Electrical & Engineering Tools
Free online electrical calculators for voltage dividers, power, battery life, wire sizing, transformers, PCB traces, and more. Instant engineering results in your browser.
Voltage Divider Calculator
Calculate output voltage from two resistors in series — enter supply voltage and R1/R2 values for instant divider ratio and Vout.
Open tool →Power Calculator
Calculate electrical power in watts from voltage and current, voltage and resistance, or current and resistance — supports DC and AC with power factor.
Open tool →Battery Life Calculator
Estimate battery runtime from capacity in mAh and load current — add multiple loads to see combined drain hours and days.
Open tool →Capacitor Charge Time Calculator
Calculate RC charging time to any voltage level — enter resistance, capacitance, and supply voltage for time-to-percent milestones.
Open tool →Wire Size Calculator
Recommend AWG wire gauge from current, run length, voltage, and maximum voltage drop — includes mm² cross-section.
Open tool →Electricity Bill Calculator
Estimate daily, monthly, and yearly electricity cost from appliance wattage, usage hours, and your kWh rate.
Open tool →Transformer Calculator
Calculate transformer turns ratio and secondary voltage from primary voltage, secondary voltage, or known winding counts.
Open tool →Motor Power Calculator
Convert between motor torque, RPM, and shaft power in watts, kilowatts, and horsepower — bidirectional mechanical power math.
Open tool →PCB Trace Width Calculator
Estimate minimum PCB copper trace width from current, temperature rise, copper weight, and internal or external layer.
Open tool →Inductor Energy Calculator
Calculate energy stored in an inductor from inductance and current — essential for switching converters and flyback design.
Open tool →Series & Parallel Resistor Calculator
Calculate total resistance for resistors in series or parallel — enter multiple values for equivalent ohms instantly.
Open tool →RC Time Constant Calculator
Calculate RC time constant tau and charge milestone times — see 1τ through 5τ percentages for any resistor and capacitor pair.
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