Load Calculator
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Step 1 — Installation Type
Select the type of installation to begin the NEC compliance wizard.
Residential
NEC Article 210, 220, 230
Commercial
NEC Article 210, 215, 220
Industrial
NEC Article 430, 440, 450
Service Entrance
NEC Article 230
Motor Circuit
NEC Article 430
Solar / PV System
NEC Article 690
Conductor Ampacity — NEC Table 310.16
NEC 310.16 · 0–2000V, 60–75–90°C
| AWG/kcmil | Cu 60°C | Cu 75°C | Cu 90°C | Al 60°C | Al 75°C | Al 90°C |
|---|---|---|---|---|---|---|
| #14 | 15A | 20A | 25A | — | — | — |
| #12 | 20A | 25A | 30A | 15A | 20A | 25A |
| #10 | 30A | 35A | 40A | 25A | 30A | 35A |
| #8 | 40A | 50A | 55A | 30A | 40A | 45A |
| #6 | 55A | 65A | 75A | 40A | 50A | 60A |
| #4 | 70A | 85A | 95A | 55A | 65A | 75A |
| #3 | 85A | 100A | 110A | 65A | 75A | 85A |
| #2 | 95A | 115A | 130A | 75A | 90A | 100A |
| #1 | 110A | 130A | 150A | 85A | 100A | 115A |
| #1/0 | 125A | 150A | 170A | 100A | 120A | 135A |
| #2/0 | 145A | 175A | 195A | 115A | 135A | 150A |
| #3/0 | 165A | 200A | 225A | 130A | 155A | 175A |
| #4/0 | 195A | 230A | 260A | 150A | 180A | 205A |
| 250 kcmil | 215A | 255A | 290A | 170A | 205A | 230A |
| 300 kcmil | 240A | 285A | 320A | 195A | 230A | 260A |
| 350 kcmil | 260A | 310A | 350A | 210A | 250A | 280A |
| 400 kcmil | 280A | 335A | 380A | 225A | 270A | 305A |
| 500 kcmil | 320A | 380A | 430A | 260A | 310A | 350A |
| 600 kcmil | 355A | 420A | 475A | 285A | 340A | 385A |
⚠ When using 75°C rated terminals (most equipment), use the 75°C column even if conductor is rated 90°C. Always derate for ambient temperature and conduit fill per NEC 310.15(B).
Conduit Fill — NEC Chapter 9, Table 1
NEC Ch.9 Table 1 · EMT · RMC · PVC 40 · PVC 80
| Trade Size | 1 conductor (53%) | 2 conductors (31%) | 3+ conductors (40%) | EMT Area (in²) |
|---|---|---|---|---|
| ½" | 0.16 in² | 0.09 in² | 0.12 in² | 0.304 |
| ¾" | 0.26 in² | 0.15 in² | 0.20 in² | 0.533 |
| 1" | 0.43 in² | 0.25 in² | 0.35 in² | 0.864 |
| 1¼" | 0.76 in² | 0.44 in² | 0.60 in² | 1.496 |
| 1½" | 1.06 in² | 0.61 in² | 0.83 in² | 2.036 |
| 2" | 1.74 in² | 1.01 in² | 1.34 in² | 3.356 |
| 2½" | 3.08 in² | 1.79 in² | 2.31 in² | 5.858 |
| 3" | 4.61 in² | 2.68 in² | 3.46 in² | 8.846 |
| 3½" | 6.08 in² | 3.53 in² | 4.57 in² | 11.545 |
| 4" | 7.83 in² | 4.55 in² | 5.90 in² | 14.753 |
Conductor area reference: #14=0.0097, #12=0.0133, #10=0.0211, #8=0.0471, #6=0.0590, #4=0.0814, #2=0.1333, #1=0.1562, 1/0=0.1963, 2/0=0.2463, 3/0=0.3107, 4/0=0.3904 in²
Standard OCPD Ratings — NEC 240.6
NEC 240.6(A) · Standard ampere ratings
{['15','20','25','30','35','40','45','50','60','70','80','90','100','110','125','150','175','200','225','250','300','350','400','450','500','600','700','800','1000','1200','1600','2000','2500','3000','4000','5000','6000'].map(a=>`${a}A`).join('')}
Real-world field sizes (commonly stocked): 15, 20, 30, 40, 50, 60, 70, 100, 125, 150, 200, 225, 400, 600A. Sizes 25A, 35A, 45A, 90A, 110A exist per NEC 240.6(A) but are specialty/hard to find. 80% Rule (NEC 210.20): Continuous loads must not exceed 80% of breaker rating — size breaker at 125% of load. NEC 240.4(D): #14 Cu max 15A, #12 Cu max 20A, #10 Cu max 30A — regardless of load.
Equipment Grounding Conductor — NEC Table 250.122
NEC 250.122 · Based on OCPD rating
| OCPD Rating (A) | Cu EGC | Al EGC |
|---|---|---|
| 15 | #14 AWG | #12 AWG |
| 20 | #12 AWG | #10 AWG |
| 30–60 | #10 AWG | #8 AWG |
| 100 | #8 AWG | #6 AWG |
| 200 | #6 AWG | #4 AWG |
| 300–400 | #4 AWG | #2 AWG |
| 500–600 | #2 AWG | #1/0 AWG |
| 800 | #1/0 AWG | #3/0 AWG |
| 1000–1200 | #2/0 AWG | #4/0 AWG |
| 1600–2000 | #3/0 AWG | 250 kcmil |
Demand Factors — NEC Article 220
NEC 220.42, 220.50, 220.54, 220.55
| Load Type | Demand Factor | NEC Ref |
|---|---|---|
| Lighting — first 3,000 VA | 100% | 220.42 |
| Lighting — 3,001 to 120,000 VA | 35% | 220.42 |
| Lighting — over 120,000 VA | 25% | 220.42 |
| Small appliance circuits (residential) | 100% | 220.52 |
| Electric dryer — first 4 | 100% | 220.54 |
| Electric dryer — 5–23 units | 85–35% | 220.54 |
| Largest A/C or heating unit | 100% | 220.60 |
| Remaining A/C or heating | Use larger of the two loads | 220.60 |
| Motor loads | 125% of largest + 100% others | 430.24 |
NEC 220.60: Only the larger of the A/C or heating load needs to be calculated — not both simultaneously (they don't run at the same time).
Ambient Temperature Correction — NEC 310.15(B)(1)
NEC 310.15(B)(1) · Multiply ampacity by correction factor
| Ambient °C | Ambient °F | 60°C factor | 75°C factor | 90°C factor |
|---|---|---|---|---|
| 21–25°C | 70–77°F | 1.08 | 1.05 | 1.04 |
| 26–30°C | 78–86°F | 1.00 | 1.00 | 1.00 |
| 31–35°C | 87–95°F | 0.91 | 0.94 | 0.96 |
| 36–40°C | 96–104°F | 0.82 | 0.88 | 0.91 |
| 41–45°C | 105–113°F | 0.71 | 0.82 | 0.87 |
| 46–50°C | 114–122°F | 0.58 | 0.75 | 0.82 |
| 51–55°C | 123–131°F | 0.41 | 0.67 | 0.76 |
| 56–60°C | 132–140°F | — | 0.58 | 0.71 |
⚠ Puerto Rico: Outdoor ambient typically 35–40°C. Attics and direct sun exposure can reach 45–50°C. Always apply correction factor for PR installations.
Motor Circuit Requirements — NEC Article 430
NEC 430.22, 430.52, 430.32 · Branch circuit sizing
| Component | Multiplier | NEC Ref | Notes |
|---|---|---|---|
| Branch circuit conductor | FLA × 125% | 430.22 | Minimum ampacity |
| Overload protection | FLA × 115–125% | 430.32 | 115% SF≥1.15, 125% others |
| Inverse time breaker | FLA × 250% | 430.52(C) | Maximum OCPD |
| Instantaneous trip breaker | FLA × 800–1300% | 430.52(C) | Motor controller required |
| Dual-element fuse | FLA × 175% | 430.52(C) | Time-delay type |
| Multiple motors feeder | Largest × 125% + others × 100% | 430.24 | Feeder sizing |
Service Factor (SF): If the motor nameplate shows SF ≥ 1.15, overload protection can be set at 125% FLA. Otherwise 115% maximum.
AFCI & GFCI Requirements — NEC 210.8 / 210.12
NEC 210.8(A)(B) · 210.12(A)(B) · 2023 edition
| Location | GFCI Required | AFCI Required |
|---|---|---|
| Bathroom | ✅ Yes — 210.8(A)(1) | ✅ Yes — 210.12 |
| Kitchen (countertop) | ✅ Yes — 210.8(A)(6) | ✅ Yes — 210.12 |
| Garage | ✅ Yes — 210.8(A)(2) | ✅ Yes — 210.12 |
| Outdoors | ✅ Yes — 210.8(A)(3) | ❌ No |
| Basement (unfinished) | ✅ Yes — 210.8(A)(5) | ✅ Yes — 210.12 |
| Crawl space | ✅ Yes — 210.8(A)(4) | ❌ No |
| Bedroom | ❌ No (unless within 6ft of sink) | ✅ Yes — 210.12 |
| Living areas | ❌ No | ✅ Yes — 210.12 |
| Pool / spa | ✅ Yes — 680 | ❌ No |
| Commercial kitchens | ✅ Yes — 210.8(B) | Varies |
Conductor Color Code — NEC 200.6 / 210.5
NEC 200.6, 210.5(C) · Color identification
| Conductor | Required Color | System |
|---|---|---|
| Grounded (Neutral) | White or Gray | All systems |
| Equipment Ground (EGC) | Green, Green/Yellow, Bare | All systems |
| Ungrounded (Hot) Phase A | Black | All systems |
| Ungrounded (Hot) Phase B | Red | 120/240V or 208V 3Ø |
| Ungrounded (Hot) Phase C | Blue | 208V / 480V 3Ø |
| Hot — 277V (from 480V) | Brown | 480V Wye |
| Hot Phase B — 480V | Orange | 480V Wye |
| Hot Phase C — 480V | Yellow | 480V Wye |
| High-leg Delta (208V) | Orange | 240V Delta |
NEC does not mandate color for ungrounded conductors #6 AWG and larger — field marking with tape is acceptable. White re-identified with tape = ungrounded conductor ≥ #4 AWG (200.7(C)).
Box Fill Calculation — NEC 314.16
NEC 314.16(B) · Conductor volume allowances
| Wire Size | Volume per conductor (in³) |
|---|---|
| #18 AWG | 1.50 in³ |
| #16 AWG | 1.75 in³ |
| #14 AWG | 2.00 in³ |
| #12 AWG | 2.25 in³ |
| #10 AWG | 2.50 in³ |
| #8 AWG | 3.00 in³ |
| #6 AWG | 5.00 in³ |
Count: Each hot + neutral = 1 each. All grounds combined = 1. Device (receptacle/switch) = 2 conductors of largest wire. Cable clamps combined = 1. Internal cable clamps = 0 if cable connector is outside.
NEC Compliance Report
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