Does anybody know what gauge the power wire is from the fuse box to the battery on a 99 honda civic Lx?

 

4 AWG should suffice. Honestly, the factory wire looks more like 6 AWG....

 

I forgot to upgarde this as well. Its 8awg. 4awg doesn't fit in there I already tried unless you start breaking some of the plastic of the fuse box. The screw that screws both wires in is 1/4 ring hole. I tried a 5/16 4awg ring terminal and it doesnt fit. 1/4 8awg ring terminal fits perfectly.