SettingsSettings for this calculationUS
The straight-line distance the lights will span, end to end.
For a patio perimeter, measure around the space; for a criss-cross pattern, add up each individual run.
The spacing between bulbs on your specific string light product.
Common consumer string lights space bulbs every 12 in (1 ft); some styles space them farther apart.
String light length needed
53.9 linear ft of string lights
Sag allowance varies with how tightly the lights are strung — a straighter, more taut installation needs less allowance than a deliberately draped, scalloped look.
- Bulb count
- 54 bulbs
- Whole bulb spacings round the run
- 53
- Left over at the last bulb
- 0.9 ft
They open the calculator with your figures already in it
Outdoor String Light Calculator: 53.9 linear ft of string lights — shown in imperial, US market. The link sets both, so the result they see is the one on your screen.
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How this was calculated
Formula source(s)
- String lights drape with some sag between mounting points, adding roughly 10% beyond a straight-line perimeter measurement
Inputs used
- Total Run Length
- 49 ft
- Bulb Spacing
- 12 in
Intermediate steps
- Bulb count
- 54 bulbs
- Whole bulb spacings round the run
- 53
- Left over at the last bulb
- 0.9 ft
Confidence note: Sag allowance varies with how tightly the lights are strung — a straighter, more taut installation needs less allowance than a deliberately draped, scalloped look.
What this calculation does not cover
- This is a length and lamp-count take-off, not an electrical calculation. It reports no wattage, no current and no limit on how many strings may be connected end to end — that limit is a condition of the product's listing, it moves with lamp technology, and the first string's cord and plug fuse carry everything downstream of them. Circuit capacity, GFCI protection and a wet-location receptacle cover are separate decisions this result does not inform.
- The sag allowance is a fixed 10% on whatever run length you enter, not a figure derived from the drape you actually plan. Extra length over a straight span grows roughly with the square of the sag, so a visually taut run needs a small fraction of that allowance and a deep scalloped drape between widely spaced posts needs more.
- Only the span you type is counted. The drop from the last mounting point to the receptacle, service loops left at each post for re-tensioning, and any vertical rise up to the mounting height are not in the answer — add them to the run length yourself or the order comes up short at the power end.
- The length is continuous and the lamp count is simply that length divided by your bulb pitch. Real strings come in fixed strand lengths with a fixed socket count and unlit lead and tail cord at each end, so the number of strands you buy — and the lamps that come with them — will step around this figure rather than match it. No spare lamps or breakage allowance is included.
- Nothing here covers what carries the load: the catenary wire, turnbuckles, S-hooks or ties, and the posts that take the horizontal pull. Tension climbs as sag falls, so the tidier look doubles or worse the force at both ends, and the string's own conductors must never be the tension member.
Estimated cost — your price
This site holds no price list for this material — local prices vary too much to publish honestly. Enter your supplier's price and the result is costed with it.
Computed in your browser — nothing you enter is uploaded. Presented in US customary units and US trade terminology. Where a formula follows a published standard, that standard and its edition are cited beside it on this page; where none governs, the page says so. Local amendments override model codes — verify against the code in force where you build.
Sources checked 2026-09-02 · in the site-wide review of 2026-09-06 · v1.1.1
Regulatory standards & verification citations1
- String lights drape with some sag between mounting points, adding roughly 10% beyond a straight-line perimeter measurement
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