https://www.altestore.com/howto/wire-sizing-tool-for-12-24-and-48-volt-dc-systems-a106/
This is easy place to go if you don’t have set electrical charts. If in doubt go heavier it can’t hurt you other than pocket book, being cheap can cost you everything. DON’T GO TO LOCAL ELECTRICAL PLACE AND EXPECT THEM TO KNOW ANYTHING ABOUT DC.
I for quick calculation on amp it’s the watts drawn divided by the supply voltage. So a 120v (standard house plug) powering a 250 watt bulb is 250/120 is 2.083 amps. This does not include for voltage spikes at start. Rule of thumb is if the breaker for ac says 15 amp max you should put on circuit if it all comes on at once is 10-11 amps the rest is used for the surge draw. Any more and you can cause an electrial fire. Check local code for construction as some places have different regulations on this.
Ac wire guide
https://www.homedepot.com/c/factors_to_consider_when_wiring_your_home_HT_BG_EL