C9 wire length
Convert socket count and spacing into the socket-wire feet you need for a C9 (or C7) run, plus optional lead and spare.
wire_ft = (sockets − 1) × (spacing_in ÷ 12) + lead_ft + spare_ft · (or sockets × spacing for spool planning)
When to use
This tool helps when you want a c9 wire length planning figure with the assumptions written down. You will enter number of sockets / bulbs, socket spacing (inches), lead / drop to power (feet), and spare / corner waste (feet).
Convert socket count and spacing into the socket-wire feet you need for a C9 (or C7) run, plus optional lead and spare. Keep units consistent (feet vs inches, watts vs amps), then use the formula box to see how each term contributes.
Stop and ask a licensed electrician when loads, hardwired outlets, or roof work go beyond temporary plug-in holiday displays.
Common C9 stringers: 12" or 15".
Worked example
Example inputs from the form defaults — Number of sockets / bulbs = 50; Socket spacing (inches) = 12; Lead / drop to power (feet) = 6; Spare / corner waste (feet) = 5 — are plausible homeowner figures, not a survey of your roofline.
Compute with: wire_ft = (sockets − 1) × (spacing_in ÷ 12) + lead_ft + spare_ft · (or sockets × spacing for spool planning). Show intermediates before the final count or cost.
When the calculator and scratch math disagree, fix units first; the c9 wire length model is only as good as consistent inputs.
Limits / assumptions
Assumptions: inputs match the hints (measured eaves, nameplate watts, package strand length, and so on). Terms not named in the formula are not secretly included.
Limits: outdoor weather, GFCI trips, and real stock sizes vary. Prefer outdoor-rated cords and clips; ladder and roof work need their own safety practices.
Responsibility: confirm safety-critical electrical and height decisions with manuals and, when needed, a qualified professional. PWC Lights does not stamp displays.
FAQ
Span vs spool?
Span is the lit run from first to last socket. Spool mode matches how many feet of pre-spaced cord you buy (sockets × spacing).
Already have linear feet?
Use the C9 / C7 bulb count calculator instead — this page starts from socket count.
C7 too?
Same math if spacing matches your cord.
Voltage drop?
Long single runs can dim; see outdoor cord voltage drop for power feeds.