Electrical calculators & templates

Single-line and wiring diagrams from a library of electrical symbols, with templates and PDF export.

House electrical plans on a floor plan background, set to scale, with receptacles, switches, lights and a legend.

Lighting plans and reflected ceiling plans with fixtures, switch legs, a fixture schedule and a legend.

Watts to amps for DC, single-phase and three-phase loads at US voltages, with power factor and the working shown.

Amps to watts from a measured or rated current, for DC, single-phase and three-phase circuits.

Kilowatts to amps for heaters, EV chargers and three-phase equipment, with line-to-neutral voltage entry.

Amps to kilowatts for services, feeders and metered loads at 120, 208, 240 and 480 V.

Full-load amps of transformers, generators and UPS units from their kVA rating and voltage.

Amps to kVA for comparing a load with a transformer, generator or UPS rating.

kVA to kW and kW to kVA at any power factor, with the reactive power in kVAR.

Horsepower to kW and kW to hp in mechanical, electrical and metric horsepower, with motor efficiency.

Fixture count by the spacing rule and the lumen method, spacing from the walls and a layout drawn to scale.

Minimum wire size by ampacity and by voltage drop, the recommended size and the NEC 240.4(D) limits.

AWG 4/0 to 40 from the gauge definition: diameter, area in kcmil and mm², copper and aluminum resistance.

Copper and aluminum wire size for 20 A at 60 °C and 75 °C, kitchen, bathroom and laundry circuits and voltage drop.

Copper and aluminum wire size for 30 A at 60 °C and 75 °C, dryer and water heater circuits and voltage drop.

Copper and aluminum wire size for 40 A at 60 °C and 75 °C, range and EV charger circuits and voltage drop.

Copper and aluminum wire size for 50 A at 60 °C and 75 °C, range, RV, EV and subpanel circuits and voltage drop.

Copper and aluminum wire size for 60 A at 60 °C and 75 °C, subpanel, hot tub and EV charger circuits and voltage drop.

Copper and aluminum wire size for 100 A at 60 °C and 75 °C, dwelling services and subpanel feeders and voltage drop.

Copper and aluminum wire size for 150 A at 60 °C and 75 °C, dwelling services and subpanel feeders and voltage drop.

Copper and aluminum wire size for 200 A at 60 °C and 75 °C, dwelling services and feeders and voltage drop.

The standard ampere ratings of NEC 240.6(A), next size up, and common residential breakers with their wire.

Free Ohm's law calculator: get current, power, voltage and resistance from voltage, resistance, current and power. The formula is shown; verify against the NEC.

Free voltage drop calculator: get voltage drop from voltage, current, one-way cable length, conductor area and resistivity at operating temperature.

Free solar wire size calculator: get minimum area (drop only) from voltage, current, one-way cable length and resistivity at operating temperature.

Free conductor sizing calculator: get minimum area (drop only) from voltage, current, one-way cable length and resistivity at operating temperature.

Free distributed load conductor sizing calculator: get minimum area (drop only) from voltage, current and one-way cable length. With the formula shown.

Free HP to amps calculator: get estimated current from mechanical output, voltage, power factor, efficiency and current. With the formula shown.

Free motor FLA calculator: get estimated full-load current from output power, voltage and power factor. The formula is shown; verify against the NEC.

Free motor service factor calculator: get service factor current from current, rated output, nameplate service factor and verified overload multiplier.

Free conduit fill calculator: get fill and minimum internal diameter from conductor count, outside conductor diameter and internal conduit diameter.

Free conduit bending calculator: get bend spacing and offset shrink from offset rise, rolling offset, bend angle, stub height and bender take-up.

Free box fill calculator: get required volume from verified conductor equivalents, volume per equivalent, available box volume and non-ground conductor count.

Free generator sizing calculator: get peak load and design capacity from total simultaneous running load, largest additional starting surge and reserve margin.

Free transformer sizing calculator: get load apparent power from secondary (load) voltage, current, primary voltage, growth allowance and design loading target.

Free breaker size calculator: get minimum rating (125% continuous + noncontinuous) from continuous load current, noncontinuous load current and continuous load.

Free fuse size calculator: get calculated maximum (flc × 175%) from motor flc from nec tables 430.247–430.250 (not nameplate). With the formula shown.

Free ampacity calculator: get temperature correction factor (equation 310.15(b)). The formula and a worked example are shown; verify against the NEC.

Free current calculator: get current from active power, voltage and power factor. The formula and a worked example are shown; verify against the NEC.

Free voltage calculator: get voltage from active power, current and power factor. The formula and a worked example are shown; verify against the NEC.

Free active power calculator: get active power from voltage, current and power factor. The formula and a worked example are shown; verify against the NEC.

Free apparent power calculator: get apparent power from voltage and current. The formula and a worked example are shown; verify against the NEC.

Free reactive power calculator: get reactive power from apparent power and power factor. The formula and a worked example are shown; verify against the NEC.

Free power factor calculator: get power factor from active power and apparent power. The formula and a worked example are shown; verify against the NEC.

Free resistance calculator for electricians, with clear inputs, an instant result, the equation behind it and a worked example. Verify against the NEC.

Free impedance from resistance and reactance: get impedance and phase angle from resistance and reactance magnitude. With the formula shown.

Free reactance calculator: get inductive reactance and capacitive reactance from frequency, inductance and capacitance. With the formula shown.

Free maximum wire length (voltage drop): get maximum one-way length from voltage, current, conductor area, resistivity at operating temperature and drop limit.

Free maximum wire length (short-circuit): get maximum resistive loop length from voltage, required fault current for disconnection and external loop impedance.

Free wire resistance calculator for copper and aluminum by AWG or kcmil: resistance and conductance by length and temperature, with K values shown.

Free cable temperature from resistance: get estimated conductor temperature from reference resistance, measured resistance and reference temperature.

Free power losses in cables: get power loss from current, resistance per conductor and loaded conductors. The formula is shown; verify against the NEC.

Free neutral current calculator: get fundamental neutral current from phase a current, phase b current and phase c current. With the formula shown.

Free voltage drop with distributed loads: get drop from voltage, current, one-way cable length, conductor area and resistivity at operating temperature.

Free design current calculator: get design current from connected load, voltage, power factor and verified demand factor. With the formula shown.

Free power factor correction calculator: get compensation required from active load, initial power factor and target power factor. With the formula shown.

Free transformer power factor correction calculator: get compensation required from active load, initial power factor and target power factor.

Free capacitor power at a different voltage: get reactive power at operating voltage from rated reactive power, rated voltage and operating voltage.

Free Short-circuit current at a point: get prospective fault current from voltage and verified equivalent source + line impedance. With the formula shown.

Free available fault current calculator: transformer kVA, %Z and voltage, then the point-to-point method along the conductor, with working shown.

Free minimum short-circuit current: get minimum fault current estimate from line-to-ground voltage and verified minimum voltage factor. With the formula shown.

Free cable protection from short-circuit: get cable withstand from conductor area, verified material/insulation k factor, fault current and disconnection time.

Free admissible specific energy of cable (k²S²): get cable withstand from conductor area, verified material/insulation k factor and fault current.

Free motor current, voltage and power calculator: get motor current from shaft output, voltage, current, power factor and efficiency. With the formula shown.

Free motor power factor calculator: get power factor from input active power, voltage and current. The formula is shown; verify against the NEC.

Free motor efficiency calculator: get efficiency from measured shaft power and measured electrical input. The formula is shown; verify against the NEC.

Free Single-phase motor run capacitor: get equivalent capacitance from measured capacitor current, measured capacitor voltage and frequency.

Free motor synchronous speed calculator: get synchronous speed from frequency and number of poles. The formula is shown; verify against the NEC.

Free motor slip calculator: get slip from synchronous speed and rotor speed. The formula and a worked example are shown; verify against the NEC.

Free power and motor torque calculator: get rated operating torque from mechanical output and shaft speed. The formula is shown; verify against the NEC.

Free resistor for LED calculator: get series resistor and resistor dissipation from supply voltage, led forward voltage, led current and leds in series.

Free voltage divider calculator: get unloaded output from voltage, upper resistance and lower resistance. The formula is shown; verify against the NEC.

Free resistor to reduce voltage: get series resistance and dissipation from input voltage, desired load voltage and current. With the formula shown.

Free current divider calculator: get branch 1 and branch 2 from current, branch 1 resistance and branch 2 resistance. With the formula shown.

Free sum of resistors calculator: get series from resistance 1 and resistance 2. The formula and a worked example are shown; verify against the NEC.

Free sum of capacitors calculator: get parallel and series from capacitance 1 and capacitance 2. The formula is shown; verify against the NEC.

Free resonant frequency calculator: get resonant frequency from inductance and capacitance. The formula and a worked example are shown; verify against the NEC.

Free battery life calculator: get estimated runtime from battery capacity, load current, usable capacity and efficiency. With the formula shown.

Free primary and secondary transformer winding: get secondary turns and turns ratio from primary turns, primary voltage and secondary voltage.

Free antenna length calculator: get wavelength, quarter wave and half wave from frequency and velocity factor. The formula is shown; verify against the NEC.

Free CCTV hard disk and bandwidth sizing: get storage incl. overhead from cameras, bitrate per camera, retention, recording per day and storage overhead.

Free analog signal range converter: get scaled output from input value, input minimum, input maximum, output minimum and output maximum. With the formula shown.

Free joule effect calculator: get heat energy and power from current, resistance and duration. The formula is shown; verify against the NEC.

Free zener voltage stabilizer calculator: get series resistance, zener dissipation and series resistor dissipation from input voltage and zener voltage.

Free resistor and inductor color code calculator for electricians, with clear inputs, an instant result, the equation behind it and a worked example. Verify.

Free resistor colors from value: get first band digit, second band digit and multiplier exponent from resistance. The formula is shown; verify against the NEC.

Free SMD resistor code decoder: get decoded value from three-digit numeric code. The formula and a worked example are shown; verify against the NEC.

Free capacitor code decoder: get decoded value from three-digit numeric code. The formula and a worked example are shown; verify against the NEC.

Free inductor numeric code decoder: get decoded value from three-digit numeric code. The formula and a worked example are shown; verify against the NEC.

Free EV charging time calculator: get estimated charging time from battery capacity, starting charge, target charge, charger output and efficiency.

Free electricity cost calculator: get energy and cost from load power, use per day, number of days and price per kwh. With the formula shown.

Free solar battery capacity calculator: get nominal battery capacity from daily energy, autonomy, usable depth of discharge, efficiency and voltage.

Free electrical unit converter: get mechanical power, length and awg conductor area from horsepower, length and awg gauge. With the formula shown.

Reference guide to conductor and protective device coordination: the checks to work through and when to verify against the NEC and the manufacturer's data.

Reference guide to motor full-load current (NEC): 4 checks to work through, the limits that apply and when to verify against the NEC and maker data.

Reference guide to motor from three-phase to single-phase: 4 checks to work through, the limits that apply and when to verify against the NEC and maker data.

Reference guide to 3-phase motor wiring (6 terminals): 3 checks to work through, the limits that apply and when to verify against the NEC and maker data.

Reference guide to 3-phase motor wiring (9 terminals): 3 checks to work through, the limits that apply and when to verify against the NEC and maker data.

Reference guide to 3-phase motor wiring (12 terminals): 3 checks to work through, the limits that apply and when to verify against the NEC and maker data.

Reference guide to motor connections reference: 3 checks to work through, the limits that apply and when to verify against the NEC and maker data.

Reference guide to motor terminals marking for electricians: 3 checks to work through, the limits that apply and when to verify against the NEC and maker data.

Reference guide to insulation class of the motor: 3 checks to work through, the limits that apply and when to verify against the NEC and maker data.

Reference guide to current carrying capacity of insulated conductors: the checks to work through and when to verify against the NEC and the manufacturer's data.

Reference guide to bare and mineral-insulated conductor ampacity: the checks to work through and when to verify against the NEC and the manufacturer's data.

Reference guide to busbar current carrying capacity: 3 checks to work through, the limits that apply and when to verify against the NEC and maker data.

Reference guide to conduit and cable tray sizing: 3 checks to work through, the limits that apply and when to verify against the NEC and maker data.

Reference guide to fuse markings and types for electricians: 3 checks to work through, the limits that apply and when to verify against the NEC and maker data.

Reference guide to table of capacitor codes for electricians: 3 checks to work through, the limits that apply and when to verify against the NEC and maker data.

Reference guide to temperature sensors (PT/NI/CU, NTC, thermocouples): the checks to work through, the limits that apply and when to verify against the NEC.

Reference guide to atmospheric overvoltage risk assessment: 3 checks to work through, the limits that apply and when to verify against the NEC and maker data.

Reference guide to protection for emergency lighting lines: 3 checks to work through, the limits that apply and when to verify against the NEC and maker data.