Question about current

I kinda don't understand the whole drawing current thing, I know I'm going to need a multimeter and I understand that current is how much power is being drawn from a power source (and to much can damage a IC or micro controller). My question is how can I figure out how much current all the component I'm using will draw in (like a Ping range finder, and a L923NE and the two motors use their own power source). Like would I have to find the data out (through data sheets and the multimeter) and add it up together (i.e. Ping_range_finder_A+L923NEA)?

My question is how can I figure out how much current all the component I'm using will draw in (like a Ping range finder, and a L923NE and the two motors use their own power source). Like would I have to find the data out (through data sheets and the multimeter) and add it up together (i.e. Ping_range_finder_A+L923NEA)?

Basically it is from two sources, datasheets and actual measurements. Some things are hard to pin down, like motors. Motors will draw different amount of current depending on the actual mechanical load, with worst case being if one holds the rotor fixed, locked rotor current. And yes finally adding all the load currents is required to get a overall current draw value.

Also current is not power. Power is voltage X current. Current is voltage divided by load resistance. A basic understanding of ohms law is what can help one learn the required theory.

Yeah I understand the ohm law thing, I missed typed what I was asking, but thanks you explained what i wanted to know.