Before calculating the defect leakage we have to understand that what defect leakage means.
What is Defect Leakage?
After the delivery of application or product or we can say after the release, if end user or Customer find any defect by using that application then it is called defect leakage, it is also called bug leakage.
How we calculate Defect Leakage?
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
If after release client found 9 defects, during the test, tester reported 201 defects and from these 20 defects were invalid
Defect Leakage = (9/201-20)*100=4.9%