Before you worry about voltage drop or wire gauge, you need to know how many amps each run is really pulling. Here’s the quickest two-step routine, one calculation before you install, one measurement after everything is live.

Pencil-and-paper estimate (design phase).

 List every fixture on the home-run and add their wattage's or VA ratings. Divide that total by the voltage you expect the lamps to be at. Most designers will use 12V as a conservative baseline; if you know the circuit starts on a 15 V tap, use 15V instead. Example: Six 5W path lights plus four 7W spot lights = 58W. Divide 58W by 12V and you get roughly 4.8 A. That number guides your wire-size choice and voltage-drop math, and confirms the transformer tap can handle the load.

Volt / Clamp-meter reality check.

Once the system is energized, grab a true RMS clamp meter that reads down to a tenth of an amp. Clamp around one conductor, either the hot or the common, not both—or the reading will cancel out. Let the LEDs stabilize for thirty seconds, then read the current while every lamp is burning. Repeat for each home-run cable and jot the results on the transformer door for future reference.

Finishing the Job

Expect the measured current to land within about ten percent of your calculation, but trust the clamp meter if there’s a mismatch, driver tolerances, lamp aging, and last-minute fixture swaps can all shift the load. If the real amperage is higher than you planned, rerun your voltage-drop math with the new number and fix the wiring before you close your trench. That’s all it takes: one quick calculation, one field measurement, and you’ll know your amperage cold on every landscape-lighting line.