Lighting tools
LED Voltage Drop Calculator
Drag the lengths. Compare wire sizes. See how much voltage reaches your LED strip.
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Your setup
At 24 V · PSU rating based on 80% loading.
Compare wire sizes
Lower drop means more voltage reaches the strip.
Complete your setup to compare wires.
Check the highlighted inputs. Results will update automatically.
1 mm²
Smallest size within target
2.32%
Voltage drop
23.44 V
At strip input
Select a wire to save or share.
| Wire size | Voltage drop | At strip input |
|---|---|---|
16.6%3.985 V | 20.02 VAbove target | |
9.3%2.231 V | 21.77 VAbove target | |
6.84%1.641 V | 22.36 VAbove target | |
4.65%1.116 V | 22.88 VAbove target | |
3.1%0.744 V | 23.26 VAbove target | |
2.32%0.558 V | 23.44 VWithin target | |
1.55%0.372 V | 23.63 VWithin target | |
0.93%0.223 V | 23.78 VWithin target | |
0.58%0.139 V | 23.86 VWithin target | |
0.39%0.093 V | 23.91 VWithin target | |
0.23%0.056 V | 23.94 VWithin target | |
0.15%0.035 V | 23.97 VWithin target | |
0.09%0.022 V | 23.98 VWithin target | |
0.07%0.016 V | 23.98 VWithin target |
“Exceeds supply” means the nominal-current estimate uses up the supply voltage. Actual current will change, so no strip input voltage is shown.
Copper DC supply cable only. Excludes losses inside the LED strip, connectors and controller. Check cable current rating separately.
Good to know
Which wire size should I choose?
Start with the size marked Minimum : it is the smallest listed copper conductor that meets your voltage-drop target. A larger conductor reduces the drop further.
Then check the cable's current rating, terminal capacity and installation requirements. Meeting the voltage-drop target alone does not confirm a cable is suitable.
Is cable length one-way or round-trip?
Enter the distance from the power supply to the LED strip, measured along the cable route. For a 5 m cable, enter 5 m. The calculator includes the outgoing and return conductors automatically.
Strip length is a separate input. It sets the load; it is not added to the supply cable length.
Will this tell me if the end of my strip is dim?
The result is the voltage at the start of the strip . A long LED strip can lose additional voltage through its own copper PCB.
Follow the strip's maximum run length and feed instructions. Separate feeds or power injection may be needed; calculate each supply cable using the load it carries.
What if the voltage drop is too high?
Try a larger copper conductor, shorten the cable route or split the load into separate feeds. Each feed needs its own calculation.
A higher system voltage reduces cable drop for the same rated load, but only change voltage if the strip, power supply and controller all support it. Do not raise the supply above the strip's rated voltage.
How is the power supply rating calculated?
Strip length × rated power gives the LED load. Divide that load by 0.8 to keep it at or below 80% of the power supply's rating. For example, a 72 W strip needs at least 90 W at the strip's specified voltage.
Choose a suitable available rating and account for other loads, power-supply derating and the manufacturer's requirements.
Calculation method and assumptions
This is a nominal-current estimate for one two-conductor copper DC feed.
R = 2 × ρ(T) × L ÷ A
Voltage drop = I × R
Copper resistivity at 20°C: 0.01724 Ω·mm²/m. Temperature coefficient: 0.00393/°C. AWG areas use the standard geometric formula; mm² and AWG are separate size catalogs.
Actual current depends on the strip and its input voltage. This tool does not calculate AC wiring, copper-clad aluminum, multi-channel cable losses, ampacity, fuse size or brightness.
Can I type a length instead of dragging?
Yes. Use the number field for an exact length. The slider and field control the same value, and the comparison updates immediately. Typing a longer run expands the slider's range.
Click or tap a wire to keep it selected while changing the lengths. Use Use minimum to switch back to the smallest size that meets your target.
Do these sizes mean the cable's diameter?
mm² is the copper conductor's cross-sectional area , not the cable's outside diameter. AWG is a separate gauge system: a lower AWG number means a larger conductor.
The lists use available nominal conductor sizes. A nearby AWG and mm² size are not exact equivalents. Smaller sizes may suit light loads and short connections; always check the cable's current rating and installation suitability.
Keep the calculator with your project.
Use Save results → Download offline copy to keep your inputs and comparison in one file. It works without an internet connection.