Christmas Light Calculator

Frequently Asked Questions

How many Christmas lights do I need for a tree?

The standard rule is about 100 lights per vertical foot of tree: a 6 ft tree needs ~600 lights, an 8 ft tree ~800. Go sparse (70/ft) for a minimalist look with visible ornaments, or dense (140/ft) for a full glow. This calculator applies your density choice automatically.

How many lights do I need for a roofline?

Measure the roofline in feet, then divide by your bulb spacing: 6-inch spacing means 2 lights per foot, 12-inch spacing means 1 per foot. An 80 ft roofline at 6-inch spacing needs ~160 lights. Add 10–15% extra for sags, corners, and the drop to the outlet.

How much does it cost to run Christmas lights?

Very little with LEDs. A 100-light LED strand uses about 5–10 watts; running 10 strands 6 hours a day for a month costs roughly $0.50–$1.50 in electricity. Old incandescent strands use ~10× more power — switching to LED is the single biggest saving.

LED vs incandescent Christmas lights — which is better?

LEDs win on almost everything: they use ~90% less electricity, stay cool (much lower fire risk), last 10+ seasons, and come in warm-white and multicolor. Incandescents have a slightly warmer, nostalgic glow that some people prefer — but for rooflines and big displays, LED is the practical choice.

How many strands can I connect end-to-end?

For LED strands, most manufacturers allow 20–25 strands end-to-end (check your box). For incandescent, the limit is usually just 3–5 strands — more than that overloads the wire and trips the breaker. When in doubt, run a second extension cord rather than a longer chain.

Is this Christmas light calculator free?

Yes — completely free, no signup, no downloads. It runs 100% in your browser, so your answers never leave your device.