Calculate Wire Size, Voltage Drop & Compliance for Electrical Installations
💡 Sizing based on voltage drop and current capacity.
Cable Sizing Based on: Voltage Drop & Current Capacity
📖 Cable Size Calculator
Selecting the correct cable size is essential for safe and efficient electrical installations. This calculator determines the required wire size based on voltage drop, current capacity, and cable length. It supports both copper and aluminum conductors, single-phase and three-phase systems.
📐 Cable Sizing Methods
Voltage Drop Method: VD = (2 × I × L × R) / 1000 (single phase) or VD = (√3 × I × L × R) / 1000 (three phase)
Current Capacity Method: Based on cable ampacity tables
Selection: The calculator selects the smallest standard cable size that meets both requirements
📊 Cable Size Reference Table
mm²
AWG
Current (A)
Ω/km
1.0
17
11
17.2
1.5
15
15
11.5
2.5
13
20
6.9
4.0
11
27
4.3
6.0
9
35
2.9
10
7
50
1.7
16
5
70
1.1
25
3
95
0.69
35
1
120
0.49
50
0
150
0.34
📌 Standards & Compliance
Standard
Max Drop
NEC (USA)
3% Branch, 5% Total
BS 7671 (UK/India)
3% Lighting, 5% Power
IEC 60364
3% Lighting, 5% Power
💡 Cable Sizing Tips
Always oversize slightly - for future expansion
Consider ambient temperature - high temps reduce capacity
Bundling effect - multiple cables together reduce capacity
Use copper for critical circuits - better conductivity
❓ Frequently Asked Questions
How to choose cable size? ▼
Cable size is determined by current rating, voltage drop, and installation conditions. Use this calculator to get the recommended size.
What is the formula for cable sizing? ▼
VD = (2 × I × L × R) / 1000 (single phase) or VD = (√3 × I × L × R) / 1000 (three phase).
What size cable for 50 amps? ▼
For 50A, typical sizes: 10mm² (copper) or 16mm² (aluminum).
Copper vs Aluminum cable? ▼
Copper has better conductivity. Aluminum is lighter and cheaper.