Landscape Lighting Calculator
Calculate transformer size, wire gauge, and voltage drop for landscape lighting. Size your low-voltage lighting system with per-run wire recommendations.
Wire Runs
Wire Gauge Recommendations
| Run | Distance | Est. Fixtures | Amps | Wire Gauge | Voltage Drop |
|---|---|---|---|---|---|
| Run 1 | 50 ft | 5 | 2.1A | 16 AWG | 0.84V (7.0%) |
| Run 2 | 75 ft | 5 | 2.1A | 12 AWG | 0.50V (4.1%) |
How It Works
Enter the number of fixtures, watts per fixture (most LED path lights are 3–7W), and your system voltage (12V is standard for residential landscape lighting).
Add wire runs with their distances. The calculator sizes your transformer at 120% of total load and recommends wire gauge for each run based on amperage and distance.
The voltage drop column shows estimated voltage loss per run. If any run shows more than 10% drop, consider using thicker wire, splitting the run, or moving the transformer closer.
Frequently Asked Questions
What size transformer do I need for landscape lighting?
Add up the total wattage of all fixtures and multiply by 1.2 (20% buffer). Choose the next standard transformer size above that number. For example, 10 fixtures at 5W = 50W x 1.2 = 60W — a 100W transformer is sufficient. Standard sizes are 100, 150, 200, 300, 600, 900, and 1200 watts.
What wire gauge should I use for landscape lighting?
Wire gauge depends on the total amps and run distance. For short runs under 50 feet with low wattage, 16 AWG works. For runs of 50–100 feet, use 14 or 12 AWG. For long runs over 100 feet or high-amperage circuits, 10 AWG keeps voltage drop acceptable. Keep voltage drop under 10% per run.
What is voltage drop and why does it matter?
Voltage drop is the loss of voltage as electricity travels through wire. In a 12V system, even a small drop (1–2 volts) can make lights noticeably dimmer. Keep total voltage drop below 10% (1.2V on a 12V system). Use thicker wire or shorter runs to reduce voltage drop.
How many landscape lights can I put on one run?
This depends on wattage and run distance. A typical 100W transformer can handle about 80W of fixtures (with 20% buffer). With 5W LED fixtures, that is 16 lights. Split them across 2–3 runs to minimize voltage drop and ensure even brightness across all fixtures.