Voltage divider is actually two resistors connected in series.
Now, if we know VCC and R1 and R2 resistor value, there is a question, how much is VOUT? By intuition, if R1=R2 then VOUT is one half of VCC. But we need to calculate this output voltage exactly. First step is to find current through R1 and R2 by using Ohm’s law.
Knowing current, we can calculate output voltage as voltage drop on resistor R1:
So voltage divider formula is
Voltage divider is just two resistor connected is series, but powerful tool for calculating electrical potential of some nodes. Instead of solving system of equations, all we need to do in order to calculate output voltage of an voltage divider is to find quotient of resistor value and sum of two resistors that makes voltage divider, and then to find product of this quotient and input voltage. Voltage divider is widely used in electronics for transistor biasing as well in different kind of electric measurement.
Go to voltage divider online calculator.