Electrical Tools

⚡ Quick Presets — Common NEC Services EV L2 32A EV L2 40A EV L2 48A 50A Subpanel 100A Subpanel 200A Service 30A Dryer 40A Range 10 HP Motor 25 HP Motor ⚡ Resistive / General Load ⚙ Motor Branch Circuit (NEC 430) Load Amps (A) Load Power (kW, optional) Leave blank if entering amps directly. System Voltage (V) 120 V 208 V 220 V 240 V 277 V 347 V 380 V 480 V 600 V Phase 1Φ Single-Phase 3Φ Three-Phase Power Factor (cosφ) Resistive load = 1.0. Motor load = 0.85 typical. Continuous load (NEC 210.20(A) — 125% rule) Required for EV chargers, solar PV inverters, and any load expected to run > 3 hours. Motor Power (HP) NEMA/IEC Design Letter B — Standard (most common, 250% FLA) A — High torque, normal locked-rotor (250% FLA) C — High starting torque (150% FLA) E — IEC premium efficiency (150% FLA) D — Very high locked-rotor (150% FLA) Motor Voltage (V) 115 V 208 V 220 V 230 V 240 V 380 V 460 V 480 V 575 V 600 V Motor Phase 1Φ Single-Phase 3Φ Three-Phase FLA is looked up from NEC Table 430.250 (3Φ) or 430.6 (1Φ). Per NEC 430.52, inverse-time breaker = 250% of FLA for Design A/B; 150% for Design C/E/D. Recommended OCPD — amperes Running Amps — A Design Amps — A Calculation Details Run current — NEC 210.20(A) 125% rule — NEC 240.4(B) round-up — NEC 240.6(A) standard rating — Enter load values to see the formula. 📊 NEC 240.6(A) Standard OCPD Sizes (click to expand) Standard OCPD (A)Common Use 15General lighting, 14 AWG 20General receptacles, 12 AWG 25Select appliances 30Dryer (small), water heater, 10 AWG 35Limited use 40Range (small), 8 AWG 45Limited use 50Subpanel feeders, 6 AWG, hot tub 60EV L2 48A continuous, 6 AWG 70Limited use 80Subpanel feeders 90Subpanel feeders 100Subpanel feeders, 3 AWG 110Service entrance 125Service entrance, 1/0 AWG 150Service entrance 175Service entrance, 2/0 AWG 200Residential service, 3/0 AWG 225Service entrance 250Commercial service 300Commercial service 350Commercial service 400Commercial service 450Industrial service 500Industrial service 600Industrial service 700Industrial service 800Industrial service Source: NFPA 70 — National Electrical Code 2023, Section 240.6(A). 📊 NEC Table 430.250 — 3-Phase Motor FLA Reference (click to expand) HP208 V230 V460 V 0.52.42.21.1 0.753.53.21.6 14.64.22.1 1.56.66.03.0 27.56.83.4 310.69.64.8 516.715.27.6 7.524.222.011.0 1030.828.014.0 1546.242.021.0 2059.454.027.0 2574.868.034.0 3088.080.040.0 40114.0104.052.0 50143.0130.065.0 60169.0154.077.0 75211.0192.096.0 100273.0248.0124.0 Source: NFPA 70 — National Electrical Code 2023, Table 430.250 (3-phase induction motors, full-load amperes). ⚠️ Reference only. OCPD sizing is NEC-aware but final conductor and breaker sizing must be verified by a licensed electrician and approved by your local Authority Having Jurisdiction (AHJ). Always follow the latest edition of NFPA 70 — National Electrical Code. TL;DR — What this calculator returns. Enter load amps or kW (resistive / general), or motor HP (NEC 430 branch circuit) — the tool returns the recommended overcurrent protective device (OCPD / breaker) sized per NEC 240.6(A) standard ratings, with NEC 240.4(B) next-larger OCPD logic when no standard OCPD matches the conductor ampacity, and the NEC 210.20(A) / 215.3 / 625 125 % continuous-load rule applied automatically when the load runs more than 3 hours. For motor branch circuits, the tool follows NEC 430.52 (inverse-time breaker = 250 % of FLA for NEMA Design A/B, 150 % for Design C/E). 100 % client-side, no signup, no upload. ...

⚡ Quick Presets — One-Click Sizing EV Charger 40A (continuous) EV Charger 48A (continuous) EV Charger 50A (continuous) 50A Subpanel 100A Subpanel 200A Service 30A Dryer 40A Range Load Amps (A) System Voltage (V) 120 V 208 V 220 V 240 V 277 V 347 V 480 V 600 V Phase 1Φ Single-Phase 3Φ Three-Phase One-Way Length (ft) Wire Material Copper (Cu) Aluminum (Al) Ambient Temp (°C) Current-Carrying Conductors 1 2-3 4-6 7-9 10-20 21-30 31-40 Continuous load (NEC 210.20(A) — 125% rule) Required for EV chargers, solar PV inverters, and any load expected to run > 3 hours. Conductor — — Breaker (OCPD) — amperes Voltage Drop — — Calculation Details Design amps (NEC 125% if continuous) — Base ampacity (NEC 310.16, 75°C) — Temperature correction (310.15(B)(1)) — Conduit-fill derating (310.15(C)(1)) — Final corrected ampacity — NEC 240.4(B) round-up applied Yes — bumped to match OCPD Enter load values to see the formula. 📊 NEC 310.16 Reference Table — 75°C Column (click to expand) AWG / kcmilCopper (A)Aluminum (A)Ω/1000 ft (Cu) 14 AWG20—3.14 12 AWG25—1.98 10 AWG35—1.24 8 AWG50400.778 6 AWG65500.491 4 AWG85650.308 3 AWG100750.245 2 AWG115900.194 1 AWG1301000.154 1/0 AWG1501200.122 2/0 AWG1751350.0967 3/0 AWG2001550.0766 4/0 AWG2301800.0608 250 kcmil2552050.0515 300 kcmil2852300.0429 350 kcmil3102500.0367 400 kcmil3352700.0321 500 kcmil3803100.0258 600 kcmil4203400.0214 750 kcmil4753850.0171 Source: NFPA 70 — National Electrical Code 2023, Table 310.16 (75°C column, the inspector-favored terminal rating per NEC 110.14(C) for circuits rated 100 A or less). ⚠️ Reference only. Calculations are NEC-aware but final conductor sizing must be verified by a licensed electrician and approved by your local Authority Having Jurisdiction (AHJ). Always follow the latest edition of NFPA 70 — National Electrical Code. TL;DR — What this calculator returns. Enter load amps (or use a preset), system voltage, one-way run length, wire material (copper / aluminum), ambient temperature, and number of current-carrying conductors. The tool returns the smallest NEC Table 310.16 (75 °C column) compliant AWG or kcmil, the corrected ampacity after NEC 310.15(B)(1) temperature and NEC 310.15(C)(1) conduit-fill adjustment, the recommended breaker (NEC 240.6(A) standard OCPD), and the voltage-drop % against the NEC 3 % branch / 5 % combined limits. ...