Enter any two values — the third fills in automatically
V = I × R) and power is P = V × I. Series resistance is the sum; parallel is the reciprocal of the summed reciprocals. A voltage divider is Vout = Vin × R2 / (R1 + R2). The colour-code decoder maps band colours to the standard digit/multiplier/tolerance tables.
Add up to 8 resistors to find the combined resistance
Vout = Vin × (R2 / (R1 + R2))
4-band resistor: 2 digits, a multiplier, and a tolerance
Ohm's Law fills in whichever of voltage, current, or resistance you haven't entered, using the other two: V = I × R, rearranged as needed depending on which value is missing.
Power is calculated as P = V × I. For resistor networks, resistors in series simply add together, while resistors in parallel combine as the reciprocal of the sum of reciprocals — the standard circuit analysis formulas taught in any introductory electronics course.
A voltage divider calculates output voltage as Vout = Vin × R2 / (R1 + R2), a common building block in electronic circuits. The resistor colour-code decoder maps the coloured bands on a physical resistor to the standard digit, multiplier, and tolerance tables used to read a resistor's value without needing a multimeter.
It fills in whichever of voltage, current, or resistance you leave blank, using the two values you do provide and rearranging V = I × R accordingly.
In series, resistances simply add together. In parallel, you take the reciprocal of the sum of the reciprocals of each resistance — a smaller total than the smallest individual resistor in the group.
It calculates the output voltage across one resistor (R2) in a two-resistor series circuit fed by an input voltage, using Vout = Vin × R2 / (R1 + R2) — a common way to create a reduced reference voltage in a circuit.
It maps the sequence of coloured bands on a physical resistor to standard digit, multiplier, and tolerance values using the internationally recognized resistor colour-code system, letting you read a resistor's value without a multimeter.