We have added a pie chart showing the efficiency of the circuit, the red zone indicates the energy consumption in the resistor, the green zone shows the energy consumed in the led. Really calculate the resistance for your leds in series or parallel, just enter in the fields the source voltage values, the number of leds, led voltage, the led current, touch calculate and you will be able to see the result immediately, If you want to see additional information, touch the + button, then you will see