Voltage Divider Calculator
Compute output voltage and resistor power dissipation. Features a reverse calculator to find resistor pairs (E12-E96) for a target voltage.
About
A voltage divider is one of the most fundamental circuits in electronics, used to scale down high voltages for microcontrollers or to set reference levels. However, a common engineering oversight is neglecting the output impedance and power dissipation. If the resistors are too small, they will overheat and burn; if they are too large, the output voltage becomes unstable when a load is attached.
This tool calculates the output voltage based on input source and resistor values. Uniquely, it also monitors the wattage across each component, flagging unsafe conditions where a standard 14 W resistor would fail. It supports reverse calculation to find the best standard resistor combination for a specific target voltage.
Formulas
The unloaded output voltage is determined by the ratio of the resistors.
Divider Equation:
Vout = Vin × R2R1 + R2Power dissipated by each resistor must be checked against component ratings.
Power R1:
PR1 = (Vin − Vout)2R1Power R2:
PR2 = Vout2R2Reference Data
| Series | Values per Decade | Tolerance | Common Applications |
|---|---|---|---|
| E6 | 6 | 20% | Audio speakers, coarse pull-ups |
| E12 | 12 | 10% | General purpose, consumer electronics |
| E24 | 24 | 5% | Timing circuits, regulators, filtering |
| E48 | 48 | 2% | Precision Analog, ADC inputs |
| E96 | 96 | 1% | High-precision measurement, medical |
| E192 | 192 | 0.5-0.1% | Aerospace, calibration equipment |