Ohm's Law and Voltage Divider
Calculate voltage, current, resistance, and power, and build a voltage divider, for example from 5 V to 3.3 V.
Ohm's Law states V = I × R: voltage (volts) is current (amperes) times resistance (ohms). Power is P = V × I. Fill in two values and the other two will be calculated. You can use a suffix: 20m is 0.02, 4.7k is 4700, and 1M is 1,000,000 (note: m is milli, M is mega).
A voltage divider uses two resistors to create a lower voltage: Vout = Vin × R2 ÷ (R1 + R2). Useful for stepping down a 5 V signal to 3.3 V for an ESP32 or Raspberry Pi, for example. Fill in the desired output voltage and R1, and you will get the value for R2.
A voltage divider is only suitable for signals with low current, such as a measurement input. The output will drop as soon as a load is applied. Use a voltage regulator or a level shifter for power supply or fast signals.