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DC circuits & components calculators
Explore resistance, capacitance, energy and simple circuit relationships.
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Ideal component models omit tolerances, heat and parasitic effects. Distinguish nominal energy from usable energy for batteries. Component ratings and installation requirements need separate manufacturer and design checks.
Find a tool for your question
Ohms Law Current Calculator
Calculate ideal DC current from voltage and resistance.
Ohms Law Voltage Calculator
Find the voltage across an ideal resistor from current and resistance.
Ohms Law Resistance Calculator
Find ideal electrical resistance from voltage and current.
Electrical Power Calculator
Calculate DC electrical power from voltage and current.
Resistor Power Calculator
Calculate power dissipated as heat in a resistor.
Series Resistance Calculator
Add three resistors connected in series.
Parallel Resistance Calculator
Find equivalent resistance for two positive resistors in parallel.
Voltage Divider Calculator
Estimate unloaded output voltage from a two-resistor divider.
Battery Energy Calculator
Convert nominal battery voltage and amp-hours into nominal energy.
Battery Runtime Calculator
Estimate runtime from nominal battery energy, usable fraction and load power.
Ideal Battery Charge Time Calculator
Estimate the minimum constant-current time to replace a chosen capacity.
Capacitor Energy Calculator
Find stored energy in an ideal capacitor.
Series Capacitance Calculator
Find the equivalent capacitance of two ideal capacitors in series.
Parallel Capacitance Calculator
Add capacitances of two ideal parallel capacitors.
RC Time Constant Calculator
Calculate a resistor-capacitor circuit’s time constant.
RL Time Constant Calculator
Calculate the time constant of an ideal series resistor-inductor circuit.
LED Series Resistor Calculator
Estimate resistance for a single LED from source voltage, forward drop and current.
Transformer Voltage Calculator
Find ideal secondary voltage from primary voltage and turns ratio.
Voltage Drop DC Calculator
Estimate resistive voltage drop using current and total loop resistance.
Wire Resistance Calculator
Estimate conductor resistance from material resistivity, length and area.
Resistivity Calculator
Recover resistivity from a uniform sample’s resistance and dimensions.
Resistance Temperature Calculator
Estimate resistance change from a supplied linear temperature coefficient.
Current Density Calculator
Find average electrical current per conductor cross-sectional area.
Electric Charge Calculator
Find charge transferred during a current flow interval.
Current From Charge Calculator
Calculate average current from total transferred charge.
Capacitor Charge Calculator
Find electric charge stored on an ideal capacitor.
Capacitor Charging Voltage Calculator
Estimate voltage during ideal first-order RC charging.
Capacitor Discharge Voltage Calculator
Estimate capacitor voltage after an ideal RC discharge interval.
Inductor Energy Calculator
Find magnetic energy stored in an ideal inductor.
Inductor Voltage Calculator
Find ideal inductor voltage from the rate of current change.
Series Inductance Calculator
Add two uncoupled inductors connected in series.
Parallel Inductance Calculator
Find equivalent inductance for two uncoupled parallel inductors.
Parallel Plate Capacitance Calculator
Estimate ideal capacitance from plate geometry and dielectric permittivity.
Battery Series Voltage Calculator
Find the nominal voltage sum for identical battery units in series.
Battery Parallel Capacity Calculator
Find the nominal amp-hour sum of an ideal compatible parallel battery bank.
Battery C Rate Calculator
Express charge or discharge current relative to battery capacity.
Inverter Input Current Calculator
Estimate inverter DC current from output load and assumed efficiency.
DC Converter Efficiency Calculator
Compare measured DC converter output and input power.
Resistor Colour Value Calculator
Decode a conventional resistor’s two digits and multiplier into resistance.
Can these calculations select a safe installation rating?
No. They explain ideal relationships and do not include every thermal, protective or regulatory requirement.
Useful next steps in other categories
Appliance Energy Calculator
Estimate electricity consumption from appliance power and operating hours.
Electricity Cost Calculator
Calculate energy charges from consumption and a manually entered unit rate.