Free Electrical Tools
Professional electrical calculation tools for NEC compliance. All tools are free, accurate, and designed for electricians.
Box Fill CalculatorMost Popular
Calculate electrical box fill per NEC 314.16. The most accurate and easy-to-use box fill calculator online.
Wire Gauge Chart
Complete AWG wire gauge chart with conductor volume allowances per NEC Table 314.16(B).
NEC Code Reference
Quick reference guide for NEC 314.16 electrical box fill requirements and code sections.
Volume Converter
Convert between cubic inches and cubic centimeters for electrical box volume calculations.
Conduit Fill Calculator
Calculate conduit fill percentage per NEC Chapter 9. Supports EMT, IMC, RMC, and PVC conduit.
拉線盒尺寸與盒填充指南
區分 NEC 314.16 盒填充體積與 NEC 314.28 拉線盒長度、轉角拉線和 U 形拉線尺寸規則。
Voltage Drop and Box Fill Guide
Plan long branch circuits without missing NEC 314.16 box volume, conductor upsizing, device yokes, clamps, and grounding allowances.
Equipment Grounding Conductor Box Fill Guide
NEC 314.16(B)(5) examples for counting ground wires, bonding jumpers, pigtails, and mixed-size grounding conductors in boxes.
突波保護器盒填充指南
用 NEC 314.16、NEC 242、接地、導線長度、內部夾具和 IEC 突波保護背景選擇 SPD 接線盒。
GFCI Receptacle Box Fill Guide
NEC 314.16 examples for GFCI outlet boxes with line/load conductors, device yokes, pigtails, grounds, and clamps.
USB-C 插座盒填充指南
尺寸 USB-C、USB-A 和組合插座盒，帶有 NEC 314.16 設備軛、接地、夾子和導體計數範例。
端子台線盒容積指南
端子台、導線數量、接地容積、夾具與實際線盒尺寸的 NEC 2023 範例。
多線分支電路盒填充指南
共用中性線分支電路進入接線盒、開關盒或插座盒時，用本指南依 NEC 314.16 檢查盒容量。
Dishwasher and Disposal Box Fill Guide
NEC 314.16 examples for dishwasher junction boxes, disposal switch boxes, GFCI receptacles, grounds, clamps, and 12 AWG kitchen wiring.
Smart Switch Box Fill Guide
Worked NEC box-fill examples for smart switches, neutral bundles, travelers, pigtails, and deep electronic controls.
馬達隔離盒填充指南
規格馬達斷開、泵浦控制和馬達接線盒，配有 NEC 314.16、NEC 430、接地、夾子和 IEC 外殼空間檢查。
電動車充電器盒填充指南
Worked box-fill examples for NEMA 14-50 outlets, hardwired EVSE wallboxes, 40 A and 60 A charging circuits, and outdoor charger junctions.
導線連接器盒填充指南
導線螺帽、扳桿連接器、接線束、尾線與實際盒容量的 NEC 314.16 範例
Frequency Table Calculator
Quick electrical frequency table for 50 Hz, 60 Hz, generator output, VFD output, and field compatibility checks.
Box Fill Chart
Quick chart for common electrical box sizes, conductor-only capacity, and practical box choices before you run the exact NEC calculation.
Box Fill Calculator PDF
Download a printable NEC 314.16 worksheet PDF for field counts, rough-in notes, and final box-volume checks.
吊扇盒填充指南
NEC 314.16 和 NEC 314.27 下的风扇额定吊顶盒、支撑配件和导体数量的工作示例。
浴室風扇和燈箱填充指南
尺寸浴室風扇、燈、定時器、濕度控制和加熱器開關盒，帶 NEC 314.16 導線數。
鋁線盒填充指南
用於鋁分支電路、插座維修、饋線接頭和 NEC 110.14 / 314.16 檢查的盒裝範例。
防風雨盒填充指南
適用於室外 GFCI 插座、防風雨開關、幫浦電路和潮濕位置接線盒的盒裝範例。
延長環和延長盒填充指南
列出的延長環、延長盒、泥環的工作範例，以及何時更大的盒子是唯一安全的答案。
中性線和尾線盒填充指南
中性線、共用中性線、尾線、智慧開關和多聯設備盒的 NEC 314.16 計算範例。
多位開關盒填充指南
2 位元和 3 位元開關盒、調光器、智慧開關和擁擠的改造佈局的工作盒填充範例。
迷你分離式斷開指南
針對小型分離式斷開相鄰盒、鞭形過渡件和大型 HVAC 導線的盒子填充和外殼尺寸建議。
發電機入口指南
針對便攜式發電機入口盒、傳輸相鄰接頭和較大備用電源導體的盒填充和外殼尺寸建議。
熱水器指南
針對儲水式熱水器、無水箱電路、斷開相鄰盒子和較大分支電路導體的盒子填充和外殼尺寸建議。
太陽能斷開盒填充指南
針對光伏交流斷路器、快速關閉接頭、逆變器轉換和大型太陽能饋線導體的工作盒填充範例。
Essential Electrical Calculation Tools
Our suite of free electrical tools helps electricians, contractors, and engineers perform accurate calculations for NEC compliance.
Why Use Our Electrical Tools?
- NEC NEC Compliant: All calculations follow current National Electrical Code requirements
- Always Free: No registration, no subscriptions, no hidden fees
- Mobile Friendly: Use on any device, perfect for on-site calculations
- Regularly Updated: Updated for NEC 2023 including terminal block requirements