LED Strip Wire Gauge Chart for 12V and 24V Runs

LED strip wire gauge comes down to three numbers: how far the driver sits from the strip, how much current the run draws, and how much voltage you're willing to lose on the way. Get it right and the strip sees close to its full 24V or 12V at the input. Get it wrong and you can lose several percent before the light even starts, and no driver upgrade will win it back. The charts below give the maximum one-way feed length for 18 through 10 AWG copper at common loads, worked out for a 3% drop.

The Feed Wire Is Its Own Voltage Drop Problem

A strip loses voltage in two places. The first is inside the strip itself. Copper traces on the circuit board carry current along the run, so the far end sees less voltage than the input. That loss is what a strip's published maximum run accounts for, and our article on 12V vs 24V voltage drop covers it in detail.

The second is the feed: the two conductors between the driver's output terminals and the strip's input pads. That loss happens before the strip gets anything, and the strip's maximum run assumes it isn't there. If the feed eats 6% and the strip's own run adds another 3 or 4%, the far end ends up close to 10% low. On a continuous cove or a shelf where two runs meet, you'll see it.

Feeds have also gotten longer. Drivers get moved to mechanical closets, attics and access panels for service and heat reasons, which is good practice, but it can put 30 to 60 ft of wire between the driver and a cabinet run. At 24V and a few amps, that distance matters more than most people expect.

How to Calculate LED Strip Wire Size

The math fits on one line:

Voltage drop (V) = 2 × one-way length (ft) × current (A) × resistance (Ω per 1,000 ft) ÷ 1,000

• One-way length is the distance from driver to strip along the wire's actual route, up the wall and around the beams, not the straight line on the plan.
• The 2 is there because current goes out on the positive conductor and comes back on the negative. A 40 ft feed is 80 ft of copper.
• Current is the connected load in watts divided by the voltage. A 72 W run at 24V draws 3 A.
• Resistance depends on the gauge. For copper at 68°F:

Every two-gauge step (18 to 16, 16 to 14) cuts resistance by about 37%. Going from 18 to 12 AWG cuts it by 75%. Wire in a hot attic runs a little above these room-temperature values, which is one more reason to keep some margin.

Pick a target drop: 3% or 5%

You need a limit to design to. A common target for the feed is 3%:

• at 24V, 3% is 0.72 V;
• at 12V, 3% is 0.36 V.

5% (1.2 V at 24V, 0.6 V at 12V) is a looser limit. It can be acceptable for a short accent run where nobody can compare one end to the other, but it leaves very little room for the strip's own drop. For continuous lines of light, coves, and anywhere two runs butt together, keep the wire at 3% or below.

Notice how much tighter 12V is. Half the voltage means half the allowable drop in volts, and the same wattage draws twice the current. Put together, a 12V feed reaches one quarter of the distance a 24V feed does for the same load on the same wire.

24V LED Strip Wire Gauge Chart

Maximum one-way feed length, copper conductors, 3% drop (0.72 V). Figures are rounded down to the whole foot.

Two patterns are worth remembering. Doubling the load halves the distance. Moving from 18 to 14 AWG gives about 2.5 times the reach. If your load falls between columns, use the next column to the right, or work the formula directly.

The wattage here is the strip load connected to that feed, not the driver's rating. A 96 W driver feeding 60 W of strip carries 2.5 A, not 4 A. If you accept a 5% limit instead of 3%, multiply any figure in the chart by about 1.67: 14 AWG at 96 W goes from 35 ft to 59 ft.

12V LED Strip Wire Gauge Chart

Maximum one-way feed length, copper conductors, 3% drop (0.36 V), rounded down.

Compare the first columns. A 24 W load on 14 AWG reaches 35 ft at 12V and 142 ft at 24V. On new work with feeds longer than about 15 ft, 24V makes every part of the job easier: lighter wire, fewer feeds, more margin. Keep 12V for short runs and retrofits where 12V supplies are already in place.

A Worked Example: Display Shelving 45 ft From the Driver

Say you're lighting 18 ft of display shelving with a 24V strip rated at 4 W/ft. The driver goes in a utility room, and the wire route measures 45 ft one way.

1. Load: 18 ft × 4 W/ft = 72 W.
2. Driver: 72 W ÷ 0.8 = 90 W minimum, so a 96 W driver.
3. Current: 72 W ÷ 24 V = 3 A.
4. Target: 3% of 24V = 0.72 V.
5. Drop at 45 ft and 3 A:

14 AWG passes, barely. 12 AWG gives real margin. Before you pull 45 ft of 12 AWG, though, check the strip's own limit: if its published maximum run is shorter than 18 ft, you'll be feeding it in two pieces anyway, and that changes the wire math in your favor. The maximum run length guide explains where that figure comes from.

Heavier Wire, a Closer Driver or More Feeds

Heavier copper is one of three fixes, and often not the cheapest.

Move the driver closer

Drop scales directly with distance. In the example, putting the driver in an accessible spot 15 ft from the shelving brings 18 AWG down to 0.57 V, or 2.4%. The 120V AC circuit feeding the driver carries a fraction of the current at five times the voltage, so moving the long run to the line-voltage side is usually the better trade. Keep the driver ventilated and reachable; never seal it behind finished drywall.

Split the load into separate feeds

Two 36 W halves draw 1.5 A each. On 16 AWG at 45 ft, each feed drops 0.54 V, or 2.3%. Two pairs of 16 AWG are easier to pull and terminate than one pair of 12 AWG, and each half of the shelving gets its own feed point, which also helps the strip stay inside its maximum run. Feeding a long run at the middle or from both ends works the same way.

Use a strip built for distance

Strips in the LONG RUN collection hold brightness over much longer single-feed runs, which cuts down the number of feeds. They still need a properly sized feed wire. Their advantage is inside the strip, not in the copper between it and the driver.

Class 2 Limits Are a Reason to Split

Most LED drivers used in homes and light commercial work are Class 2 power sources. Class 2 output is limited to 100 VA, so Class 2 drivers top out around 96 to 100 W, and at the 80% loading rule that's roughly 75 to 80 W of strip per output. The payoff is on the low-voltage side: Class 2 circuits can generally be wired with Class 2 methods and cable (NEC Article 725, with Article 411 covering low-voltage lighting systems) instead of the wiring methods required for power circuits.

That limit shapes the layout. The 150 W column in the 24V chart is beyond any single Class 2 output, and the 96 W column is more than one output should carry at 80% loading. Instead of one large supply with one heavy feed, it's usually simpler to split the load across two or more Class 2 drivers or outputs, each with its own feed. You get smaller currents, lighter wire, and one failure no longer darkens the whole job. Confirm the wiring method with your local inspector or a licensed electrician, since requirements vary by jurisdiction and application. The powering LED strips guide covers driver sizing, and you'll find Class 2 and dimmable options under Power & Control.

Choosing and Terminating the Cable

The cable itself

• Solid or stranded. Solid conductors land cleanly in screw and push-in terminals and are common in in-wall cable. Stranded flexes better where the cable moves or bends tightly around millwork. In screw terminals, finish stranded ends with a ferrule. Don't tin them with solder: solder slowly flows under screw pressure and the joint loosens over time.
• In-wall rating. For Class 2 wiring inside walls and ceilings, use cable marked for the purpose, typically CL2 or CL3 (CL3 can be used where CL2 is called for). Plenum spaces need the plenum version, CL2P or CL3P, and vertical shafts the riser version, CL2R or CL3R. Lamp cord and unmarked speaker wire are not in-wall cable; read the print on the jacket.
• Polarity. Use cable with a marked or colored conductor and keep positive on the same color everywhere. Reversed polarity usually just means a dark strip, but on a job with a dozen feeds it costs time.
• Wet and outdoor locations. Use cable and connections rated for the location, and keep splices in enclosures suited to it.

Heavy wire into small strip pads

Strip pads are small, often just a few millimeters wide. You can't land 12 or 14 AWG on them, and squashing a fat conductor onto a pad lifts the copper or bridges to the next pad. Use a transition instead:

1. Run the heavy feed to a junction point close to the strip: a junction box, a terminal block inside the cabinet, or a protected space at the end of the profile.
2. Splice to a short pigtail of lighter wire, 18 or 20 AWG, or to a connector lead sized for the strip's width. Use lever connectors or terminal blocks rated for both wire sizes, and keep the splice accessible.
3. Connect the pigtail to the strip with solder or a matched solderless connector.

A short pigtail costs almost nothing. One foot of 20 AWG carrying 3 A drops about 0.06 V, roughly 0.25% of 24V. Connector leads and splicing hardware are in power accessories.

Common Mistakes

• Measuring the feed on the plan. The real route goes up walls, over ceilings and around framing. It's routinely 30% longer than the straight-line distance. Measure the route, or add a generous allowance.
• Forgetting the factor of 2. One-way length times current times resistance gives half the real drop. Both conductors count.
• Turning up the driver to compensate. If a driver has an output adjustment, don't raise it to make up for a long feed. Every strip on that driver sees the extra voltage, and the one closest to it gets the most.
• Daisy-chaining runs on one feed. When run two is fed through the end of run one, all of run two's current passes through run one's traces. Give each run its own feed back to the driver or to a junction point.
• Using 12V for a long feed on new work. It reaches a quarter of the distance of 24V for the same load. Unless the 12V supply is already there, specify 24V.
• Not measuring. With everything on, check the voltage at the strip input of each run. If it's more than a few percent below the driver's output, fix the feed before the ceiling closes.