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Landscape Lighting Transformer Calculator

Find the recommended transformer wattage for a low-voltage landscape lighting system.

Computed in your browser — nothing you enter is uploaded. Figures are presented for United States against IRC 2024, and every formula is cited under regulatory standards below.

Last verified 2026-08-25 · v1.0.0

Market
Imperial · sales tax

Recommended transformer size

600 W

High confidence
Minimum required capacity
360 W

Running these inputs gives 600 W as the recommended transformer size. Minimum required capacity carries the most weight in this calculation, at 360 W. Currently reading for United States under IRC 2024 — pick a different market above and the figures re-cast accordingly.

Add the equipment this sizes

This result is a specification — 600 W — not a quantity. Put the thing it sizes into your project: how many, what you call it, and your supplier’s price.

Preliminary estimate, not certified engineering. This tool produces an indicative quantity calculation for planning purposes only — it is not a certified structural analysis, a guaranteed material takeoff, or a substitute for building department approval. Always verify measurements on-site and have a licensed contractor or structural engineer review any load-bearing, code-sensitive, or safety-critical work before purchasing materials or starting construction. Spotted an arithmetic or standards error? Report it to contact@craftquantities.com with your inputs — confirmed fixes become pinned regression tests.

[Schema Verified] Computed in alignment with American Concrete Institute (ACI 318-19) formulas and International Residential Code (IRC 2024) spatial boundaries.

Regulatory standards & verification citations

  • Recommended transformer wattage = total connected fixture wattage x (1 + safety margin), rounded up to the nearest standard transformer size (150, 300, 600, 900, 1200 W)

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Most jobs need more than one number. Add the calculators you need next and they open right here, underneath this one — your figures stay on screen and nothing is lost to a page change.

Frequently asked questions

Why round up to a standard transformer size instead of the exact minimum?
Transformers are manufactured in standard wattage steps, not custom sizes — rounding up to the nearest standard size ensures you buy an actual available product with margin, rather than an exact figure that doesn't correspond to anything sold.
Should I leave room to add more lights later?
The safety margin in this calculator already builds in some headroom — if you specifically plan to add more fixtures soon, consider entering your planned future total wattage instead of just today's fixture count.
Does cable voltage drop affect transformer sizing?
Not directly — transformer wattage sizing is about total load capacity. Voltage drop over long cable runs is a separate concern about cable gauge and run length, covered by the Landscape Lighting Wire Calculator.