Wire Size Calculator
Calculate the minimum wire size needed for your electrical application
Calculate Required Wire Size
Standard: 3% for most applications
Wire Sizing Guide
Why Wire Size Matters
Choosing the correct wire size is critical for safety, efficiency, and equipment performance. Undersized wire can cause excessive voltage drop, overheating, fire hazards, and equipment damage. Oversized wire wastes money and space but provides a safety margin.
Wire Sizing Formula
Where:
- ρ = Resistivity of copper = 0.0172 Ω·mm²/m (at 20°C)
- I = Current in Amperes (A)
- L = One-way cable length in meters (m)
- ΔV = Maximum allowed voltage drop in Volts (V)
- 2 = Factor for round trip (positive and negative conductors)
Key Sizing Factors
1. Voltage Drop
Wire must be large enough to keep voltage drop within acceptable limits (typically ≤3%).
2. Current Capacity (Ampacity)
Wire must handle the current without overheating. This calculator focuses on voltage drop; always verify ampacity separately.
3. Temperature Rating
Higher ambient temperatures reduce current capacity. Derating may be required.
4. Installation Method
Conduit, free air, or bundled cables have different ampacity ratings.
Common Applications & Wire Sizes
| Application | Current | Typical AWG | mm² |
|---|---|---|---|
| LED lighting | 1-5 A | 18-16 | 0.82-1.31 |
| 12V automotive | 10-20 A | 14-12 | 2.08-3.31 |
| Industrial control | 5-15 A | 16-14 | 1.31-2.08 |
| Power tools | 15-20 A | 14-12 | 2.08-3.31 |
Important Safety Notes
⚠️ Warning:
This calculator provides wire size recommendations based on voltage drop only. Always verify that the wire meets ampacity (current capacity) requirements and complies with local electrical codes.
- Always use wire rated for your voltage and application
- Check local electrical codes and regulations
- Consider derating factors (temperature, bundling, etc.)
- Use appropriate insulation type for environment
- When in doubt, consult a licensed electrician
Custom Wire Harness Engineering
Let our experts design and manufacture your wire harness with optimal wire sizing.