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Christmas lights calculator

How many feet of Christmas lights you need comes down to two very different measurements: the tree and the roofline. A classic tree wants about 100 mini lights per vertical foot — 700 bulbs on a 7-footer — but the same 700 bulbs is 145 feet of strand at 2.5-inch spacing or 230 feet at 4-inch, so spacing decides what you actually buy. A roofline is pure geometry: straight eave runs plus each gable's two sloped sides, padded 10–15% for corners and the plug run. This calculator handles both, then estimates the total wattage against a standard outdoor outlet, so you know whether one cord carries the whole display or it needs a second one.

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Christmas Lights Calculator

Estimate strand feet, sets to buy, and outlet load for a Christmas tree or a full roofline outline.

Inputs used

Where are you hanging lights?A Christmas tree

Tree height7 ft

How full should it look?Classic — the standard glow

Bulb spacing on the strand4 in — standard mini sets

Length per strand or reel25 ft

Bulb typeLED — low draw, more strands per outlet

Results

Bulbs neededEstimate700 bulbs

From the classic rule of about 100 lights per vertical foot; sparse or fuller shifts that.

Lit length neededEstimate233.3 ft

Strands to buyEstimate10 strands

Rounded up — one spare strand is never wasted at clipping-up height.

Estimated total drawEstimate58 W

From typical per-foot wattage; the label on your sets is the real number.

Power planAbout 58W total — LED sets draw roughly 6W per 25-ft strand, so one standard outdoor outlet carries this with room to spare. Check each set's label for its own end-to-end connection limit.

Additional notes

Where are you hanging lights?

Tree height

Floor to tip of the tree, not to the star.How full should it look?

Bulb spacing on the strand

Usually on the box: strand length divided by light count.Length per strand or reel

On the box — 25 ft is a typical 100-count mini set.Bulb type

Your estimate

Results

Planning estimate

Bulbs needed^EST.700 bulbs

From the classic rule of about 100 lights per vertical foot; sparse or fuller shifts that.

Lit length needed^EST.233.3 ft

Strands to buy^EST.10 strands

Rounded up — one spare strand is never wasted at clipping-up height.

Estimated total draw^EST.58 W

From typical per-foot wattage; the label on your sets is the real number.

Partner pick

The math, plainly

How it works

01
Tree mode starts from the classic rule of thumb — about 100 mini lights per vertical foot for the standard look, from 50 for sparse branches to 200 for a full wall of light — then converts bulbs to feet of strand using the bulb spacing printed on the box.
02
Roofline mode adds up your straight edges and computes each gable's two sloped sides from width and rise with basic geometry, then pads the total by 10–20% for corners, plug ends, and the run back to the outlet.
03
Both modes estimate total wattage from typical per-foot draw (LED minis ~0.25 W/ft, incandescent minis ~1.6, LED C9 ~1, incandescent C9 ~7) against the roughly 1,440W planning limit of a standard 15-amp circuit, so you know how many outlets the display needs.

Try a real scenario

A 7 ft tree and a two-gable roofline

InputsTree: 7 ft, classic, 4-inch spacing. Roofline: 120 ft of eaves, two 24-ft gables with 8-ft rise, 15% extra. 25-ft strands.

ResultTree: about 700 bulbs ≈ 233 ft of strand — 10 strands. Roofline: about 204 ft — 9 strands. In LED that draws roughly 200W on one outlet; in incandescent C9s it's ~1,430W, split across two.

Questions, answered

FAQ

How many feet of lights for a 7-foot tree?

A classic 7-foot tree wants about 700 mini lights — roughly 100 per vertical foot. In strand feet that's about 145 ft at 2.5-inch spacing, 230 ft at 4-inch, or 350 ft at 6-inch, which is why two people with the same tree buy different amounts. Match your strand's spacing and the calculator does the rest.

How many strings of Christmas lights can I connect end to end?

Follow the limit printed on the set — the plugs, wiring, and fuse are rated for it. As a planning figure, a standard 15-amp circuit carries about 1,440W for sustained loads: 40W incandescent sets use that up quickly, while LED sets barely register. Count what else shares the circuit, too.

LED or incandescent Christmas lights?

LED draws a fraction of the power, runs cooler, and lets one outlet carry far more strands; incandescent gives the traditional warm glow but adds real wattage fast. For a whole roofline, LED usually pays for itself in fewer cords, clips, and outlets.

How do I measure my roofline for lights?

Walk the edges you'll light with a tape, or measure along the ground and add the overhang. For a gable, measure the base width and the peak height — each sloped side is the square root of half-the-width squared plus the rise squared. Add 10–15% for corners and the run back to the outlet.

Christmas lights calculator

Enter your details

Christmas Lights Calculator

Inputs used

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Additional notes

Results

How it works

A 7 ft tree and a two-gable roofline

More options for this calculator

LED mini string lights (paid link)

C9 LED roofline strands (paid link)

Light clips (paid link)

Christmas lights calculator

Enter your details

Inputs used

Results

Additional notes

Results

How it works

A 7 ft tree and a two-gable roofline

More options for this calculator

LED mini string lights (paid link)

C9 LED roofline strands (paid link)

Light clips (paid link)

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