Calculator / How many lights do you need?
Trees, rooflines and shrubs
How many lights do you need?
Before the load question comes the quantity question. These are the rules of thumb that hold up, and how to measure so they do.
Trees
The working figure for a wrapped tree is 100 lights per foot of height for a full look, or 50 per foot for something sparser. A seven foot tree therefore takes around 700 lights — seven 100-light sets — and that is for the tree alone, before anything else on the circuit.
That figure assumes wrapping branches rather than draping. Draping around the outside uses roughly half as many and looks it. For an outdoor tree you are wrapping the trunk and main limbs, so measure the height you will actually reach rather than the height of the tree.
Rooflines
Measure the run in feet or meters and add ten percent for sag and corners. C9 bulbs are typically spaced 12 inches apart and C7 at 6 to 8 inches, so a 40 foot roofline takes 40 C9 bulbs, or 60 to 80 C7 depending on the spacing.
Measure at ground level along the wall rather than guessing from a photograph, and remember that a gable adds two sloping runs longer than the horizontal distance they span. The slope is roughly the horizontal run divided by the cosine of the pitch — or, more usefully, add about 20 percent for a typical roof pitch.
Quantity rules of thumb
| What | Rule | Example |
|---|---|---|
| Wrapped tree, full | 100 lights per foot of height | 7 ft tree → 700 lights |
| Wrapped tree, sparse | 50 lights per foot | 7 ft tree → 350 lights |
| Draped tree | Half of wrapped | 7 ft tree → 350 lights |
| Roofline, C9 | 1 bulb per 12 in | 40 ft → 40 bulbs |
| Roofline, C7 | 1 bulb per 6–8 in | 40 ft → 60–80 bulbs |
| Gable ends | Add ~20% for pitch | 40 ft span → 48 ft of run |
| Shrub, wrapped | 100 lights per 3 ft shrub | 3 shrubs → 300 lights |
| Hedge, netted | One 4×6 ft net per face | Measure visible face only |
Shrubs and hedges
Net lights are sold by coverage area, commonly 4 by 6 feet. Measure the face of the shrub you can actually see and divide. Two nets rarely join invisibly, so plan for one net per shrub where you can.
For wrapping rather than netting, 100 lights covers roughly a 3 foot shrub.
Then check the load
Quantity and load are different questions, and the second one is where displays go wrong. Seven sets on a tree is nothing in LED and most of a chain limit in incandescent. Once you know how many sets you need, put them into the calculator on the front page.
Common questions
How many lights for a 7 foot Christmas tree?
About 700 for a full wrapped look, or 350 for something sparser. The common rule is 100 lights per foot of height.
How many C9 bulbs for a 40 foot roofline?
About 40, since C9 bulbs are usually spaced a foot apart. Add ten percent for sag and corners, and around twenty percent more for any gable run.
How do I measure a roofline for lights?
Measure along the wall at ground level rather than estimating from a photo, then add for the pitch of any gable — a sloping run is longer than the horizontal distance it covers.
How many net lights for a shrub?
One 4 by 6 foot net per shrub face is the usual answer. Joins between nets are hard to hide, so avoid splitting one shrub across two.
Work out your own load
The load calculator checks both limits against your display.