Calculate Wire Size, Voltage Drop & Compliance for Electrical Installations
💡 Sizing based on voltage drop and current capacity. Recommended cable sizes from 1.0mm² to 120mm².
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 (IEC 60364, NEC, BS 7671)
Selection: The calculator selects the smallest standard cable size that meets both requirements
📊 Cable Size Reference Table (Copper)
mm²
AWG
Current (A)
Ω/km
Typical Use
1.0
17
11
17.2
Lighting, small loads
1.5
15
15
11.5
Lighting, sockets
2.5
13
20
6.9
Power sockets, small AC
4.0
11
27
4.3
AC units, ovens
6.0
9
35
2.9
Large AC, water heaters
10
7
50
1.7
Sub-mains, large loads
16
5
70
1.1
Main feeders
25
3
95
0.69
Main switchboard
35
1
120
0.49
Industrial supplies
50
0
150
0.34
Heavy industrial
📌 Standards & Compliance
Standard
Max Voltage Drop
Derating Factors
NEC (USA)
3% Branch, 5% Total
Ambient temp, bundling
BS 7671 (UK/India)
3% Lighting, 5% Power
Grouping, thermal
IEC 60364
3% Lighting, 5% Power
Installation method
💡 Cable Sizing Tips
Always oversize slightly - for future expansion and safety margin
Consider ambient temperature - high temps reduce cable capacity
Bundling effect - multiple cables together reduce capacity
Use copper for critical circuits - better conductivity and reliability
Check local regulations - different countries have specific requirements
❓ Frequently Asked Questions (FAQ)
❓ 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 based on your specific parameters.
❓ What is the formula for cable sizing? ▼
Voltage drop method: VD = (2 × I × L × R) / 1000 (single phase) or VD = (√3 × I × L × R) / 1000 (three phase). The calculator also checks current capacity.
❓ What size cable for 50 amps? ▼
For 50A, typical cable sizes: 10mm² (copper) or 16mm² (aluminum), depending on length and voltage drop. Use this calculator for exact sizing.
❓ Copper vs Aluminum cable - which is better? ▼
Copper has better conductivity (about 60% of aluminum's resistance). Aluminum is lighter and cheaper but requires larger sizes for the same current.
❓ What is the voltage drop formula? ▼
VD = (2 × I × L × R) / 1000 for single phase, and VD = (√3 × I × L × R) / 1000 for three phase. VD is voltage drop in volts.
❓ How to convert AWG to mm²? ▼
AWG to mm² conversion: 10 AWG = 5.26mm², 12 AWG = 3.31mm², 14 AWG = 2.08mm². Use online conversion tools or this calculator's reference table.