Cable Size Chart and Selection Guide

Time: 2026-01-22 11:33:34 Source: Henan Province Jianyun Cable Co., Ltd.

By Jianyun Cable – Professional Manufacturer of Quality Electrical Cables

1. Introduction: Why Cable Sizing Matters
2. AWG to mm² Conversion Chart
3. Ampacity Table for Copper & Aluminum Cables
4. Voltage Drop Calculation Guide
5. Step-by-Step Cable Size Selection Process
6. Recommended Cable Sizes for Common Applications
7. Key Factors That Affect Cable Sizing
8. Final Checklist & Tips

Choosing the correct electrical cable size is one of the most critical steps in any wiring project. Undersized cables can overheat, cause voltage drop, trip breakers, or even start fires. Oversized cables waste money and material. This comprehensive 2025 guide provides clear cable size charts, ampacity tables, voltage drop calculations, and a step-by-step selection process to help you size cables safely and efficiently for residential, commercial, or industrial applications.

1. Introduction: Why Cable Sizing Matters

Proper cable sizing ensures:

Safe current-carrying capacity (ampacity) without overheating
Acceptable voltage drop (typically ≤3–5%)
Compliance with electrical codes (NEC, IEC, BS 7671, etc.)
Long-term reliability and energy efficiency

2. AWG to mm² Conversion Chart

Most North American projects use AWG; international projects use mm².

AWG Size	Diameter (mm)	Cross-Section Area (mm²)	Typical Use (Copper)
14 AWG	1.63	2.08	Lighting circuits (15 A)
12 AWG	2.05	3.31	General outlets (20 A)
10 AWG	2.59	5.26	Dryers, water heaters (30 A)
8 AWG	3.26	8.37	Subpanels, large appliances (40–50 A)
6 AWG	4.11	13.3	EV chargers, feeders (60 A)
4 AWG	5.19	21.2	Main service entrances (100 A)

3. Ampacity Table for Copper & Aluminum Cables

Based on NEC 2023/2026 (90°C insulation, ambient 30°C, 3 current-carrying conductors in raceway).

AWG / mm²	Copper Ampacity (90°C)	Aluminum Ampacity (90°C)	Typical Breaker Size
14 AWG / 2.08 mm²	25 A	N/A	15 A
12 AWG / 3.31 mm²	30 A	25 A	20 A
10 AWG / 5.26 mm²	40 A	30 A	30 A
8 AWG / 8.37 mm²	55 A	40 A	40–50 A
6 AWG / 13.3 mm²	75 A	55 A	60 A
4 AWG / 21.2 mm²	95 A	75 A	80–100 A

4. Voltage Drop Calculation Guide

Voltage drop should be ≤3% for feeders, ≤5% total (NEC recommendation).

Formula (single-phase): VD = (2 × L × I × R) / 1000

VD = Voltage drop (volts)
L = One-way length (meters)
I = Load current (amps)
R = Resistance per km (Ω/km) from table

Approximate resistance (copper at 75°C):

14 AWG: 10.2 Ω/km
12 AWG: 6.4 Ω/km
10 AWG: 4.0 Ω/km
8 AWG: 2.5 Ω/km
6 AWG: 1.6 Ω/km

5. Step-by-Step Cable Size Selection Process

Determine load current (amps) from appliance ratings or calculations
Choose breaker size (next standard size above load)
Select insulation temperature rating (90°C XLPE preferred)
Check ampacity table – select smallest size ≥ breaker rating
Calculate voltage drop – upsize if >3–5%
Apply derating factors: ambient temperature, bundling, continuous load
Verify local code minimum sizes (e.g., 2.5 mm² sockets)
Consider future expansion & add 20–25% margin

6. Recommended Cable Sizes for Common Applications

Application	Recommended Size (Copper)	Breaker	Notes
Lighting Circuits	1.5 mm² / 14 AWG	10–15 A	Max 10–12 points
General Power Outlets	2.5 mm² / 12 AWG	16–20 A	Kitchen counters, bedrooms
Cooker / Oven	6 mm² / 8–10 AWG	32–40 A	Dedicated circuit
EV Charger (Level 2)	6–10 mm² / 6–4 AWG	32–50 A	Check charger specs
Subpanel Feeder (100 A)	25–35 mm² / 2–1 AWG	100 A	Calculate voltage drop

7. Key Factors That Affect Cable Sizing

Load current (continuous vs non-continuous)
Ambient temperature (derate above 30°C)
Number of current-carrying conductors (derate >3)
Installation method (conduit, tray, direct burial)
Voltage drop over distance
Local code requirements
Future expansion needs

8. Final Checklist & Tips

Always use ampacity tables from your local code
Calculate voltage drop for runs >15–20 m
Derate for heat, bundling, and continuous loads
Choose XLPE (90°C) over PVC (70°C) for higher capacity
Consider copper for critical circuits; aluminum for large feeders
Verify cable markings & certifications
Consult a qualified electrician for complex installations

Proper cable sizing ensures safe, efficient, and long-lasting electrical systems. Use this guide as a reference and always comply with local electrical codes.

Need high-quality electrical cables in all standard sizes – copper, aluminum, XLPE, PVC, armored – with full compliance and technical support? Contact Henan Province Jianyun Cable Co., Ltd. for reliable solutions tailored to your project.