Leak Rate Calculator & Unit Converter
A leak rate expresses the amount of gas escaping over time. Calculate a pressure-decay leak rate or convert between common standard-volume and pressure-volume units below.
Results use a standard reference pressure of 1 atmosphere (1013.25 mbar). They are engineering estimates, not a substitute for a validated production test method or specification.
Pressure-decay leak-rate calculator
Enter the measured pressure drop, enclosed test volume, and test time. The calculation keeps time units explicit: seconds are divided by 60 only when the selected unit is minutes.
Leak-rate unit converter
Pressure-decay formula and worked example
For a settled, enclosed volume, the calculator uses Qstd = ΔP × V ÷ (Pstd × Δt), where Qstd is standard volumetric flow, ΔP is pressure drop, V is test volume, Pstd is 1013.25 mbar, and Δt is the test time.
Example: 50 cc, 0.02 psi pressure drop, and 3 seconds (0.05 minutes): (0.02 psi × 50 cc) ÷ (14.7 psia × 0.05 min) = 1.36 sccm. This preserves the previous calculator’s published example while making the displayed seconds-to-minutes conversion explicit.
Leak-rate unit conversion table
| Unit | Equivalent to 1 sccm |
|---|---|
| sccm / cc/min | 1 |
| cc/s | 0.0166667 |
| mL/min | 1 |
| mbar·L/s | 0.0168875 |
| Pa·m³/s | 0.00168875 |
| atm·cc/s | 0.0166667 |
| L/h | 0.06 |
Which leak-rate unit should I use?
Use the unit named by your drawing, customer requirement, tester program, or governing procedure. In US manufacturing air testing, sccm and cc/min are common. In European and vacuum contexts, mbar·L/s is common. Pa·m³/s is the SI pressure-volume-flow expression. Unit selection alone does not define an acceptable leak: document the reference conditions, gas, volume, temperature, and method.
Assumptions and limits
- The gas behavior is treated as ideal and the measured system is isothermal during the test interval.
- The part and fixture have completed their settle period; thermal drift, material expansion, and fixture leakage can affect a pressure-decay result.
- “Standard” volume is referenced here to 1 atm (1013.25 mbar). If a contract specifies another standard temperature or pressure, use that requirement.
Learn about leak-test methods and equipment
Read about pressure-decay testing, leak-test fixtures, mass-flow testing, and peer trace-gas leak testing for helium leak-rate work. Compare air leak testers or review the Z-Charge and Z-Ion trace-gas system.
Leak-rate calculator FAQ
What does sccm mean?
SCCM means standard cubic centimeters per minute: a volume-flow rate referenced to defined standard conditions.
Is cc/min the same as sccm?
They are commonly used interchangeably only when cc/min is explicitly referenced to the same standard conditions. This page uses 1 atm (1013.25 mbar).
How do I convert mbar·L/s to Pa·m³/s?
Multiply by 0.1. For example, 1 mbar·L/s equals 0.1 Pa·m³/s.
Why does pressure-decay testing need a settle time?
Settling helps reduce apparent pressure changes caused by temperature change, material relaxation, or fixture movement before the measured test interval.
Can this calculator set my production reject limit?
No. Set a reject limit through your product requirement and a validated test process; use the calculator as a transparent engineering conversion aid.
See the leak-testing glossary for units and measurement definitions.
