I have Dell 5000 series Inspiron 5547 i5, then what the exact specification for Ram upgrade. (buy on 2015).

The specs for the 5547 are DDR3L 1600 with total maximum of 16 GB (8 GB in each slot) so yes you can go 8 GB with 4 GB in each slot. Crucial page is here with that information.

I believe my post explains the RAM upgrade possibilities for your system. And if you click on the link to Crucial, they have all the particulars.

Again..

DDR3L 1600

2 SODIMM slots in your system

You can have 2 x 4 GB RAM modules for a total of 8 GB

You can have 2 x 8 GB RAM modules for a total of 16 GB

I've dell 5547. And there is 4gb ram in one slot. Can I install 8 gb ram in the other slot ? So that total will be 12 gb. Is that possible ?Or in the both slot I've to put same memory of ram ?

@JOcean 

Dell specs confirm that you can install 8 GB giving you a total of 12 GB. Keep in mind that you will only have dual channel on 8 GB of the 12 GB total. That is the 4 GB and 4 GB of the 8 GB RAM module. As always the best procedure is to buy a kit of RAM modules so in this case 2 x 8 GB matched RAM modules. That will give you the best compatibility with 16 GB of dual channel RAM.