Wire Size Calculator
Wire Size Calculator – Find the Right Cable Gauge for Your Circuit
The Wire Size Calculator helps you determine the correct wire or cable gauge for your electrical system based on voltage, current, distance, and allowable voltage drop. Choosing the right wire size is critical to prevent overheating, ensure energy efficiency, and maintain safety standards in electrical installations.
Why Choosing the Right Wire Size Matters
Incorrect wire sizing can lead to voltage loss, power inefficiency, and even fire hazards. A cable that’s too small increases resistance, which generates excess heat. Oversized cables, on the other hand, can raise material costs unnecessarily. This calculator helps balance both performance and efficiency.
Formula Used in Wire Size Calculation
The wire size formula is derived from Ohm’s law and resistivity principles:
A = (2 × L × ρ × I) / Vdrop
- A = Cross-sectional area (mm²)
- L = Cable length (m)
- ρ = Resistivity of material (Copper ≈ 0.0175 Ω·mm²/m)
- I = Current (Amps)
- Vdrop = Allowable voltage drop (Volts)
Example Calculation
Suppose you need to supply a 20A load over 50m using a 230V circuit with a 3% voltage drop limit.
Allowable voltage drop = 230 × 3% = 6.9 V.
A = (2 × 50 × 0.0175 × 20) / 6.9 = 5.07 mm²
This means a 6 mm² cable is recommended for safe operation.
Voltage Drop Considerations
The calculator also takes into account allowable voltage drop — typically 3% for lighting and 5% for power circuits. Higher voltage drop can cause lights to dim and motors to underperform.
Copper vs Aluminum Conductors
- Copper: Lower resistance, higher conductivity, more flexible, but expensive.
- Aluminum: Cheaper, lighter, but less conductive (requires larger cross-section).
Common Applications
- Residential and commercial wiring
- Solar power and battery systems
- EV charging stations
- Industrial motors and control circuits
Wire Size Reference Chart
| Wire Size (mm²) | AWG | Typical Current Capacity (A) |
|---|---|---|
| 1.5 | 15 | 14 |
| 2.5 | 13 | 20 |
| 4 | 11 | 26 |
| 6 | 9 | 32 |
| 10 | 7 | 45 |
| 16 | 5 | 60 |
Internal Links
External Resources
How to Reduce Voltage Drop in Long Circuits
- Use a larger wire size.
- Shorten cable length.
- Use parallel conductors.
- Increase system voltage (if design allows).
FAQ – Frequently Asked Questions
1. What is the maximum allowable voltage drop?
Most standards recommend no more than 3% for lighting and 5% for other circuits.
2. Can I use this calculator for aluminum wire?
Yes, simply adjust the resistivity value to 0.0282 Ω·mm²/m for aluminum.
3. What wire size should I use for a 100A circuit?
Typically 25 mm² or 2 AWG copper wire, but always verify with this calculator.
4. Does wire temperature affect voltage drop?
Yes. Higher temperatures increase resistance, which increases voltage drop.
5. Is AWG the same as mm²?
No. AWG is an American system; mm² is metric. Both can be converted with reference tables.
Conclusion
The Wire Size Calculator is a must-have tool for electrical design. It ensures your system is safe, efficient, and compliant with code requirements. Combine it with the Voltage Drop Calculator and Current Calculator for complete circuit optimization.
Explore more free electrical and engineering tools at MoreThanaCalculators.com.
Common Mistakes When Choosing Wire Size
One of the most frequent mistakes in electrical design is selecting wire size based solely on current capacity while ignoring voltage drop. Even if a wire can handle the load, it may still cause excessive voltage loss, leading to dim lights or unstable motor operation. This is especially important in long-distance or outdoor installations like garden lighting and solar panels.
Another mistake is using incorrect wire material or insulation type. Copper and aluminum have different conductivity levels, and the choice of insulation (PVC, XLPE, or rubber) affects both current-carrying capacity and thermal resistance. Always check wire specifications to ensure they meet your application’s temperature and voltage requirements.
How to Use the Wire Size Calculator Effectively
- Enter system voltage, current, cable length, and voltage drop limit accurately.
- Use resistance values based on the conductor material.
- Round up to the next standard wire size to ensure safety and compliance.
- Cross-reference your results with Voltage Drop Calculator for maximum accuracy.
Professional Tip
For installations over 100 meters or high-current systems (like electric vehicle chargers, industrial motors, or HVAC units), use multi-strand cables with low resistance. These cables not only reduce voltage drop but also improve flexibility and heat dissipation.
Final Thoughts
The Wire Size Calculator is designed to simplify electrical planning for both beginners and professionals. It helps avoid power loss, ensures safe wiring, and supports energy-efficient designs. Whether you’re wiring a small home circuit or a complex solar system, using the right wire size guarantees reliability and compliance with standards such as NEC and IEC.
Continue exploring related tools like the Voltage Drop Calculator, Current Calculator, and Resistance Calculator to optimize your entire electrical network. For additional reading, visit Electronics Tutorials – Conductors and Voltage Drop.