Step 1: measure every run
Measure each roofline section separately: front eave, garage eave, each rake of each gable, ridges, and any dormers. A measuring wheel on the ground under each eave is quicker than climbing, and for rakes you can measure the horizontal distance and add about 10 to 20 percent for the slope. Write down each section as its own run, and note where the nearest outlet is.
Step 2: convert feet to sockets
Multiply feet by 12 to get inches, then divide by the spacing in inches. At 12 inch spacing, sockets equal feet. At 15 inch spacing, sockets are feet times 0.8. At 24 inch spacing, sockets are feet times 0.5. Round each run up.
Step 3: add spares and round to packs
Add about five percent to the bulb count for spares, and buy them in the same order and color so they match. Then round up to whole packs or cases. Clips follow the socket count; plugs follow the run count.
A worked example
A house with 180 feet of roofline across 4 runs, lit with C9 LED bulbs at 15 inch spacing:
| Item | Math | Quantity | Listed cost |
|---|---|---|---|
| Sockets | 180 ft x 12 / 15 | 144 | - |
| Spare bulbs | About 5 percent | 8 | - |
| C9 LED bulbs, 25 pack | (144 + 8) / 25, rounded up | 7 packs | $139.65 |
| C9 O clips, 100 pack | One per socket plus spares | 2 packs | $49.90 |
| C9 socket wire, 15 in, 1,000 ft | 180 ft used, rest kept for later | 1 spool | $240.00 |
| Male plugs, 50 pack | One per run (4) plus spares | 1 pack | $37.99 |
| Photocell timer | One per outlet used | 1 | $11.00 |
Total at listed prices: $478.54, with 820 feet of wire left on the spool for next year or another building. If the runs chain together, add a female plug pack at $37.99.
Buying a whole 1,000 foot spool for a 180 foot house is the main cost in this example. If you only need one house worth of wire, compare it against a prebuilt kit such as the 250 ft kit with 12 in spacing at $435.00, which bundles 250 feet of wire, bulbs, clips, stakes and plugs.
Quick reference: bulbs by roofline length
| Roofline | 12 in spacing | 15 in spacing | 24 in spacing |
|---|---|---|---|
| 50 ft | 50 | 40 | 25 |
| 100 ft | 100 | 80 | 50 |
| 150 ft | 150 | 120 | 75 |
| 200 ft | 200 | 160 | 100 |
| 300 ft | 300 | 240 | 150 |
| 500 ft | 500 | 400 | 250 |
These are socket counts before spares. For large jobs, compare the per-bulb price of 25 packs ($0.80) against the 500 case ($0.64): above roughly 16 packs, the case costs less than buying packs.
Mini lights for trees and shrubs
For tree trunks, the strand length needed is roughly the trunk circumference times the number of wraps: measure the height, decide how far apart each spiral should be (a few inches for a solid band), divide height by that gap for the number of wraps, then multiply by the circumference. Add the same for each major limb you wrap. For shrubs, measure the width and height of the face you will cover and drape strands side to side. Single mini strands are $15.00 and a case of 24 is $299.00.
Turn the count into an order. The shopping list gathers every part with its current price. Order it from Christmas Light Supplier: ships every order free, the same day it is placed, with no order minimum and no added fees.