Electrical calculators and charts
Size a wire or a service, check conduit and box fill, convert watts to amps, or look up what an appliance draws and which breaker it needs.
Calculators
- Box fill calculatorCount the wires, devices, clamps and grounds in an electrical box and find the cubic inches it needs and the smallest standard box that fits.
- Conduit fill calculatorCheck how full a conduit is with any mix of THHN wires, or find the smallest EMT, PVC or rigid conduit that holds them.
- Electricity cost calculatorWork out how many kWh an appliance uses and what it costs to run per day, month and year from its watts, hours of use and your rate.
- kVA to amps calculatorConvert transformer or generator kVA to amps at 120/240 V single phase and 208, 240 or 480 V three phase, and amps back to kVA.
- Electrical load calculatorEstimate a house's electrical load from its floor area, appliances, heating and air conditioning, and the service size it needs in amps.
- Ohm's law calculatorEnter any two of volts, amps, ohms and watts to get the other two, with the formula and every step of the calculation.
- Watts to amps calculatorConvert watts to amps and amps to watts at 120, 240 or any voltage, single or three phase, with power factor for motors.
- Wire size calculatorFind the wire gauge for a circuit by amps, distance and voltage. Shows the voltage drop, the size required by ampacity and when a long run needs a larger wire.
Charts
- Ampacity chartAllowable amps for copper and aluminum conductors from 14 AWG to 600 kcmil at 60, 75 and 90 °C, with the small-conductor breaker limits.
- Appliance wattage chartRunning watts and amps of common household appliances at 120 and 240 V, with the breaker and circuit each one needs.
- AWG chartAmerican Wire Gauge sizes from 18 AWG to 600 kcmil: diameter in inches and millimeters, area in circular mils and mm², resistance per 1,000 ft.
- Breaker size chartLargest breaker for each wire size from 14 AWG to 600 kcmil, copper and aluminum, for NM-B cable and for 75 °C terminations.
- Conduit fill chartMaximum number of THHN wires from 14 AWG to 4/0 in EMT, PVC Schedule 40 and 80 and rigid conduit from 1/2 to 4 inches.
- Ground wire size chartMinimum equipment grounding conductor for every breaker from 15 to 1,200 amps, copper and aluminum, and how to size it on long runs.
- Extension cord gauge chartWhich extension cord gauge to use for a load from 5 to 15 amps at 25, 50, 100 and 150 feet, keeping the voltage drop within 5%.
- Generator wattage chartRunning and starting watts of household appliances and the generator size each one needs, from a refrigerator to central air.
- Motor FLA chartFull-load amps of single-phase and three-phase AC motors by horsepower and voltage, with the 125% conductor ampacity for the branch circuit.
- Voltage drop chartHow far each copper wire size can run at full load before the voltage drop passes 3%, at 120 and 240 volts.
- Wire gauge chartAWG wire sizes from 18 to 4/0 with diameter, cross-section, amps for copper NM-B cable and THHN, the largest breaker and what each size is used for.
- Wire size chartWire size for every standard breaker from 15 to 400 amps in copper and aluminum, for NM-B cable and for 75 °C terminations.
Wire size by breaker rating
Wire gauge amps
Service wire size
Sub panel wire size
Watts, amps and kVA conversions
- 100 watts to amps
- 500 watts to amps
- 1000 watts to amps
- 1500 watts to amps
- 2000 watts to amps
- 3000 watts to amps
- 5000 watts to amps
- 1 amp to watts
- 5 amps to watts
- 10 amps to watts
- 15 amps to watts
- 20 amps to watts
- 30 amps to watts
- 50 amps to watts
- 5 kW to amps
- 10 kW to amps
- 20 kW to amps
- 50 kW to amps
- 100 kW to amps
- 15 kVA to amps
- 30 kVA to amps
- 45 kVA to amps
- 75 kVA to amps
- 100 kVA to amps
- 150 kVA to amps
Appliance power use
- Air Fryer
- Ceiling Fan
- Central Air Conditioner
- Circular Saw
- Coffee Maker
- Computer Monitor
- CPAP Machine
- Crock Pot
- Dehumidifier
- Desktop Computer
- Dishwasher
- Electric Blanket
- Electric Dryer
- Electric Oven
- Electric Range
- Electric Water Heater
- Fan
- Furnace
- Gaming PC
- Garbage Disposal
- Gas Stove
- Hair Dryer
- Heat Pump
- Hot Tub
- House
- Laptop
- Light Bulb
- Microwave
- Mini Fridge
- Mini Split
- Phone Charger
- Pool Pump
- Portable Air Conditioner
- Power Tool Battery Charger
- PS5
- Refrigerator
- RV Air Conditioner
- Space Heater
- Starlink Dish
- Sump Pump
- Toaster
- TV
- Washing Machine
- Welder
- Well Pump
- Window Air Conditioner
- Xbox