Enter an Input Voltage and then the Output Voltage and finally the Current Draw (in AMPs) in the fields above then press CALCULATE to find other values. Hit RESET to clear the form, or SAMPLE if you want to see a sample calculation.

Voltage-Drop Resistor Calculator

Minimum Resistor Wattage

Required Dropping Resistor (Ohms)

Input Voltage

Output Voltage

Current Draw (AMPs)

Enter the following values to calculate the Dropping Resistor

Input Voltage - This is the Supply Voltage.

Output Voltage - This is the desired Output Voltage.

Current Draw - How much does this device draw in AMPs, it's OK to use decimals here so 25 milliamps is the same as 0.025 AMPs, 1/2 Amp would be 0.5 AMPs, etc.

Required Dropping Resistor - The Series Resistor in OHMS
Minimum Resistor Wattage - The Minimum Resistor Wattage, this is actually what the circuit draws so you should use a larger value to keep the Resistor from over heating.