Review Ohm's law. The law expresses the relationship among current, voltage and resistance. The algebraic symbols used are E for voltage, which is measured in volts; I for current, which is measured in amperage (amps); and R for resistance, which is measured in Ohms. The formula for finding current is I = E/R, or Current = Voltage/Resistance.
Set the voltage range on a multimeter meter to a value in line with the voltage supplied to the circuit. In an automotive circuit, for example, the voltage is no more than 14.7 volts. So you would set the meter's voltage range to 20 volts. A digital multimeter maxes out its range by displaying a 1. If you see a 1, select the next higher range.
Measure the voltage dropped across each resistor by placing a multimeter lead on each leg of the resistor.
Record the voltage values for later calculations. If the voltages are not the same value, then the resistors are not in parallel with each other.
Decode the value of the resistors in the circuit using the resistor color code. For a typical five-band resistor, these numbers are associated with each value: black equals 0, brown is 1, red is 2, orange equals 3, yellow is 4, green is 5, blue equals 6, violet is 7, gray equals 8 and white is 9.
Find the tolerance band, which is silver or gold. Starting from the end of the resistor opposite the tolerance band, write down the corresponding values of the first two colors in order. If the colors are brown and black, for example, then the corresponding numbers are 1 and 0, respectively.
For the resistor's third band, write a corresponding number of zeroes after the numbers you just wrote down. If the third color band is red, for instance, then you write two zeroes after the "10" you just recorded to get "1000." That number is the value of the resistor in Ohms.
Place the numbers in the appropriate spots in the calculation. You will have one value for voltage and two values for resistance. If voltage is 5 volts and the resistor values are 1000 ohms and 100 ohms, for example, then the calculation is set up like this: I = 5/1000 and I = 5/100.
Solving for "I," the result is .005 amps of current for the first resistor and .05 amps of current through the second resistor.