Electrical Calculator
Select a calculator from the menu above to get started.
Wire & Ampacity Sizing (NEC 310)
Based on NEC Table 310.16. Enter load current and conditions to find required wire size.
Wire Sizing Result
| Required Ampacity | |
| Recommended Wire Size | |
| Wire Ampacity (adjusted) | |
| Temp Correction Factor | |
| Bundle Derating Factor |
Quick Reference — NEC 310.16 Ampacity
| AWG / kcmil | Cu 60°C | Cu 75°C | Cu 90°C | Al 75°C | Al 90°C |
|---|---|---|---|---|---|
| 14 AWG | 15 | 20 | 25 | — | — |
| 12 AWG | 20 | 25 | 30 | 20 | 25 |
| 10 AWG | 30 | 35 | 40 | 30 | 35 |
| 8 AWG | 40 | 50 | 55 | 40 | 45 |
| 6 AWG | 55 | 65 | 75 | 50 | 60 |
| 4 AWG | 70 | 85 | 95 | 65 | 75 |
| 3 AWG | 85 | 100 | 110 | 75 | 85 |
| 2 AWG | 95 | 115 | 130 | 90 | 100 |
| 1 AWG | 110 | 130 | 150 | 100 | 115 |
| 1/0 AWG | 125 | 150 | 170 | 120 | 135 |
| 2/0 AWG | 145 | 175 | 195 | 135 | 150 |
| 3/0 AWG | 165 | 200 | 225 | 155 | 175 |
| 4/0 AWG | 195 | 230 | 260 | 180 | 205 |
| 250 kcmil | 215 | 255 | 290 | 205 | 230 |
| 300 kcmil | 240 | 285 | 320 | 230 | 260 |
| 350 kcmil | 260 | 310 | 350 | 250 | 280 |
| 400 kcmil | 280 | 335 | 380 | 270 | 305 |
| 500 kcmil | 320 | 380 | 430 | 310 | 350 |
Voltage Drop Calculator
NEC recommends max 3% VD for branch circuits, 5% total (feeder + branch).
Voltage Drop Result
| Voltage Drop | |
| % Voltage Drop | |
| Receiving End Voltage |
Min Wire Size for <3% VD
Minimum Wire Size Result
Residential Service Load Calculation (NEC 220)
Standard method per NEC 220.82. Enter square footage and appliances to size service.
General Lighting & Receptacles
Fixed Appliances (Watts)
Heating & Cooling (enter largest)
Service
Service Load Result
| General Lighting Load | |
| Small Appliance Load | |
| Laundry Circuit | |
| Subtotal (before demand) | |
| Demand Factor Applied | |
| Fixed Appliance Load | |
| Largest HVAC Load | |
| TOTAL CALCULATED LOAD | |
| Required Service Amps | |
| Recommended Service Size |
Conduit Fill Calculator (NEC 358/344/358)
NEC fill: 1 wire = 53%, 2 wires = 31%, 3+ wires = 40% of conduit area.
Conductors
| Wire Size | Insulation | Quantity | Area (in²) ea |
|---|---|---|---|
| 0.0097 |
Conduit Fill Result
| Conduit Internal Area | |
| Total Wire Area | |
| Fill Percentage | |
| Max Allowed Fill | |
| Wires Remaining |
Motor Circuit Calculator (NEC 430)
Sizes branch circuit wire, breaker, and overload protection per NEC 430.
Motor Circuit Result
| Full Load Amps (FLA) | |
| Min Branch Circuit Wire | |
| Wire Ampacity Required | |
| Max Breaker / Fuse Size | |
| Overload Protection Max | |
| Disconnecting Means Min |
Power & Ohm's Law
Enter any two known values — the calculator will find the rest.
Power & Ohm's Law Result
| Voltage (V) | |
| Current (A) | |
| Resistance (Ω) | |
| True Power (W) | |
| Apparent Power (VA) | |
| Reactive Power (VAR) | |
| Kilowatts (kW) | |
| kVA |
Electrical Materials List
Enter quantities and unit costs to build a materials estimate.
| Item / Description | Qty | Unit | Unit Cost | Total |
|---|---|---|---|---|
| $0.00 |
Materials Summary
| Materials Subtotal | |
| Tax (enter %) | % |
| Tax Amount | |
| TOTAL MATERIALS |
Labor Estimator
Labor Hours
| Task | Unit | Qty | Hrs/Unit | Hours |
|---|---|---|---|---|
| 1.00 |
Rates
Labor Summary
| Total Task Hours | |
| Journeyman Cost | |
| Apprentice Cost | |
| Direct Labor Cost | |
| Overhead & Burden | |
| Labor Subtotal | |
| Profit | |
| TOTAL LABOR COST |
Bid & Financial Summary
Bid Summary
| Materials (+ tax) | |
| Labor | |
| Subcontractors | |
| Equipment | |
| Permits | |
| Direct Cost | |
| Overhead | |
| Contingency | |
| Bond / Insurance | |
| Profit | |
| BID PRICE | |
| Gross Margin | |
| Cost per $1 Billed |
Basic Calculator
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