How do i convert 12vdc 16A to 12vdc 5A using resistor ? Answered

What are you trying to do ? If the load wants 12V at 5A, then unless its LEDs, it will take what it wants UP to 5A, there is no need to "limit" the current.

I kind'of understand Your dilemma. You worry about that 16A to burn something in Your 5A device? Don't worry, just put a 5A fuse there to protect Your device in a case of an "owerload" in Your device,(short, misleaded power-rail, bad ground etc...).

By understanding how Ohms law works.
In your case you would not be converting but limiting the current - with a voltage on the said resistor.
Would need half a house brick in size and I simply guess it won't work for your purpose.
Without any vital infos I also fail to see the point in this...

The laws of electrical nature will do it for you !

I surmise, you have a device rated 12vdc at 5A and you are concerned because the supply could deliver 16Amps and that can scare the non-EE beginner..

Do not worry, Because the device will only use the what current it needs and NOT the 16A that's what's available for other kinds_of_devices..