To carry 5 Amps with a 20°C temperature rise on an external layer, the PDF shows you need approximately 50 mils of 2 oz copper (or 100 mils of 1 oz copper). For internal layers, you must derate by 50% (use 100 mils of 2 oz copper).
: IPC-2221 gives generic rules; IPC-2222 and IPC-2223 provide technology-specific additions.
IPC-2221 provides the "generic" rules that apply to all PCB types, including single-sided, multilayer, and rigid-flex designs. IPC-2221 Standards in PCB Design - Sierra Circuits
In the , you will find logarithmic charts showing: