String lights calculator for patios, yards and tents
Enter the space and the pattern to see how many feet of café lights and how many strands to buy. A typical strand is 48 ft with a bulb every 2 to 3 ft.
Enter your measurements
More options: Sag · Strand · Bulbs …
- Length of lights
- 118 ft
- Bulbs (plus about 5% spare, at least 2)
- 76 bulbs
- Separate runs from the outlet
- 1 run
- Extension cord to the outlet
- 15 ft
zigzag: 40 ft ÷ 8 ft crossings × √(20 ft² + 8 ft²) = 108 ft + 10% = 118 ft
118 ft ÷ 48 ft strands = 3 strands
- Use lights and cords rated for outdoor use, plugged into a GFCI-protected outlet, and keep connections off the ground and out of puddles.
- Lights across open space need support: a guide wire (a steel cable kit) takes the weight so the cord is not doing it, and poles or a sturdy anchor at each end.
Quick answers for common sizes
| Example | Answer |
|---|---|
| How many string lights for a 20x40 tent | 3 strands of 48 ft (zigzag every 8 ft) |
Strands by pattern for this space
| Pattern | Strands to buy | Length of lights | Bulbs (plus about 5% spare, at least 2) |
|---|---|---|---|
| perimeter | 3 strands | 132 ft | 76 bulbs |
| zigzag | 3 strands | 118 ft | 76 bulbs |
| parallel runs | 4 strands | 176 ft | 101 bulbs |
| center spokes | 4 strands | 164 ft | 101 bulbs |
Café or bistro string lights are sold by the strand — 48 ft is a common length — with a bulb every 2 to 3 ft. Enbrighten’s lights space bulbs 24 in apart (24 bulbs on 48 ft); Brightech’s 48 ft strand has 15 sockets 3 ft apart. How many strands you need depends on the pattern far more than on the size of the space.
How the length is worked out
perimeter = 2 × (length + width) zigzag ≈ (length ÷ spacing) × √(width² + spacing²) parallel = (length ÷ spacing + 1) × width + length strands = length of lights × (1 + sag) ÷ strand length
| Space | Perimeter | Zigzag, 8 ft spacing | Parallel runs, 8 ft spacing |
|---|---|---|---|
| 10 × 12 ft | 2 strands | 1 strands | 1 strands |
| 12 × 16 ft | 2 strands | 1 strands | 2 strands |
| 20 × 20 ft | 2 strands | 2 strands | 2 strands |
| 20 × 30 ft | 3 strands | 2 strands | 3 strands |
| 20 × 40 ft | 3 strands | 3 strands | 4 strands |
| 30 × 40 ft | 4 strands | 4 strands | 6 strands |
Worked example
How many string lights for a 20x40 tent — zigzag, parallel and perimeter compared.
Hanging tips
- Outdoor-rated only. Enbrighten’s FAQ is blunt: only outdoor-rated lights are safe outside. Plug into a GFCI outlet.
- Check the linking limit. It is printed on the box; Enbrighten allows up to 750 ft, but many strands allow much less.
- Use a guide wire for spans across open space, and clip the lights to it.
- Plan the plug end. Start the first strand at the outlet so the cord does not cross a walkway.
- Timer. An outdoor plug-in timer turns them on at dusk.
For a Christmas tree instead, see the Christmas tree lights calculator — for example how many lights for a 6 ft tree or how many lights for a 9 ft tree.
What you’ll need
- Outdoor string lights (48 ft)Mid-range price
Café-style bulbs on a heavy cord for patios and tents. Check the maximum number of strands that can be connected on the label.
See options on Amazon (opens in a new tab) - Outdoor extension cordBudget price
Rated for outdoor use, long enough to reach the outlet without joining several cords. Plug outdoor lights into a GFCI-protected outlet.
See options on Amazon (opens in a new tab) - Outdoor plug-in timerBudget price
Turns tree and patio lights on at dusk and off at bedtime, so nobody leaves them on all night.
See options on Amazon (opens in a new tab)
As an Amazon Associate we earn from qualifying purchases. Links to products are affiliate links — they cost you nothing extra and help keep these calculators free.
Frequently asked questions
How many string lights do I need for a patio?
Measure the patio and pick a pattern. Around the edge of a 12 × 16 ft patio is about 62 ft of lights with sag — two 48 ft strands. A zigzag across it every 8 ft takes only about 32 ft; closer spacing takes more.
How far apart are the bulbs on string lights?
It depends on the product: Enbrighten’s café lights are 24 in apart; Brightech’s 48 ft strand has sockets 3 ft apart. Check the box.
How many strands of string lights can I connect?
Whatever the box says. Enbrighten allows up to 750 ft of its café lights end to end; other brands allow far less. Above that, run a separate cord from another outlet.
How much extra should I allow for sag?
About 10% for a gentle swag. Tight runs on a guide wire need less; deep swags between poles need more.
Sources
- Enbrighten (Jasco) — Café lights FAQ (opens in a new tab) — 24 in between bulbs, an 18 in lead from the plug to the first bulb and a 6 in lead-out; 48 ft strands with 24 bulbs; up to 750 ft can be linked; only outdoor-rated lights are safe outside.
- Brightech — Ambience Pro LED string lights, 48 ft (opens in a new tab) — 24 ft (7 sockets) or 48 ft (15 sockets), sockets 3 ft apart; S14 2 W LED bulbs.