Enter the volume, change in pressure, and time into the calculator to determine the leak rate.

Leak Rate Formula

The following formula is used to calculate a leak rate. This formula is based on the ideal gas law.

LR = (V*∆P) / ∆T

  • Where LR is the leak rate (ft-lbf/sec)
  • V is the volume of the part (ft^3)
  • ∆t is the time (seconds)
  • ∆P is the change in pressure or pressure loss (psf)

These are an example of the units for this calculation, but other units can be used.

Leak Rate Definition

A leak rate is defined as the rate of flow, or “leak”, of gas out of a container that is attempting to hold the gas.

Example

How to calculate leak rate?

First, determine the volume of the container that’s holding the gas. For this problem, the volume of the container is found to be 50 ft^3.

Next, determine the change in pressure, or the pressure difference, between the inside and outside of the container. In this case, the pressure difference is 100 lb-f/ft^2.

Next, measure the total time that the leak is occurring. In this example, the measured time is 25 seconds.

Finally, calculate the leak rate.

Using the formula above, the leak rate is found to be:

LR = (V*∆P) / ∆T

= 50 * 100/ 25

= 200 ft-lbf/sec