Plan reliable wiring for irrigation, ponds, and sheds. Choose copper or aluminum with drop limits. Export results to share with your installer today easily.
Enter your garden power run details. Choose a voltage-drop limit, and the tool will suggest a minimum conductor size.
Use these sample scenarios to understand typical inputs and outputs for garden wiring runs.
| Scenario | System | Voltage | Load | Length | Drop limit | Material | Typical outcome* |
|---|---|---|---|---|---|---|---|
| Path lights | DC | 12 V | 120 W | 25 m | 3% | Copper | Often 8–10 AWG |
| Pond pump | AC Single-Phase | 230 V | 800 W | 35 m | 5% | Copper | Often 12–10 AWG |
| Greenhouse fan | AC Single-Phase | 120 V | 500 W | 30 m | 3% | Aluminum | Often 8–6 AWG |
The calculator converts your load into a design current and then adds a margin. For example, a 120 W lighting run at 12 V with 85% efficiency draws about 11.76 A; a 10% margin raises it to 12.94 A for sizing. This margin helps cover start-up surges, seasonal upgrades, and minor voltage sag at the source.
Voltage drop is the main limiter on long garden runs. A 3% target is common for low-voltage lighting to protect brightness and driver stability, while 5% is often acceptable for motors and general outlets. At 12 V, 3% equals only 0.36 V, so long distances can require thick conductors. The tool supports either percent or a fixed volt limit for consistent planning.
Copper has lower resistivity than aluminum, so it drops less voltage for the same size. The model starts at 1.724×10⁻⁸ Ω·m for copper and 2.82×10⁻⁸ Ω·m for aluminum at 20°C, then adjusts with temperature coefficients (0.00393 and 0.00403). In warm conduit or sun‑heated trenches, higher temperature increases resistance and drop. Aluminum may still be practical, but it often needs larger sizes and approved terminations with antioxidant compound.
For DC and single‑phase AC, the round‑trip path is approximated as 2× the one‑way length because current flows out and back. For three‑phase loads, the tool uses a √3 length factor for a line‑to‑line drop approximation, which is widely used in field estimates. Enter the one‑way distance; the calculator converts feet to meters using 0.3048 and applies the correct path factor automatically.
The calculator also reports power loss: Ploss = I²R. Losses above roughly 3–5% of load power can create heat and wasted energy, especially in buried conduit. Voltage helps. If no listed size meets both drop and ampacity targets, reduce length, increase voltage, split loads, use multiple runs, or consult a qualified electrician for code-compliant options.
It is the smallest listed conductor size that meets your voltage‑drop limit and an estimated ampacity target at the selected insulation rating, using the design current after your safety margin is applied.
For low‑voltage lighting, 3% helps keep brightness consistent. For motors, pumps, and general circuits, 5% is often used in planning. Always follow any stricter manufacturer or local requirements.
Resistance increases with temperature. A warmer conductor produces more voltage drop and higher losses for the same current and length. Enter a realistic temperature for sun‑exposed conduit or buried cable runs.
Yes. The calculator adjusts resistivity by material and temperature, then checks against different ampacity estimates. Aluminum may require a larger size and properly rated terminations; consult an electrician for connections and protection.
No. Enter the one‑way distance from the source to the load. The calculator applies a round‑trip factor for DC and single‑phase, and a √3 factor for three‑phase line‑to‑line approximations.
Use it for planning and budgeting. Final selection must also consider cable type, burial depth, conduit fill, ambient conditions, overcurrent protection, grounding, and code rules. A qualified electrician should approve the design.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.