Cable Section Calculator – Electrical Wire Sizing
Calculate minimum cable section for electrical installations
How to Use
- Enter the current (amperes) your cable will carry
- Enter the system voltage (volts)
- Enter the cable length (meters)
- Set the power factor (typically 0.8-1.0)
- Set the maximum voltage drop percentage (typically 3-5%)
- Select the phase type (single or three-phase)
- Select the installation type (conduit, open air, or buried)
- Click calculate to see the minimum cable section needed
What is Cable Section?
Cable section, also known as wire gauge or cross-sectional area, refers to the thickness of an electrical conductor measured in square millimeters (mm²). The correct cable section is crucial for safe and efficient electrical installations.
Choosing the right cable section ensures that the wire can safely carry the required current without overheating or causing excessive voltage drop.
Factors Affecting Cable Size
- Current Load: Higher currents require larger cable sections
- Cable Length: Longer cables need larger sections to minimize voltage drop
- Voltage Drop: Maximum allowable voltage drop affects minimum cable size
- Installation Method: Cables in conduits require larger sections due to heat buildup
- Ambient Temperature: Higher temperatures reduce current-carrying capacity
- Cable Grouping: Multiple cables together require derating
- Power Factor: Affects the actual power transmitted
Understanding Voltage Drop
Voltage drop is the reduction in voltage as electrical current flows through a conductor. Excessive voltage drop can cause equipment malfunction, reduced efficiency, and overheating.
Common maximum voltage drop limits:
- Lighting circuits: 3%
- Power circuits: 5%
- Combined (distribution + final circuit): 5-8%
Installation Types
| Installation Type | Characteristics | Derating Factor |
|---|---|---|
| In Conduit | Reduced heat dissipation, most common in buildings | 0.8 |
| Open Air | Best heat dissipation, outdoor installations | 1.0 |
| Buried | Poor heat dissipation, underground installations | 0.7 |
Standard Cable Sizes (mm²)
Common standard cable sizes: 1.5, 2.5, 4, 6, 10, 16, 25, 35, 50, 70, 95, 120, 150, 185, 240, 300 mm²
Always select the next standard size up from your calculated minimum to ensure safety and compliance with electrical codes.
Frequently Asked Questions
- What is the difference between cable section and wire gauge?
- Cable section (mm²) is used in metric systems and represents the actual cross-sectional area. Wire gauge (AWG) is used in imperial systems and is inversely related to size (higher gauge = smaller wire). This calculator uses mm² which is more intuitive.
- Why is voltage drop important in cable selection?
- Excessive voltage drop causes equipment to receive less voltage than designed for, leading to poor performance, overheating, and potential damage. Electrical codes typically limit voltage drop to 3-5% for safety and efficiency.
- Can I use aluminum cables instead of copper?
- Yes, but aluminum cables require approximately 1.6 times the cross-section of copper cables for the same current-carrying capacity due to higher resistivity. This calculator is designed for copper cables.
- What power factor should I use?
- For resistive loads (heaters, incandescent lights), use 1.0. For inductive loads (motors, transformers), use 0.8-0.9. For mixed residential/commercial loads, 0.9 is a typical value.
- Do I need to consider other derating factors?
- Yes, this calculator includes installation type derating. Additional factors to consider include ambient temperature correction, cable grouping, and harmonic currents. Always consult local electrical codes and a qualified electrician for final sizing.