Electrical Calculators

Use these tools for rough planning and field checks. Final designs still require the current NEC edition adopted by the local AHJ, equipment listings and markings, nameplates, site conditions, and professional judgment.

Ampacity and Derating Calculator Start with required amps and get practical standard conductor options, then expand for derating details.

This tool starts with NEC Table 310.16 reference values for not more than three current-carrying conductors at 30°C. A 90°C insulation column may be used for adjustment and correction math where permitted, but it is not automatically the final allowable ampacity.

Quick mode uses the settings shown below. Leave the defaults when you only need a conservative starting point, or expand the advanced settings for ambient temperature, current-carrying conductor count, NM-B, rooftop, and exact-size checks.

Quick Ampacity Finder

Required ampacity

Conductor material

Insulation / conductor type

Equipment terminal temperature

Advanced ampacity settings and exact-size check

Check exact gauge / kcmil (optional)

Ambient temperature (°C)

Current-carrying conductors

Raceway / cable / bundle context

Treat this as NM cable / Romex and cap the final result at the 60°C column.

Add the 33°C rooftop sunlight temperature adder when the current NEC rooftop condition applies.

Use conservative residential mode: do not treat a selected 90°C terminal as an ordinary final ampacity cap.

Power and Ohm's Law Calculator Quick PIER field math plus advanced single-phase and three-phase AC power calculations.

Fill in any two positive PIER values to calculate the other two. Use the advanced section for AC loads, kVA, power factor, and reactive power.

Quick PIER Calculator

Power (P, watts)

Current (I, amps)

Voltage / EMF (E, volts)

Resistance (R, ohms)

Advanced AC power, kVA, and power factor

Enter a useful combination such as volts + amps + power factor, kW + kVA, or kVA + power factor + volts. The calculator fills the remaining critical values.

System phase

Voltage (V)

Current (A)

Power factor (0 to 1)

Real power (kW)

Apparent power (kVA)

Conduit Bend Offset Calculator Calculate bend spacing for common conduit offsets.

Enter the offset height and bend angle. Confirm the bender take-up and field conditions before bending.

Offset height (inches)

Bend angle

Service Load Planning Calculator Mode-based early planning for homes, additions, workshops, small commercial spaces, and commercial kitchens.

This calculator is deliberately conservative and transparent. It is an early planning tool, not a sealed design, a permit calculation, or a substitute for a complete NEC Article 220 worksheet.

Calculation mode

Project profile

General Inputs

Area (sq ft)

Lighting scenario

Small-appliance circuits (1,500 VA each)

Laundry circuits (1,500 VA each)

Appliances and Added Loads

Clothes dryer

Clothes washer

Cooking equipment

Water heater

EV charger

Dishwasher

Microwave

Other loads (VA)

Heating and Cooling

Heating system

Cooling system

Supplemental / backup electric heat (VA)

HVAC relationship

Service Output

Selected voltage

Phase

Lighting Area Calculator Estimate room lumens and per-fixture output.

Uses 50 lumens per square foot as a general planning guideline. Adjust for the room use, finishes, fixture type, and customer preference.

Room length (ft)

Room width (ft)

Number of fixtures

Heating Sizing Calculator Estimate room heating capacity for early planning.

Uses 10 watts per square foot as a rough starting point. Confirm heat loss, insulation, windows, climate, and equipment instructions before selection.

Area length (ft)

Area width (ft)