Electronics design calculators
electronics.tools is a small set of design calculators and learning notes for circuit work. Every tool runs in your browser. Nothing is stored, and there are no accounts.
Featured calculators
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Battery Life Calculator
Estimate run-time from battery capacity in mAh, average load current and an optional derating factor.
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Capacitor Calculator
Capacitive reactance Xc at a frequency and RC time constant τ from resistance and capacitance.
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LED Series Resistor Calculator
Size the series resistor for one LED string from supply voltage, forward voltage and current, then pick a nearby E-series value and check resistor power.
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Resistor Color Code Decoder
Decode 4-, 5- and 6-band through-hole resistor colour codes to resistance, tolerance and optional TCR.
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Ohm's Law Calculator
Solve V = I × R for voltage, current or resistance when you know the other two.
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Parallel Resistor Calculator
Combine resistors in parallel or series. See the equivalent resistance and the conductance of the network.
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Electrical Power Calculator
Compute DC power and the third quantity from any two of voltage, current and resistance using P = VI, I²R and V²/R.
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Reactance Calculator
Capacitive Xc and inductive Xl from frequency and capacitance or inductance.
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Electronics Unit Converter
Convert resistance, voltage, current, capacitance, inductance, frequency, time, power and energy with SI prefixes.
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Voltage Divider Calculator
Find the tap voltage of a two-resistor divider, see how a load pulls that tap down, and check the current and power in each resistor.