Lightning exposure, SPD selection, coordination, and backup protection
SPD Calculator
Choose a starting surge protective device type for AC, DC, or PV systems based on exposure, installation point, and system earthing.
Open calculatorVIOX engineering tools
Low-voltage calculation tools for practical product selection.
Support panel builders, OEMs, distributors, and electrical engineers with quick reference checks for surge protection, circuit protection, cable sizing, motor control, and EV charging loads.
Guided workflowSize a circuit in four steps
Move from connected load to a checked conductor.
- 01Calculate Load CurrentPower → operating currentIb→
- 02Select Breaker RatingCurrent → MCB or MCCBIn→
- 03Size the ConductorCurrent + installationIz→
- 04Check Voltage DropCable + route lengthVd%→
Protection relationshipIb ≤ In ≤ Iz→Check Vd%
84Electrical
calculators
calculators
Conductor size, ampacity, voltage drop, and fault withstand
Voltage Drop Calculator
Estimate voltage drop by current, conductor length, material, cross-section, and phase system.
Open calculatorConductor size, ampacity, voltage drop, and fault withstand
Cable Size Calculator
Find a reference conductor size from load current, sizing factor, conductor material, and installation severity.
Open calculatorConduit, tray, glands, lugs, routing, and cable entry
Conduit Fill Calculator
Calculate conduit fill percentage from pathway type, trade size, cable outside diameter, and cable quantity.
Open calculatorConductor size, ampacity, voltage drop, and fault withstand
DC Voltage Drop Calculator
Check DC voltage drop for 12 V, 24 V, 48 V, control, LED, battery, and PV accessory circuits using AWG conductor resistance.
Open calculatorConductor size, ampacity, voltage drop, and fault withstand
AWG Wire Size Calculator
Find the smallest AWG conductor that passes both reference ampacity and voltage-drop checks.
Open calculatorConductor size, ampacity, voltage drop, and fault withstand
mm² to AWG & AWG to mm² Converter
Convert conductor cross-sectional area between metric mm² and American Wire Gauge, with nearest and not-smaller standard-size references.
Open calculatorBreakers, fuses, fault current, grounding, and arc flash
Circuit Breaker Size Calculator
Estimate a standard MCB or MCCB current rating from load power, voltage, phase, power factor, and sizing factor.
Open calculatorTransformers, demand, ATS, busbars, power quality, and generators
Transformer Sizing Calculator
Estimate transformer kVA from connected load, demand factor, future growth, loading margin, ambient derating, and standard rating series.
Open calculatorBreakers, fuses, fault current, grounding, and arc flash
Short Circuit Current Calculator
Estimate available transformer secondary fault current from transformer kVA, impedance, voltage, phase, and optional utility fault contribution.
Open calculatorCore formulas, phase power, resistance, circuits, and units
kW, kVA and Amp Calculator
Choose kVA to amps, amps to kW, or kW to amps and see only the inputs required for that calculation.
Open calculatorCore formulas, phase power, resistance, circuits, and units
Three Phase Current Calculator
Calculate three-phase current from kW or kVA, line voltage, power factor, and efficiency.
Open calculatorMotor current, starting, contactors, voltage quality, and VFDs
Motor Current Calculator
Estimate motor full-load current and a starting overload relay setting range from motor power, voltage, efficiency, and power factor.
Open calculatorCharging time, cost, current, demand, and feeder planning
EV Charger Load Calculator
Estimate EV charger current and total distribution load from charger power, phase, quantity, and simultaneity.
Open calculatorConduit, tray, glands, lugs, routing, and cable entry
Cable Gland Size Calculator
Select a cable gland by cable outside diameter or check Metric, PG, NPT, and G/BSPP entry threads.
Open calculatorTransformers, demand, ATS, busbars, power quality, and generators
Busbar Current Rating Calculator
Estimate busbar current from width, thickness, material, current-density reference, and derating factor.
Open calculatorBreakers, fuses, fault current, grounding, and arc flash
Fuse Sizing & Selection Calculator
Size a preliminary gG, aM, or gPV fuse and check load current, cable ampacity, breaking capacity, motor starting duty, or PV module limits.
Open calculatorCore formulas, phase power, resistance, circuits, and units
Power Factor Calculator and Correction
Analyze active, reactive, and apparent power or calculate the capacitor-bank kvar needed to improve power factor.
Open calculatorMotor current, starting, contactors, voltage quality, and VFDs
Motor Starter Selection Calculator
Estimate motor current, starting current, contactor duty, overload-relay range, and preliminary short-circuit protection for a motor starter.
Open calculatorMotor current, starting, contactors, voltage quality, and VFDs
Three-Phase Voltage Unbalance Calculator
Calculate three-phase voltage unbalance, voltage-window thresholds, and select a starting VIOX FCP18 monitoring-relay function.
Open calculatorPV strings, batteries, inverters, UPS, charging, and backup energy
PV Combiner Box Sizing Calculator
Size key PV combiner-box ratings from module Voc, Isc, temperature coefficient, series modules, parallel strings, cable ampacity, and lightning exposure.
Open calculatorLightning exposure, SPD selection, coordination, and backup protection
Advanced SPD Selection Calculator
Select a preliminary SPD type, connection arrangement, Uc or Ucpv range, discharge-duty level, and backup-protection checks.
Open calculatorBreakers, fuses, fault current, grounding, and arc flash
MCB Inrush Compatibility Checker
Compare equipment inrush current with IEC-style B, C, or D magnetic-trip bands and check whether available fault current supports instantaneous operation.
Open calculatorBreakers, fuses, fault current, grounding, and arc flash
RCD & RCBO Selection Calculator
Select a starting residual-current type, sensitivity, poles, rated current, overcurrent curve, and breaking capacity for common loads.
Open calculatorTransformers, demand, ATS, busbars, power quality, and generators
ATS Selection Calculator
Select a preliminary ATS current rating, PC or CB class, pole arrangement, transfer-speed category, and UPS or STS requirement.
Open calculatorConduit, tray, glands, lugs, routing, and cable entry
Cable Lug Selection Calculator
Select a preliminary cable-lug material, conductor marking, stud hole, palm style, finish, and connection method.
Open calculatorPV strings, batteries, inverters, UPS, charging, and backup energy
Battery C-Rate & Runtime Calculator
Calculate battery C-rate, P-rate, nominal and usable energy, discharge current, and estimated runtime for packs or BESS projects.
Open calculatorPV strings, batteries, inverters, UPS, charging, and backup energy
Electrical Energy Cost Calculator
Calculate daily, monthly, and annual electricity consumption and operating cost from power, runtime, quantity, load factor, and tariff.
Open calculatorPanel heat, terminals, clearances, creepage, and enclosure ratings
Electrical Terminal Heating Calculator
Calculate contact power loss, voltage drop, daily heat energy, and optional temperature-rise estimate from current and contact resistance.
Open calculatorTransformers, demand, ATS, busbars, power quality, and generators
Busbar Short-Circuit Force Calculator
Estimate electrodynamic force between parallel busbars from peak short-circuit current, conductor spacing, and unsupported support span.
Open calculatorCore formulas, phase power, resistance, circuits, and units
RC Circuit and Time Constant Calculator
Calculate RC time constant, cutoff frequency, charging and discharging voltage, capacitive reactance, impedance, gain, and phase at one frequency.
Open calculatorCore formulas, phase power, resistance, circuits, and units
RLC Impedance and Resonance Calculator
Calculate series or parallel RLC reactance, impedance, admittance, current, phase angle, power factor, resonance frequency, and Q factor.
Open calculatorCore formulas, phase power, resistance, circuits, and units
Current Divider Calculator
Split a known total current across two to six parallel resistive branches and calculate equivalent resistance, common voltage, branch current, and branch power.
Open calculatorCore formulas, phase power, resistance, circuits, and units
Capacitor Reactance and Energy Calculator
Calculate capacitive reactance, RMS current, stored energy, charge, peak current screen, and series or parallel equivalent capacitance.
Open calculatorCore formulas, phase power, resistance, circuits, and units
Inductor Reactance and Energy Calculator
Calculate inductive reactance, RMS current, stored magnetic energy, time constant, and series or parallel equivalent inductance.
Open calculatorCore formulas, phase power, resistance, circuits, and units
Current Shunt Calculator
Size or verify a DC current shunt from rated current and millivolt drop, including resistance, power loss, burden voltage, and meter scaling.
Open calculatorLux, lumens, fixtures, circuits, efficiency, and emergency lighting
Emergency Lighting Battery Calculator
Estimate emergency-lighting battery Wh and Ah from fixture load, duration, efficiency, depth of discharge, aging, temperature, and design margin.
Open calculatorLux, lumens, fixtures, circuits, efficiency, and emergency lighting
Lighting Circuit Load Calculator
Calculate connected lighting watts, input VA, current, energy, circuit quantity, loading per circuit, and LED driver inrush screening.
Open calculatorTransformers, demand, ATS, busbars, power quality, and generators
Branch Circuit Count Calculator
Estimate branch-circuit quantity from floor area, general load density, circuit voltage and rating, planned loading, dedicated circuits, and optional NEC dwelling circuits.
Open calculatorTransformers, demand, ATS, busbars, power quality, and generators
Electrical Panel Load and Spare Capacity Calculator
Calculate panel kVA, current, utilization, spare amperes, spare kVA, phase-load unbalance, and expansion impact from entered demand loads.
Open calculatorTransformers, demand, ATS, busbars, power quality, and generators
Transformer Impedance Calculator
Calculate transformer full-load current, ohmic impedance, R and X components, X/R ratio, and infinite-bus secondary fault current.
Open calculatorTransformers, demand, ATS, busbars, power quality, and generators
Generator Sizing Calculator
Estimate generator kW and kVA from running load, largest starting step, power factor, reserve, growth, altitude, and ambient derating.
Open calculatorTransformers, demand, ATS, busbars, power quality, and generators
Harmonic and THD Calculator
Calculate THD, total RMS, individual harmonic distortion, triplen content, crest-factor screen, and neutral-current warning from harmonic magnitudes.
Open calculatorPV strings, batteries, inverters, UPS, charging, and backup energy
UPS Backup Time Calculator
Estimate UPS battery runtime from load, battery voltage and Ah, series and parallel configuration, inverter efficiency, aging, and depth of discharge.
Open calculatorPV strings, batteries, inverters, UPS, charging, and backup energy
Inverter Sizing Calculator
Estimate inverter continuous kW, kVA, surge rating, DC input current, AC output current, and PV DC array reference from load and design margins.
Open calculatorBreakers, fuses, fault current, grounding, and arc flash
Grounding Resistance Calculator
Estimate single vertical ground-rod resistance and a preliminary multiple-rod result from soil resistivity, rod length, diameter, count, and spacing.
Open calculatorMotor current, starting, contactors, voltage quality, and VFDs
Insulation Resistance Temperature Correction Calculator
Correct a measured insulation-resistance value to a reference temperature using a selectable doubling-temperature or entered correction coefficient.
Open calculatorConduit, tray, glands, lugs, routing, and cable entry
Cable Pulling Tension Calculator
Estimate straight-section pulling tension, capstan tension after a bend, sidewall pressure, and allowable-tension utilization for a simplified cable pull.
Open calculatorMotor current, starting, contactors, voltage quality, and VFDs
Motor Torque Calculator
Calculate motor shaft torque, output power, input power, angular speed, and lb-ft from kW or hp, rotational speed, and efficiency.
Open calculatorMotor current, starting, contactors, voltage quality, and VFDs
Motor Control Panel Load Calculator
Estimate an MCC or motor-control-panel feeder ampacity from the largest motor, remaining motors, non-motor load, demand, and spare capacity.
Open calculatorCore formulas, phase power, resistance, circuits, and units
Three-Phase Power Calculator
Calculate balanced three-phase active power, apparent power, reactive power, current, phase angle, and power-factor improvement effects.
Open calculatorPV strings, batteries, inverters, UPS, charging, and backup energy
Battery Capacity Converter
Convert battery Ah, mAh, Wh, and kWh while accounting for voltage, series and parallel configuration, depth of discharge, and efficiency.
Open calculatorCore formulas, phase power, resistance, circuits, and units
Power, Energy & Time Calculator
Enter any two of power, energy, and operating time to calculate the third with automatic electrical-unit conversion.
Open calculatorCore formulas, phase power, resistance, circuits, and units
Voltage Divider Calculator with Load
Calculate a two-resistor voltage divider, solve for either resistor, or include load resistance to quantify output error and resistor power.
Open calculatorPanel heat, terminals, clearances, creepage, and enclosure ratings
Clearance & Creepage Calculator
Estimate IEC 60664-1 minimum clearance through air and creepage along an insulating surface from voltage, overvoltage category, pollution degree, CTI group, insulation level, and altitude.
Open calculatorCore formulas, phase power, resistance, circuits, and units
PCB Conductor Spacing Calculator
Estimate a PCB conductor-spacing reference from voltage and conductor environment, or calculate the maximum reference voltage for an available spacing.
Open calculatorCore formulas, phase power, resistance, circuits, and units
Ohm's Law Calculator
Enter any two of voltage, current, resistance, and power to calculate the other two electrical quantities.
Open calculatorCore formulas, phase power, resistance, circuits, and units
Watts to Amps and Volts Calculator
Convert watts, amps, and volts for DC, single-phase, or three-phase systems with common voltage presets.
Open calculatorCharging time, cost, current, demand, and feeder planning
EV Charging Time and Cost Calculator
Estimate EV charging time, delivered energy, wall energy, and cost from battery state of charge and charger power.
Open calculatorPV strings, batteries, inverters, UPS, charging, and backup energy
Battery Charging Time Calculator
Calculate battery charging time from Ah and current or kWh and charger power, including charging efficiency.
Open calculatorCore formulas, phase power, resistance, circuits, and units
Series and Parallel Resistor Calculator
Calculate equivalent resistance, current, and voltage or current division for up to four resistors.
Open calculatorCore formulas, phase power, resistance, circuits, and units
Electrical Unit Converter
Convert power and energy units in either direction, or calculate DC, single-phase, and three-phase current from power.
Open calculatorMotor current, starting, contactors, voltage quality, and VFDs
Contactor Selection Calculator (AC-1 / AC-3)
Estimate a contactor current class from load type, power, voltage, utilization category, and operating frequency.
Open calculatorBreakers, fuses, fault current, grounding, and arc flash
Circuit Breaker Selectivity and Cascading Checker
Screen upstream and downstream breaker rating, curve, breaking capacity, and fault-current coordination.
Open calculatorLightning exposure, SPD selection, coordination, and backup protection
Lightning Risk Assessment Calculator
Estimate a simplified lightning exposure score from building collection area, location, thunderstorm activity, and incoming lines.
Open calculatorPanel heat, terminals, clearances, creepage, and enclosure ratings
Enclosure Cooling & Temperature Rise Calculator
Calculate enclosure internal temperature, required fan airflow, or active cooling capacity from cabinet size, heat load, ambient conditions, insulation, solar load, and protection requirements.
Open calculatorPanel heat, terminals, clearances, creepage, and enclosure ratings
Panel Component Heat Loss Calculator
Add breaker, contactor, drive, power-supply, transformer, and miscellaneous losses to estimate total cabinet heat load.
Open calculatorPV strings, batteries, inverters, UPS, charging, and backup energy
PV String Sizing Calculator
Calculate temperature-corrected PV string voltage and the allowable module count for an inverter MPPT window.
Open calculatorPV strings, batteries, inverters, UPS, charging, and backup energy
Off-Grid Solar System Sizing Calculator
Estimate PV array, battery-bank capacity, and inverter power from daily energy, sun hours, autonomy, and system voltage.
Open calculatorLightning exposure, SPD selection, coordination, and backup protection
SPD Backup Fuse Selection Calculator
Screen an SPD backup fuse or MCB rating from the SPD datasheet maximum backup protection and prospective fault current.
Open calculatorBreakers, fuses, fault current, grounding, and arc flash
Earth Fault Loop Impedance Calculator (Zs)
Calculate actual earth fault loop impedance and compare it with a device-based maximum Zs input.
Open calculatorConductor size, ampacity, voltage drop, and fault withstand
Cable Derating Factor Calculator
Combine ambient-temperature, grouping, installation, and soil factors to estimate corrected cable ampacity.
Open calculatorTransformers, demand, ATS, busbars, power quality, and generators
Maximum Demand and Diversity Calculator
Combine lighting, socket, HVAC, motor, EV, and other loads with demand and simultaneity factors.
Open calculatorConductor size, ampacity, voltage drop, and fault withstand
Protective Conductor Size Calculator
Calculate minimum protective-conductor cross-section using the IEC adiabatic equation and a user-selected material k value.
Open calculatorConductor size, ampacity, voltage drop, and fault withstand
Cable Short-Circuit Thermal Withstand Calculator
Check cable short-circuit thermal withstand using conductor area, fault current, duration, and material k value.
Open calculatorMotor current, starting, contactors, voltage quality, and VFDs
Motor Starting Voltage Drop Calculator
Estimate bus voltage dip during motor starting from motor current, starting method, transformer impedance, and feeder impedance.
Open calculatorMotor current, starting, contactors, voltage quality, and VFDs
VFD Sizing, Protection and Panel Calculator
Estimate the minimum VFD output-current class and screen input protection, bypass contactor, filtering, braking, and panel heat requirements.
Open calculatorBreakers, fuses, fault current, grounding, and arc flash
Arc Flash Incident Energy Calculator – IEEE 1584-2018
Calculate IEEE 1584-2018 arcing current, incident energy, and arc-flash boundary for normal and reduced-current clearing-time scenarios.
Open calculatorLux, lumens, fixtures, circuits, efficiency, and emergency lighting
Lighting Calculator: Lux, Lumens and Fixtures
Calculate required lumens, LED fixture quantity, achieved illuminance, connected watts, current, and preliminary lighting-circuit count.
Open calculatorConduit, tray, glands, lugs, routing, and cable entry
Cable Tray Fill and Sizing Calculator
Calculate cable tray area fill, single-layer width, reserve capacity, remaining space, cable weight, and a preliminary tray-width requirement.
Open calculatorPV strings, batteries, inverters, UPS, charging, and backup energy
Stationary Battery and DC System Sizing Calculator
Estimate stationary battery Ah, cell count, bank energy, parallel strings, peak discharge rate, charger current, and DC protection current.
Open calculatorTransformers, demand, ATS, busbars, power quality, and generators
Residential Electrical Load and Service Size Calculator
Estimate dwelling demand, service current, standard service size, spare capacity, and EV charging impact using NEC screening or user-entered demand factors.
Open calculatorPanel heat, terminals, clearances, creepage, and enclosure ratings
NEMA and IP Enclosure Rating Converter
Decode IEC IP ratings, cross-reference NEMA enclosure Types to IP protection, and screen enclosure Types from location, water, dust, corrosion, oil, ice, and immersion exposure.
Open calculatorMotor current, starting, contactors, voltage quality, and VFDs
Solid State Relay Selection & Heatsink Calculator
Calculate SSR load current, minimum nameplate-current screen, conduction loss, heatsink thermal resistance, junction temperature, surge margin, and semiconductor-fuse I²t checks.
Open calculatorBrowse by task
Choose an electrical calculator category.
Electrical Fundamentals & Circuit Analysis
Core formulas, phase power, resistance, circuits, and units
→Cable, Wire & Voltage Drop Tools
Conductor size, ampacity, voltage drop, and fault withstand
→Cable Management & Installation
Conduit, tray, glands, lugs, routing, and cable entry
→Circuit Protection & Grounding
Breakers, fuses, fault current, grounding, and arc flash
→Power Systems & Distribution
Transformers, demand, ATS, busbars, power quality, and generators
→Panels, Enclosures & Thermal
Panel heat, terminals, clearances, creepage, and enclosure ratings
→Motors, Contactors & Drives
Motor current, starting, contactors, voltage quality, and VFDs
→Solar, Battery & Backup Power
PV strings, batteries, inverters, UPS, charging, and backup energy
→Surge & Lightning Protection Tools
Lightning exposure, SPD selection, coordination, and backup protection
→EV Charging Tools
Charging time, cost, current, demand, and feeder planning
→Lighting Design
Lux, lumens, fixtures, circuits, efficiency, and emergency lighting
→Factory selection support
ContactNeed a product recommendation after the calculation?
Send the result to VIOX for SPD, MCB, MCCB, RCBO, contactor, cable gland, busbar, and EV charging protection support.