The length of LED strip a single power supply can run is limited by two independent factors: the total wattage of the PSU (which you can't exceed) and voltage drop along the strip's copper traces (which limits the length of one continuous run fed from a single point, regardless of how powerful the PSU itself is). In practice, the second factor is usually the deciding one at 12V: even a powerful 150–200W supply won't let you run a single unbroken length of 10–15 m without noticeable dimming at the far end — you'll need to split the strip into several runs with power injection points. In this guide, the ARTLED team explains both limits, gives you the calculation formulas, and provides ready-made tables for 12V, 24V, and 48V systems.
Two independent limits you need to account for
✓ The power supply's wattage limit. The total power draw of all connected strip (W/m × length) must not exceed the PSU's rated output with a 20–30% safety margin — this is a matter of safety and the PSU's own lifespan.
✓ The voltage drop limit. The copper traces on an LED strip have their own resistance — the longer the run fed from a single point, the more the voltage sags at the far end, regardless of how much headroom is left on the power supply. For a detailed breakdown of the mechanism, see our article on voltage drop in LED strips.
The wattage limit: formula and table
The maximum length by wattage is calculated as:
where PPSU is the power supply's rated wattage (W), Pm is the strip's power draw per meter (W/m), and 0.8 is the 20% safety margin factor (the minimum recommended; for continuous long-term operation, 25–30% is safer).
| PSU wattage | 9.6 W/m strip (60 LEDs/m) | 14.4 W/m strip (120 LEDs/m) | 19.2 W/m strip (240 LEDs/m) |
|---|---|---|---|
| 60 W | 5.0 m | 3.3 m | 2.5 m |
| 100 W | 8.3 m | 5.5 m | 4.2 m |
| 150 W | 12.5 m | 8.3 m | 6.25 m |
| 200 W | 16.6 m | 11.0 m | 8.3 m |
| 300 W | 25.0 m | 16.6 m | 12.5 m |
This figure shows how many meters the PSU can feed in total — but it doesn't tell you whether that length can be run as a single unbroken piece without power injection points.
The voltage drop limit: table for 12V/24V/48V
Approximate maximum length of a single run fed from one point, for a mid-power strip (9.6–14.4 W/m), regardless of how much wattage headroom the PSU has:
| Voltage | No noticeable drop | 15–20% drop |
|---|---|---|
| 12V | up to 5 m | 5–10 m |
| 24V | up to 10 m | 10–20 m |
| 48V | up to 20 m | 20–40 m |
Which limit kicks in first in practice
Comparing the two tables reveals a pattern: on 12V, the voltage drop limit (≈5 m) kicks in before the wattage limit, starting from a 100W PSU and up — meaning that choosing a 150W or 200W unit instead of a 100W one won't let you run a longer unbroken strip; it will only give you extra wattage headroom that needs to be used through separate runs or power injection points. On 24V and 48V, the picture is more balanced: the voltage drop limit (10 m and 20 m respectively) nearly matches what a 150–200W PSU delivers, so higher voltage lets you put a single power supply's full wattage to use in one continuous run.
Practical example. A 150W, 12V PSU with a 14.4 W/m strip: by wattage it can power up to 8.3 m, but without power injection the real limit of a single run is about 5 m. The fix — either feed the 8 m run from both ends at once (each half then only "sees" 4 m), or split the 150W across two separate 5 m runs through a junction box, or move to a 24V system right away, where the same PSU comfortably covers 8–10 m in one continuous run.
How to connect several runs to one power supply
✓ Through a junction box. Power runs from the PSU output through a cable of the right gauge to a junction box, then out to each strip run on its own wire — each run stays within its own voltage drop limit.
✓ Parallel connection of runs. Several strip runs can be wired in parallel to one PSU — the only requirement is that their combined power draw stays within the PSU's rated output plus a 20–30% margin.
✓ Power injection points on a long perimeter. If you need one visually continuous run longer than the voltage drop limit, a separate feed wire from the same PSU is tapped in every 5 m (12V) or 10 m (24V) — the strip's own traces no longer carry the entire load alone.
✓ Feeding from both ends. The simplest way to double a run's practical length without a junction box is to connect both ends of the strip to the PSU — each half then drops half as much.
Common mistakes
The most common mistake is buying a more powerful PSU expecting that alone to let you run a longer unbroken strip, while forgetting about the voltage drop limit. Other frequent errors: feeding 8–10 m of 12V strip from one PSU from a single end with no power injection, sizing the PSU with no 20–30% margin, using thin feed cable (under 0.75 mm²) to a junction box more than 3 m from the PSU, and not planning for a 24V or 48V system upfront when designing long perimeters (stairs, ceiling coves, facades).
Frequently asked questions
Can I connect 10 m of 12V strip to a single powerful PSU without issues?
By wattage alone — yes, if the PSU is rated high enough (for example, 150W for a 14.4 W/m strip). But without power injection points or feeding from both ends, the far end of a 10 m run will be noticeably dimmer due to voltage drop.
What limits the length more — PSU wattage or voltage drop?
At 12V, the voltage drop limit (roughly 5 m per run) usually kicks in before the PSU's wattage limit. At 24V and 48V, the two limits tend to converge, so higher voltage lets you make better use of a supply's full power.
How many runs can I connect to one PSU?
As many as the PSU's total wattage allows with a 20–30% margin — each individual run still needs to stay within its own voltage drop limit, independent of the others.
Can several runs be connected to one PSU through a junction box?
Yes, this is the standard approach for projects with multiple lighting zones (a kitchen and a hallway, for example) — the key is accounting for the combined power draw of all runs and sizing the feed cables accordingly.
Conclusion
The length of LED strip one power supply can run is set by two independent limits: the PSU's total wattage and voltage drop along the strip's traces. At 12V, the second factor usually caps a single continuous run at around 5 m regardless of the PSU's rated power — to put a more powerful supply's full wattage to use, split the strip into several runs, add power injection points, or move to a 24V or 48V system.
ARTLED offers power supplies in a range of wattages, 12V/24V/48V strips with reinforced copper traces, and cable for power injection points. The ARTLED team will calculate the optimal power scheme and number of connection points for your project's length and wattage free of charge.
