Learn
These guides explain the ideas behind the calculators: resistor standards, divider math, LED current, capacitor families, and more. Each page links to tools and related categories.
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Battery capacity and runtime
Convert mAh to runtime with load current and efficiency factors.
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Capacitive and inductive reactance
Xc and Xl at a frequency with links to the reactance calculator.
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Capacitor types for bypass and bulk
Ceramic, electrolytic, and film capacitors — where each belongs in a board.
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Common SMD package sizes
Footprint codes for resistors, capacitors, and small ICs — facts only, no substitution guarantees.
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E-series resistor values (E12, E24, E96)
How IEC 60063 preferred value series work and when to pick E12 versus E24 or E96.
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LED current-limiting resistors
Pick a series resistor from supply voltage, LED forward voltage, and target current.
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Ohm's law for circuit checks
The relationship V = I × R with unit tips and links to the Ohm's law calculator.
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Resistor color code
Read four- and five-band resistor color codes and check values with the decoder tool.
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Series and parallel resistors
Combine resistors to hit a value or share power.
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Voltage dividers
Scale DC voltages with two resistors and avoid loading errors.