Question

Using r.i.v.p. How do I calculate circuits wit 12 volts

Answer 1

You don't calculate a circuit.  You calculate the voltage, current, capacitance,
resistance, inductance, impedance, phase, power factor, frequency response,
or reflection coefficient of the circuit, and other stuff like that there.

Tell us what you need to find, and what information you have, and we'll
show you how to use what you have to find what you need to find.