Use this free Busbar Size Calculator to determine the correct copper or aluminium busbar size based on current load. Includes formula, example calculation, and downloadable Excel sheet.
What is a Busbar?
A busbar is a metallic strip or bar made of copper or aluminium used to distribute electrical power in:
- Electrical panels
- Switchgear
- Distribution boards
- Busbar trunking systems
Busbars provide high current capacity with low resistance, making them ideal for power distribution.
Busbar Current Capacity Formula
The basic formula used for busbar sizing is:
Current Capacity = Width × Thickness × Current Density
Where:
| Parameter | Description |
|---|---|
| Width | Busbar width (mm) |
| Thickness | Busbar thickness (mm) |
| Current Density | Current per mm² |
Typical Current Density Values
| Material | Current Density |
|---|---|
| Copper Busbar | 1.2 – 1.6 A/mm² |
| Aluminium Busbar | 0.8 – 1.0 A/mm² |
Copper carries more current than aluminium.
Example Busbar Calculation
Suppose we have:
Width = 50 mm
Thickness = 10 mm
Material = Copper
Current Density = 1.5 A/mm²
Step 1: Calculate area
Area = Width × Thickness
Area = 50 × 10
Area = 500 mm²
Step 2: Calculate current capacity
Current = Area × Current Density
Current = 500 × 1.5
Current = 750 A
✅ Busbar current capacity = 750 Amps
Busbar Size Table (Copper)
| Busbar Size | Current Capacity |
|---|---|
| 25 × 3 mm | 112 A |
| 25 × 5 mm | 187 A |
| 40 × 5 mm | 300 A |
| 50 × 6 mm | 450 A |
| 50 × 10 mm | 750 A |
| 75 × 10 mm | 1125 A |
| 100 × 10 mm | 1500 A |
Online Busbar Calculator Logic
Inputs:
Material
Width (mm)
Thickness (mm)
Current Density
Formula:
Area = Width × Thickness
Current Capacity = Area × Current Density
Download Busbar Calculator (Excel)
You can also download the Excel sheet to calculate busbar size automatically.
Download Busbar Size Excel Calculator
