A voltage divider lets you convert an input voltage to a lower output voltage. For example a 5V input can be converted to a 3V3 output quite easily. The basic setup is made of two resistors:
But choosing the right resistors is quite tricky. You could take the formula and try some values in order to approximate the values or use the calculator formula:
|Desired Output Voltage||V|
Please note: Don't use a voltage divider for high voltages, as the entire current has to pass the resistors, which will hurt them a lot. Alternatives are voltage regulators! And even more important: You shouldn't use low value resistors in real world voltage dividers. The power disipation column states how much energy is converted into heat and should be as low as possible.