Solid vs Stranded Wire

Wire comes in two basic constructions: solid (a single conductor) and stranded (multiple thin wires twisted together). Both have the same AWG size designation but different physical properties and ideal uses.

Solid Wire

A single solid conductor of the full cross-sectional area.

Best For:

In-wall residential wiring (Romex/NM-B)
Push-in terminal connections
Breadboard prototyping
Conduit runs with few bends
Outdoor direct burial

Properties:

Slightly lower DC resistance
Stiffer, holds shape when bent
More prone to fatigue if repeatedly flexed
Cheaper to manufacture
Available in smaller gauges (typically 10 AWG and smaller)

Stranded Wire

Multiple thin wire strands twisted together to form the conductor.

Best For:

Flexible cords and cables
Automotive and marine wiring
Appliance connections
Panel wiring in switchboards
Any application with movement or vibration

Properties:

Highly flexible, won't break from bending
Better for high-frequency (less skin effect)
Larger outer diameter for same gauge
Required for larger gauges (8 AWG and up)
Needs crimped or soldered terminations

Quick Comparison

Property	Solid	Stranded
Flexibility	Low — stiff	High — very flexible
DC Resistance	Slightly lower	Slightly higher
Skin Effect	More pronounced at high freq	Less — better for AC/RF
Fatigue Resistance	Low — will break if flexed	High — designed for movement
Outer Diameter	Smaller	Larger (same gauge)
Cost	Lower	Higher
Termination	Push-in, screw terminals	Crimp, solder, or ferrule
NEC Residential	Standard (14-10 AWG)	Required for 8 AWG+

Key Takeaway

For residential in-wall wiring (14, 12, and 10 AWG), solid wire is standard and preferred. For anything that moves, flexes, or is larger than 8 AWG, stranded wire is the right choice. The ampacity rating is the same for both — NEC Table 310.16 applies regardless of whether the conductor is solid or stranded.