area and load conditions, compare the calculated holding force to the actual application requirements.
- Choose a suction cup that can handle the required force with a safe margin, considering environmental and operational factors.
Common Vacuum Pressure Units
- Pascal (Pa)
- SI unit of pressure.
- 1 Pa = 1 Newton per square meter.
- Widely used in science and engineering.
- Millibar (mbar) / Hectopascal (hPa)
- Often used in meteorology and vacuum packaging.
- 1 mbar = 100 Pa.
- Torr / mmHg
- Common in labs and vacuum gauges.
- 1 Torr = 1 mmHg = 133.322 Pa.
- inHg (Inches of Mercury)
- Used in the imperial system, HVAC or automotive.
- 1 inHg = 3386 Pa.
- psi (Pounds per Square Inch)
- Popular in U.S. industrial applications.
- 1 psi = 6.895 kPa = 6895 Pa.
- Atmosphere (atm / at)
- Reference to atmospheric pressure.
- 1 atm = 101.325 kPa.
- 1 technical atmosphere (at) = 98.067 kPa.
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Understanding Vacuum Readings
- Absolute Pressure: Measured from zero (perfect vacuum). Always positive.
- Gauge Pressure: Measured relative to atmospheric pressure. Can be negative if below ambient.
- Percentage Vacuum: Shows how much of the atmospheric pressure has been removed.
Example:
- “-600 mbar” gauge pressure → absolute pressure = 1000 – 600 = 400 mbar (if atmospheric pressure = 1000 mbar).
- “60% vacuum” → 60% of atmospheric pressure removed → absolute pressure ≈ 400 mbar at sea level.
This understanding is crucial for calibrating sensors, reading gauges accurately, and ensuring safe vacuum operation.
Principles of Vacuum Conversion
- Understand the Units
Vacuum can be expressed in many units: Pa, mbar, Torr, psi, inHg, atm, or micron.
- SI unit: Pascal (Pa) – standard for scientific and engineering work.
- Other units are often used for specific industries, like psi in the U.S. industry or Torr in labs.
- Know the Type of Pressure
- Absolute Pressure: Measured from a perfect vacuum. Always positive.
- Gauge Pressure: Measured relative to atmospheric pressure; can be negative if below ambient.
- Percentage Vacuum: Shows the fraction of atmospheric pressure removed.
Conversion depends on which type of pressure you’re measuring.
- Use the Correct Conversion Factor
Each unit has a fixed relationship to Pascal:
- 1 bar = 100,000 Pa
- 1 Torr = 133.322 Pa
- 1 psi = 6,894.76 Pa
- 1 inHg = 3,386.39 Pa
- 1 micron = 0.133322 Pa
Rule: Multiply the measured value by the conversion factor to get Pascals.
- Account for Atmospheric Pressure if Needed
When measuring or calculating vacuum, consider the local atmospheric pressure if using gauge or percentage vacuum. This ensures accurate readings and proper system performance, especially when converting between absolute and relative vacuum values.
- Maintain Consistency
Always use the same units and measurement methods throughout your system or calculations. Consistent measurements prevent errors, ensure accurate comparisons, and make system design, monitoring, and calibration more reliable.
Comprehensive Vacuum Conversion Chart
This chart shows how different vacuum percentages relate to absolute pressure values in various units, such as Torr (mm Hg), micron, psi (absolute), inches of mercury (absolute and gauge), and kilopascals (kPa).
It helps users easily compare and convert vacuum levels for use in manufacturing, packaging, laboratory testing, and field service applications.
| % 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 |
Note:
This chart converts percentage vacuum into absolute pressure. It’s useful for configuring and calibrating vacuum systems, ensuring accuracy in design, testing, and operation.
Tools and Resources for Conversion
- Conversion Charts and Tables
These charts show common vacuum units like Pa, psi, Torr, inHg, mbar, and micron, along with their equivalents in Pascals (Pa). They’re handy for quickly checking values when designing systems, calibrating equipment, or operating vacuum devices. You’ll often find them in engineering manuals, lab handbooks, and vacuum equipment datasheets.
- Online Calculators and Apps
Many websites and mobile apps allow automatic unit conversion. Features may include:
- Converting between gauge, absolute, and percentage vacuum.
- Instant calculations for multiple units.
- Built-in formulas for pressure-area-force relationships.
Ideal for field use or when working with multiple unit systems.
- Engineering Software
Design and simulation tools often require vacuum values in SI units, such as pascals (Pa). Programs like CAD, FEA, or vacuum system design software typically include built-in conversion features to ensure calculations are accurate and systems operate correctly.
- Vacuum Measurement Instruments
These devices measure and display vacuum levels in a system. Many gauges and controllers can show readings in different units, such as Pa, Torr, mbar, psi, or inHg. Digital vacuum meters often let users switch between units easily, making real-time monitoring and calibration more convenient.
- Reference Books and Technical Manuals
Engineering handbooks, vacuum technology textbooks, and industrial equipment manuals provide:
- Unit conversion tables.
- Formulas for absolute, gauge, and percentage vacuum.
- Application-specific guidance.
A combination of charts, calculators, software, and instruments ensures accurate vacuum for safe operation across industries.
