Things You'll Need
Instructions
DC Voltage and Current
Key the DC voltage value into the calculator. For example, if the circuit voltage is 4 volts, key in "4."
Press the "Multiply" key. Enter the DC current into the calculator. For this example, your circuit has 2 amps of current, so enter "2."
Press the "Equals" key. The result is DC watts. In this example, 4 volts x 2 amps = 8 watts.
DC Current and Resistance
Enter the current measurement into the calculator. Multiply the number by itself to square it. For example, if your circuit has 2 amps of current, multiply 2 times 2 to get 4.
Press the "Multiply" key. Enter the DC resistance in ohms. In this example, your circuit has a resistance of 2 ohms. Enter "2" into the calculator.
Press the "Equals" key. The result is DC power in watts. For this example, 4 x 2 = 8 W.
DC Volts and Resistance
Enter the DC voltage into the calculator. Multiply the number by itself to square it. For example, if your circuit has 4 volts, multiply 4 times 4 to get 16.
Press the "Divide" key. Enter the resistance of the circuit in ohms. In this example, your circuit has a resistance of 2 ohms. Enter "2" into the calculator.
Press the "Equals" key. The result is DC watts. For the example, 16 / 2 = 8 W.
AC Volts and Amps
Key in the AC voltage value into the calculator. For this example, the voltage is 110 volts RMS, so enter "110."
Press the "Multiply" key. Enter the AC current. For this example, your AC current is 2 amps. Enter "2." If the voltage is an RMS value, as in this example, skip Step 3 and proceed to Step 4.
Press the "Multiply" key. Enter the value ".707." Remember to do this only if the voltage value is peak voltage. Otherwise, skip this step.
Press the "Equals" key. The result is AC watts. In our example, using an RMS voltage value of 2 volts, 110 x 2 = 220 W.