Four free tools
Christmas lights calculators for C9 rooflines
Work out how many C9 bulbs a roofline takes, how much bulk socket wire to buy, how many bulbs a circuit can carry, and what the whole job costs in materials. Prices come from a dated catalog snapshot, so every number is a real one.
C9 bulb calculator
Roofline feet and socket spacing in, bulb count and the lowest-cost mix of 25-packs and 500-bulb cases out.
Open calculatorSocket wire calculator
Total footage, number of runs and slack in, feet of wire and the number of 1,000 ft. spools out, with plugs for every run.
Open calculatorCircuit and amp calculator
Bulb wattage and breaker size in, bulbs per 15A or 20A circuit at the 80% continuous-load limit out.
Open calculatorMaterial cost calculator
One form for the whole job: bulbs, spools, clips, plugs, stakes and timers, priced line by line with a cost per foot.
Open calculatorHow the C9 math works
A C9 roofline is a length of socket wire with a bulb in every socket. The number of bulbs is set by two things only: how many feet you are lighting and how far apart the sockets are. Convert feet to inches, divide by the spacing, and round up. A 100 ft. roofline on 12 in. spacing takes 100 bulbs; on 15 in. spacing it takes 80; on 24 in. spacing it takes 50.
Bulk socket wire is sold on 1,000 ft. spools with the sockets already molded in, so the spacing is chosen when you buy the spool. The 15 in. spool carries 800 sockets, the 12 in. spool carries 1,000, and the 24 in. spool carries 500. You cut each run to length and add a male plug at the power end and a female plug at the far end if another run will plug into it.
Choosing a spacing
| Spacing | Bulbs / 100 ft. | Typical look |
|---|---|---|
| 12 in. | 100 | Dense, continuous line; common on shorter rooflines and storefronts |
| 15 in. | 80 | The middle option; reads as a solid line from the street on most houses |
| 24 in. | 50 | Separated points of light; useful on long commercial eaves and fences |
LED vs incandescent wattage
Power is where LED and incandescent C9s part ways. An incandescent C9 bulb draws about 7 watts, so a 15 amp household circuit loaded to 80% (1,440 watts) runs about 205 of them. An LED C9 bulb draws roughly 0.5 to 1 watt, so the same circuit can run well over a thousand. The circuit calculator shows the limit for the wattage printed on your bulbs, and it keeps the 80% continuous-load rule for holiday lighting that stays on for hours each night.
What goes into a material budget
Beyond bulbs and wire, a finished roofline needs a clip for every socket (All in One clips for gutters and shingles, C9 O clips, or magnet clips for metal), plugs for each run, stakes if you line a walkway, and a photocell timer so the lights come on at dusk. The material cost calculator adds all of it and picks packs or cases for each line, whichever costs less for the quantity you need.
Frequently asked questions
Which calculator should I start with?
Start with the C9 bulb calculator if you only need a bulb count. If you are building runs from bulk socket wire, use the socket wire calculator next, then check power with the circuit calculator. The material cost calculator combines all of it into one priced parts list.
How do I measure a roofline for C9 lights?
Measure every edge you plan to light, in feet: eaves (gutter lines), rakes (the sloped gable edges), ridges and any peaks. Add the edges together. A laser measure from the ground works for eaves; for rakes, measure the horizontal width and use the roof pitch, or measure along the edge from a ladder.
Where do the product prices come from?
Prices are a dated snapshot (September 27, 2026) of the Christmas Light Supplier catalog: C9 LED bulbs, bulk socket wire spools, clips, plugs, stakes and photocell timers. Each line in a result links to the product page, which shows the current price.
Are the results exact?
They are planning estimates. Bulb and socket counts follow directly from length and spacing, so they are accurate for the footage you enter. Wire totals include a waste allowance you control, and circuit numbers depend on the bulb wattage you enter, so read the rating on your bulbs and outlets.
Do LED C9 bulbs really use less than 1 watt?
Most LED C9 replacement bulbs draw roughly 0.5 to 1 watt each, compared with about 7 watts for a traditional incandescent C9. The circuit calculator lets you change the wattage so you can match the number printed on your bulbs.