Voltage Divider Calculator
Calculate the exact output voltage ($V_{out}$) and total current in a simple resistor voltage divider circuit.
Circuit Setup
Resistors
R1
Ω
R2
Ω
Output Voltage (V_out)
0 V
Idle Current (I)
0 A
How a Voltage Divider Works
A voltage divider is one of the most fundamental circuits in electronics. It allows you to take a large voltage and "step it down" to a smaller voltage using just two resistors.
- The Formula:
V_out = V_in × (R2 / (R1 + R2)) - The Ratio: The output voltage is entirely determined by the ratio of the two resistors. If $R_1$ and $R_2$ are exactly the same value (e.g., 100Ω and 100Ω), the output voltage will always be exactly half (50%) of the input voltage.
- Current (Idle Load): Even if nothing is connected to $V_{out}$, electricity constantly flows from $V_{in}$ through $R_1$ and $R_2$ to Ground. This "idle current" wastes power as heat. Higher resistor values waste less power, but lower resistor values provide a "stiffer" (more stable) output signal.
Warning: Never use a voltage divider as a power supply!
Voltage dividers are only designed to provide low-current reference signals (like telling a microcontroller or Arduino what a voltage is). If you try to power a load (like a motor or a lightbulb) from the $V_{out}$ pin, the load itself acts like a third resistor connected in parallel with $R_2$. This immediately destroys the math ratio, causing the voltage to drop drastically! To drop voltage for power supplies, use a voltage regulator or a buck converter instead.
Voltage dividers are only designed to provide low-current reference signals (like telling a microcontroller or Arduino what a voltage is). If you try to power a load (like a motor or a lightbulb) from the $V_{out}$ pin, the load itself acts like a third resistor connected in parallel with $R_2$. This immediately destroys the math ratio, causing the voltage to drop drastically! To drop voltage for power supplies, use a voltage regulator or a buck converter instead.