I have few doubts in the Defect leakage ratio calculation formula.

I found one of the formula to calculate as below: CD=No. of Defects raise by customer after release

DR=No. of Defects raised by Tester before release

ID- No. of invalid Defects from Defects raised by tester before release(Eg. Duplicate, CannotFix, error in test environment etc.)

Formula to calculate Defect Leakage Defect Leakage=(CD/DR-ID)*100

Here my doubt is related to the period to consider and catagery of bugs found.

Eg:- Release1 happened on April 27th 2018 and Release2 happened on Sep 24th 2018.

Now to calculate Defect leakage ratio for Release2: What duration has to consider?

For DR and ID, it is April 28th 2018 to Sep 24th 2018 and defected found internally in this duration. For CD whether needs to consider from Sep 25th 2018 to till current Date? Is won't be the Release2 Production leakage till next release whatever productions bugs raised. If yes, then when exactly the metric will be calculated?

Another doubt is, if one production bug raised after Sep 25th 2018(After Release2) and developer found the issue exists from the old releases say Release1 then whether needs to consider this bug in the Release2 defect leakage ratio?

Please clarify me?


The DLR for the current release is a changing metric that will increase over time until the release is closed.

The bug that was found by the customer in the latest release and reported by the tester in the previous release counts as a DR in the earlier release and a CD in the later release.

With that said, the Defect Leakage Ratio as a number isn't nearly as useful as a list of bugs found by the customer, per release. This list demonstrates the delta between what the company thought the customer wanted and what the customer actually wanted. It doesn't matter if the bug was found internally or not; if the customer finds it the customer cares about it at the company didn't understand the importance of that thing the customer finds significant. Such a list reviewed by Developers, Testers, PMs and Management on a regular basis is a customer feedback loop that helps the company build software that better aligns with the needs and wants of the customer. This list will help the company gain better customer focus than a mere ratio.

  • Thanks for the reply. One more doubt is this metric will be calculated for current release or previous release usually? CD will consider defects alone or production bugs found internally also will be considered? Dec 17 '18 at 6:03
  • CD is only for issues found by the customer. The ratio only becomes static once a release is no longer the current release. It can be useful to have a live running count of the DLR in the current release and a list of the ticket numbers and bug titles if your team intends to fix customer-reported issues as they come up. Dec 17 '18 at 13:40
  • One more small doubt, whether environment bugs raised by customer also considered or bugs which requires a code fix only considered for CD calculation? Dec 18 '18 at 5:48
  • 1
    Michael Bolton defines a bug as "Something that bugs someone who matters.". If the bug can (or ought to be) be fixed by a change in your product it counts. Example: Unable to connect to a third-party database. Your application might detect the problem and offer next steps for the customer to take. While not solving the customer's problem directly, you have solved the bug as best you can within your application by telling the customer what they should do next. Dec 18 '18 at 13:50
  • Hello @JerryPenner : Can you please clear me this point in this example. Ex. I have found a total of 80 issues in current build & after releasing the same build then client reports 20 issues. so what is the ratio of the defect leakage? Apr 27 '19 at 6:50

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