Voltage Drop Calculator
Volts lost, percentage drop and voltage at the load for DC, single-phase and three-phase runs, in copper or aluminium, against the 3% / 5% guidance.
Free Electrical Tools & Calculators
Every tool below runs instantly in your browser — no sign-up, no downloads, nothing uploaded anywhere. They cover the calculations electricians, engineers and students search for most: sizing conductors, checking voltage drop, solving Ohm's law, sizing motors and LEDs, and pricing energy use. Results are for estimation and checking; always verify against the equipment nameplate, the applicable code, and project documentation.
Field & installation tools
Wire Size Calculator
The smallest AWG conductor that passes both ampacity and your voltage drop limit — the two tests every conductor selection must satisfy.
Ohm's Law Calculator
Enter any two of voltage, current, resistance and power; get the other two instantly, with the formulas shown.
Three-Phase Power Calculator
kW, kVA, kVAR and line current from voltage, current and power factor — for motors, transformers and mixed loads.
Motor FLA Calculator
Full-load amps from horsepower, voltage, phase, efficiency and power factor, plus the 125% conductor ampacity for sizing.
Electricity Cost Calculator
Daily, monthly and yearly kWh and cost from watts, hours per day and your tariff — for appliances, workshops and plant.
Electronics tools
Resistor Color Code Calculator
Decode 4, 5 and 6-band resistors: resistance, tolerance and temperature coefficient from the band colours.
LED Resistor Calculator
Series resistor value, nearest standard E24 value and safe wattage from supply voltage, LED forward voltage and current.
Transformer Calculators
The original LOTICI set: three-phase kVA ↔ amps, transformer load percentage, and turns ratio / secondary voltage.
Installation & power tools
Conduit Fill Calculator
NEC Chapter 9 fill percentage for EMT conduit with THHN conductors, with the 53% / 31% / 40% limits.
Breaker & Fuse Size Calculator
Next standard breaker or fuse size (NEC 240.6) from load current, with the 125% continuous-load rule.
Power Factor Correction Calculator
Capacitor kVAR needed to lift power factor to your target, and the freed kVA capacity.
Battery Runtime Calculator
Backup hours from battery Ah, voltage, load, depth of discharge and inverter efficiency.
Solar PV Sizing Calculator
Array size in kW and panel count from daily energy use, peak sun hours and system losses.
AWG to mm² Converter
Cross-section area and diameter for every common AWG size, convertible both ways.
Voltage Divider Calculator
Output voltage from two resistors, or the resistor value for a target output voltage.
Series & Parallel Resistor Calculator
Equivalent resistance for up to six resistors, in series and in parallel, instantly.
Want the theory behind the numbers? Read the full guide library, starting with the transformer testing and commissioning guide.