If you are referring to how long it usually takes to get a 0 tx fee transaction confirmed then it really depends on how long it has been since the inputs have last been spent. If enough bitcoin days are being destroyed (if you are spending enough bitcoin that has been long enough since the inputs were last transferred) then it should confirm within one or two blocks. If there are a large number of unconfirmed transactions and/or there happens to be a longer then normal time between blocks when you push your transaction then it make take somewhat longer