Electrical Calculators

Professional electrical engineering tools for cable sizing, load calculations, transformer sizing, and system design per NEC/IEC standards.

Most used in Electrical

Cable Size CalculatorCable size in mm² or AWG by current, derating and voltage drop (IEC, BS 7671 & NEC)Load Current CalculatorCalculate load current from power and voltagePower Factor CalculatorCalculate PF, kVA, kVAR & phase angle from kW, voltage and current — single & three phase with calculation steps

All 31 Electrical calculators

Cable Size CalculatorCable size in mm² or AWG by current, derating and voltage drop (IEC, BS 7671 & NEC)Electrical Panel Load CalculatorBuild a panel schedule with demand load, auto cable size (Cu/Al), voltage drop, derating & breaker sizing (IEC & NEC)Load Current CalculatorCalculate load current from power and voltageMotor Starter SizingDOL and star-delta contactors, overload setting and motor FLC tableBusbar SizeCopper or aluminium phase, neutral and earth busbar sizesSolar PV System SizeSolar array kWp, number of panels, battery and inverter sizeBattery Backup Time CalculatorBackup hours from battery Ah and load, or batteries needed, with Peukert correctionEV Charger Load CalculatorMain breaker, branch breakers and transformer for AC and DC EV chargers (NEC 625 / IEC 60364-7-722)ESE Lightning Arrester CalculatorESE protection radius to NFC 17-102, roof coverage and number of arrestersNeutral Current CalculatorNeutral current from unbalanced phases and 3rd harmonics, with IEC cable sizingResidential LoadCalculate residential electrical load per NECTransformer SizingSize transformers based on connected loadTransformer Sizing (Pro)Advanced transformer sizing with loading margin, ambient derating & ANSI/IEC ratingsCable Tray Fill CalculatorMinimum tray width per NEC 392.22 or percent fill (IEC practice)Conduit Fill CalculatorMinimum conduit size and % fill for EMT, IMC, RMC & PVC per NEC Chapter 9Voltage DropCalculate voltage drop in electrical cablesShort CircuitCalculate fault current for equipment ratingLighting LuxCalculate lighting levels and fixture requirementsGenerator SizingSize standby generators for buildingsGenerator Fuel & Day TankDiesel L/h at any load, day tank and main storage sizePower Factor CalculatorCalculate PF, kVA, kVAR & phase angle from kW, voltage and current — single & three phase with calculation stepsPower Factor CorrectionCapacitor bank kVAR to raise power factor, with kVA and current before and afterEarthing/GroundingDesign earthing systems per IEEE 80kW CalculatorFull kW power calculator for single-phase & three-phase systemskW to AmpsConvert kW to current (amps) for 1φ and 3φ systemskW to Cable SizeQuick cable size recommendation from kW, voltage, PF, and lengthkW to BTU/hrConvert kW to BTU/hr for HVAC heat load calculationskW to HPConvert kW to horsepower (HP) with selectable HP type & efficiencykW to kVAConvert kW to kVA and kVAR using power factor (PF) with steps & analysisBreaker Size CalculatorSelect standard breaker rating from amps or kW with optional IEC/NEC verificationCapacitor Color Code CalculatorDecode capacitor color bands & printed codes (104, 473, 4R7) to pF/nF/µF with tolerance — plus reverse value-to-code mode

Free Electrical Engineering Calculators

These calculators cover the everyday design checks on an electrical project, from the first load estimate to cable, breaker and transformer selection. Each tool shows its formula and calculation steps, so you can check the result instead of trusting a black box, and states the standard it follows: IEC 60364, BS 7671 or the NEC.

Cable and Conductor Sizing

The Cable Size Calculator sizes copper or aluminium cable in mm² or AWG from current-carrying capacity, temperature and grouping derating, and voltage drop. Start from kW with the kW to Cable Size Calculator, check long runs with the Voltage Drop Calculator, and size the protective device with the Breaker Size Calculator.

Power, Load and Power Factor

Convert between kW, kVA, amps and horsepower, build a panel schedule with the Electrical Panel Load Calculator, and find power factor, kVA and kVAR with the Power Factor Calculator. To improve a low power factor, the Power Factor Correction Calculator sizes the capacitor bank.

Power System Design

Size transformers and standby generators, estimate short circuit current for equipment ratings, design earthing systems, and plan lighting levels in lux. Results are design estimates; final designs should be verified against the applicable code and manufacturer data.

Other disciplines

HVACFire FightingPlumbingBMS & ELVUtility