Footage to spools
C9 socket wire spool calculator
Plan bulk C9 socket wire the way it is sold: 1,000 ft. spools, cut into runs. Enter your roofline and the number of separate runs; get wire length, spools, leftover wire and plugs.
How the spool math works
Wire needed = lit feet × (1 + waste %) + runs × slack. Spools = wire needed ÷ 1,000, rounded up. The lit portion determines the socket count (feet × 12 ÷ spacing), while the slack is the unlit lead at the start of each run.
Runs, not just feet
A house is rarely one continuous line. Garages, porches and separate gables each become their own run with their own plug. Four runs on a 240 ft. roofline need four male plugs and, if they connect end to end, four female plugs. More runs also means more slack wire, which is why the run count matters to the spool total.
Spool pricing at the snapshot date
| Spool | Sockets | Price | Per ft. |
|---|---|---|---|
| 1,000 ft., 12 in. spacing | 1,000 | $275.00 | $0.28 |
| 1,000 ft., 15 in. spacing | 800 | $240.00 | $0.24 |
| 1,000 ft., 24 in. spacing | 500 | $289.00 | $0.29 |
Jumpers and extension cord
Where two runs are separated by a gap, such as a valley or a chimney, installers often bridge it with plain wire instead of unlit sockets. SPT-1 lamp cord comes on 250 ft. spools and is rated 8 amps / 960 watts per the product listing; add plugs to each end to make a jumper of any length. Use the circuit calculator to check how many bulbs one feed can carry.
Frequently asked questions
How many sockets are on a 1,000 ft. C9 spool?
1,000 ft. × 12 ÷ spacing: 1,000 sockets at 12 in., 800 at 15 in., and 500 at 24 in.
How much extra wire should I plan for?
Each run needs a little lead wire to reach the outlet or the next run, plus some waste where you cut between sockets. The calculator adds a per-run slack length and a percentage allowance, both of which you can change.
How many plugs do I need?
One male plug per run at the power end. Add a female plug at the far end of any run that another run or a jumper will plug into. The calculator counts one of each per run.
Can I cut a spool into several runs?
Yes. That is the main reason to buy bulk socket wire: cut each run to the exact length of the roof edge, attach plugs, and keep the rest of the spool for the next job.