Start With the Route, Not the Patio Size
The number that matters is the length of wire you'll actually need overhead, not the footprint of the patio itself. A 12-by-16-foot patio can need very different amounts of string light depending on whether you're running one line along an edge, one line across the middle, or a full crisscross pattern over the whole space.
Measure each planned run separately: house-to-post, post-to-post, or however your layout breaks down, and add them together. If you're doing a zigzag or crisscross pattern (the most common look for full patio coverage), expect the total wire length needed to run noticeably higher than the patio's straight-line dimensions — as a rough estimate, plan for about 1.5 times the straight-line distance to account for the extra length used crossing back and forth.
Factor In Bulb Spacing
Check the spacing listed for the specific set you're considering — it varies by style. G40 bulb sets commonly space bulbs every 12 inches, giving a dense, even glow. Edison/S14 sets are often spaced farther apart, since the bulbs themselves are larger and more visually prominent, so a similar total length will show fewer, more spaced-out bulbs. If you want a denser look, either choose a closer-spaced G40 set or plan for more total runs across the space.
Account for Connectable Runs and Max Wattage
Many string light sets are designed to connect end-to-end, but nearly every manufacturer caps how many sets can be safely linked together on one circuit before it exceeds the circuit's rated wattage. Check the specific set's listed maximum connectable length or bulb count before assuming you can just keep plugging strings together — exceeding that limit is a real overload risk, not just a technicality.
If your total planned run exceeds one set's maximum connectable length, you'll need either a second set powered from a separate outlet/circuit, or a commercial-grade set designed for longer continuous runs (these are common on restaurant and cafe patios for exactly this reason).
A Simple Way to Estimate
When in Doubt, Round Up
It's generally easier to have a little extra length you don't fully use (or save for a future run) than to hang a layout and discover you're a few feet short of your last anchor point. If you're between two set-length options, sizing up slightly is the safer call, especially since connecting a second full set can sometimes exceed a circuit's rated wattage — checking your total length needs upfront avoids both problems at once.
