Electrical Calculators: Ohm's Law, Power and Resistors
Electrical calculators for hobbyists, students and electricians. Find a missing voltage, current or resistance, read the colour bands on a resistor or work out the resistor an LED needs.
For wiring work in a home, follow the current wiring regulations and use a qualified electrician where the law requires one.
Ohm's Law CalculatorEnter any two of voltage, current, resistance and power and get the other two.Voltage Divider CalculatorFind the output voltage of two resistors in series, with an optional load.Resistor Colour Code CalculatorRead the value of a 4, 5 or 6 band resistor, or find the colours for a value.Resistors in Series and Parallel CalculatorAdd resistors in series and parallel from a list of values such as 4.7k and 220.Capacitors in Series and Parallel CalculatorFind the total capacitance of capacitors in series and parallel from a list of values.LED Resistor CalculatorFind the series resistor for an LED from the supply, forward voltage and current.Voltage Drop Calculator (UK Cable)Estimate the voltage drop of a copper cable run and check it against the 3% and 5% limits.Battery Runtime CalculatorEstimate how long a battery will run a load, allowing for usable capacity and efficiency.RC Time Constant CalculatorFind the time constant, cut-off frequency and charging times for a resistor and capacitor.Wire Resistance CalculatorFind the resistance of a length of wire from its material, size and temperature.Decibel CalculatorConvert between decibels and power or voltage ratios, and between dBm and milliwatts.LC Resonant Frequency CalculatorFind the resonant frequency of an inductor and capacitor, with Q and bandwidth.Electrical Power CalculatorFind watts, volts or amps for direct current, single phase or three phase, with power factor and running cost.Inductive and Capacitive Reactance CalculatorFind the AC reactance of an inductor or a capacitor, and the impedance with a series resistor.Transformer CalculatorFind the turns ratio, secondary voltage, turns and currents of a transformer.
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