formula to work out pcb trace size?
hi. i am going to be making pcb's for some of my projects wich will include different voltages, amps etc. i am new to pcb making (although i have designed some in the past) and want to know what size i need to make my traces so that they are safe, for example: a 9v 500ma circuit will use smaller traces than a 240v 13a circuit. i was just wondering if there was a formula or website for working this out?
thanks in advance - luke