LED strip light PCB is made of copper, and copper has electrical resistivity. The longer the strip, the more voltage drops at the end — causing uneven brightness. This guide includes real-world voltage drop tests for DC12V vs DC24V strips, long cable scenarios, and practical solutions to keep your lighting consistent.
What Is a Voltage Drop?
Voltage drop is the decrease of electrical potential along the path of a current flowing in a circuit. The longer the LED strip or cable, the more voltage drops occur. When voltage drops below the LED's rated range, brightness decreases and color shifts.
DC12V LED Strip Voltage Drop Test
We measured voltage at 4 points along a 15-meter DC12V LED strip. Each photo shows the actual multimeter reading.
Result: At 15m, voltage dropped from 12.54V to 8.9V — a 29% loss. The strip end is noticeably dimmer. DC12V is best for runs under 5-10m.
DC24V LED Strip Voltage Drop Test
Same 15-meter test, but with DC24V LED strip (6 LEDs/unit instead of 3).
Key insight: Total drop percentage is similar, but DC24V uses 6 LEDs/unit vs 3 for DC12V. This means DC24V has half the voltage drop per LED — far more stable for long runs.
12V vs 24V: Side-by-Side Comparison
Long Cable + LED Strip Voltage Drop Test
Setup: 10m thick cable connected to 15m DC24V LED strip (LT-5050WW60R-W24). We measured voltage at each point along the cable and strip.
Observation: The thick 10m cable barely drops voltage (24.2V → 24.3V). Most loss occurs in the strip itself (17.9V → 16.2V). Use thick cables and power strips from both ends for long installations.
What Causes Voltage Drop?
Input Voltage
Higher voltage = smaller per-LED drop. DC24V halves the drop per LED compared to DC12V.
Wire Gauge
Thicker wires have lower resistance. Use appropriate AWG for your run length.
Wire Length
Longer cables and strips mean more resistance and greater drop.
Strip Wattage
Higher wattage strips draw more current, accelerating voltage drop.
How to Avoid Voltage Drop
Maximum Run Length by Strip Model (DC24V)
12V Wire Gauge & Maximum Distance Chart
Tip: Unaddressed voltage drop can cause LED strip flickering and uneven brightness. Always test voltage at both ends of your run.
Conclusion
Voltage drop is not an unsolvable problem. Understand how it happens, choose the right voltage (DC24V for long runs), use proper wire gauge, and consider parallel wiring or multiple drivers. With these steps, your LED strips will maintain consistent brightness across the entire installation. New to LED strips? Check our beginner's guide.
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About Author
JerryHu
Founder of Lightstec.Engineering degree.More than 13 years working experience in led lighting business.Familiar with producing led lighting products.This blog share you knowledge and solution in led lighting.Welcome sourcing led lights from China.
Learn More Professional Led Classes Which Less People Tell You Before You Make Mistake.
We introduce ourself as a traders in London and trading products in UK as Vesta LED Light and looking for reliable sources of supply for Flexible LED Strip lights.
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1. SMD 3528 12V, 4.8W/m, 60LED/m, warm white & Daylight
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5. SMD 5050 24V, 14.4W/m, 60LED/m, warm white & Daylilght
6. SMD 5050 24V, 14.4W/m, 60LED/m, warm white & Daylilght – IP65
7. SMD 2835 24V, 14.4W/m, 60LED/m, warm white & Daylilght
8. SMD 2835 24V, 14.4W/m, 60LED/m, warm white & Daylilght – IP65
9. SMD 3528 12V, 4.8W/m, 60LED/m, Red, Blue, Green, Yellow, any other colour you have.
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You go to all this trouble to explain Vd but then don’t declare what you feel is a reasonable Vd at the end of a long feed wire?
We frequently use 24V 23W/m LED tape and mount the power supplies and dimming modules remotely – this results in longish cable feeds to the LED Tape.
What percentage or Vd figure do you think is acceptable at the end of the feed wire (i.e the connection to the tape)