KPI's are very simple and easy when you know, why you want to track and improve the performance of 'x' thing.
knowing that 'x' thing is very important here because it makes impact on the overall performance of the business and its objective.
Giving an Example on what can be a KPI
Concrete cubes are failing - it will have impact on the business so you are making efforts in eliminating the causes and making it perform well so your management wats to track its performance to keep you motivated on this objective stating, cube should not have failures.
now this objective becomes a task for you and you make effort to achieve it and ultimately as per the review period you are giving the status of it as KPI.
So KPI is - No cube failure for poured concrete - here is the % you achieved (and this has huge amount of the efforts which you are taking which may not be known to the top management but they are really interested in knowing the achieved figure which shows the performance of all efforts in a single line).
For RMC Industry - Business has a issue of Transit mixers getting rejected when delivered at site and this requires additional space to disposing the rejected concrete - this scenario making lot of business loss and well as brand value damages, not this thing is turned into a KPI.
So to achieve this KPI, one need to take huge amount of the efforts in auditing everything and formulating processes to control it and then you see everything in one line report on KPI dashboard.
Concrete Acceptance Rate - Target for this month - more than 95% - result says Great you achieved 99.98%. here improved performance observation makes management to make even bigger target so next month you need to assure at least 96% delivery should be directly accepted by the clients.
I hope above examples help you in understanding KPI's
some of the general KPI's for QMS
Material Rejection rate should be less than 5% (if you see more, then its time to black list the bad performing suppliers).
Product Quality Rating - should have score more than x%
WIR clearances in 1 inspection - x%
Number of NCR should be less than x nos
Number of defects should be less than x nos
Cost of poor quality should be less than x amount
Deviation in the concrete floor top level should be within x mm
Verticality of the structure should be with x mm.
deviations in the opening sizes within x mm.
there are lot of thing which can become KPI unless you have clear understanding about the expected performance out of it.