Hi,

That all depends on the amperage draw on the items under the dash or going elsewhere.

Each circuit get a size wire that carries its own rating.

No. 14 gage is the center, for remembering a rule of thumb (for me) and it equals 15 amps.
The numerals are the closest together.
From there you go up or down 5 amps with each size.
The smaller the number gage, the more amperage or current It carries.
The larger the number gage, the less amperage or current It carries

A 12 gage carries 20 amps.
A 14 gage carries 15 amps.
A 16 gage carries 10 amps.
A 18 gage carries 5 amps.

Above and below this band of sizes, the amperages change more dramatically so, refer to a wiring chart.
An example is a 10 gage can carry 30 amps.

Fuses are sized for the wire size that they are to put in to protect and that’s it!
You don’t put in smaller wire with a larger fuse or the protection is defeated!

Phil