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LED Strip Power Supply Calculator

Size the power supply (in watts) needed for an LED strip lighting run, with a safety margin.

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
16.4 ft
Schematic, drawn to the proportions you entered — not to scale on screen.

Recommended power supply size

47.24 W (recommended supply rating)

Check your inputs

Always confirm against your specific strip's datasheet watts/ft rating — this varies significantly between products.

Raw strip load
39.37 W

At the values currently entered, the recommended power supply size works out to 47.2 W (recommended supply rating). Note that total strip length sits at the low end of the range this calculator was checked against, so treat the output as indicative rather than settled. Confidence is moderate: the method is sound, but real materials and site conditions vary. Figures are shown for United States, where IRC 2024 is the governing residential reference; switch the market above if you are building elsewhere.

Add the equipment this sizes

This result is a specification — 47.244 W (recommended supply rating) — 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

  • Total load = strip length x watts per foot (from the strip's spec sheet); a safety margin keeps the power supply from running at its rated maximum continuously

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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

Can I just add up the strip's rated wattage without a margin?
You could, but running an LED driver continuously at 100% of its rating shortens its lifespan and leaves no room to add more strip later — hence the recommended margin.
Does voltage (12V vs 24V) affect the power supply size in watts?
No — wattage is wattage regardless of voltage. Voltage does affect maximum run length before voltage drop dims the far end of the strip, and affects the current (amps) the supply and wiring must handle.
Can one power supply run multiple separate strip runs?
Yes, as long as the combined wattage of all runs (with margin) stays under the supply's rated output — add up each run's watts per foot x length before applying the margin.