A 100 ft kit is enough only when the route you intend to light, plus a planning allowance, fits within its usable length. House frontage alone does not answer that question. Count the sloping edges of any gable, porch edges and returns you actually want to light.
These are calculated examples, not measurements of customers’ houses. Start with the roofline measuring guide and record your own dimensions on the printable worksheet.
Three examples before you order
For a symmetrical gable, both sloping edges together equal its full width multiplied by the pitch factor. A 6/12 roof has a factor of approximately 1.118. Add those edges to the horizontal sections and extras, then multiply by 1.05 for the calculator’s planning allowance. Round the result up to a whole foot.
| Planned layout | Calculation before allowance | With 5% allowance, rounded up |
|---|---|---|
| Straight front, no gable | 60 ft eave + 8 ft porch = 68 ft | 72 ft |
| Front with one gable at 6/12 | 50 ft eave + 24 ft gable × 1.118 + 8 ft porch | 90 ft |
| Longer front with one gable at 6/12 | 70 ft eave + 30 ft gable × 1.118 + 12 ft porch | 122 ft |
The first two examples fit within 100 ft on length alone. The third does not. A kit that is long enough still needs a compatible layout: its segment boundaries, approved extensions and power connection must work for the house.
Lit footage and cable gaps are different
Sketch the route from the controller to the final light. Mark each garage setback, unlit wall and change of roof level. Record those gaps separately from the edges you want illuminated.
An unlit extension may cross a gap without adding lights, but its permitted length and placement depend on the exact system. A general 5% allowance does not establish electrical compatibility or replace a measured cable route. Check the manual before counting an extension as a solution.
What if the kit is too long?
Do not assume you can remove the extra footage. Some models support specified cuts and connectors; others use non-cuttable segments. Read the cutting and extension guide before choosing between a longer kit and a different layout.
Do not plan to conceal a powered coil of spare lights. Resolve unused length using the manufacturer’s permitted segment arrangement, or choose a different kit. Keep the controller and power supply locations on the same sketch.
Make the final length decision
Use the calculator to reproduce the 122 ft example, then enter your measurements. If your gables differ in width or pitch, calculate each separately using the worksheet; the calculator’s repeated-gable input assumes they are the same.
The result is a planning estimate, not an installation specification. Confirm uncertain dimensions and the exact kit’s maximum supported run before ordering. Then compare permanent outdoor lighting kits by both coverage and installation fit, or see our permanent eave light picks by use case, which lists the 100, 150 and 200 ft options side by side.
Price tiers are our own rough budget bands, not live prices. Check the listing for today’s price.
Frequently asked questions
Will a 100 ft kit cover my house?
Only if the route you want lit, plus a planning allowance, fits within its usable length. Frontage alone does not answer it. In the guide’s examples, 72 ft and 90 ft layouts fit within 100 ft on length, while a 122 ft layout does not.
Why is the calculator’s total bigger than my eave measurement?
It adds the sloping edges of any gable and other lit extras, then applies a 5% planning allowance. For a symmetrical gable, both sloping edges equal its full width multiplied by the pitch factor, which is about 1.118 for a 6/12 roof.
Can I cut a kit that is longer than I need?
Do not assume so. Some models support specified cuts and connectors, while others use non-cuttable segments. Do not plan to conceal a powered coil of spare lights either. Use the manufacturer’s permitted segment arrangement or choose a different kit.
Does an extension cable count as lit footage?
No. An unlit extension may cross a gap without adding lights, but its permitted length and placement depend on the exact system. Record gaps separately from the edges you want lit, and check the manual before counting an extension as a solution.