The calculators on this page can be used to find current limiting resistors and currents for Light Emitting Diodes.
The first calculator determines the resistance for a desired LED current while the second calculates the current for a given resistance.
LED - Current and Resistance Calculator Diagram
LED - CURRENT LIMITING RESISTOR CALCULATOR
Voltages in Volts - Current in Milliamps - Resistance in Ohms
When selecting resistors - It is advisable to choose the next higher standard value.
LEDs should always be connected in series or series-parallel for longer or larger arrays/clusters. We normally build them with 3 LEDs and one resistor that is sized to match the supply voltage or power source. For larger or longer clusters/arrays, connect one series to another in parallel. To determine the "Voltage Drop", multiply the LED's "Forward Voltage" as shown on the LED's data sheet by the number of LEDs to be installed.
Entering a zero for the LED voltage drop will yield the resistance and wattage for a resistance only circuit.