LED Tape Max Run Before the Far End Dims
The longest single end-fed run before the far end dims past your drop tolerance.
Example
You enter
- Strip power (W/ft) 4.4
- Supply voltage (V, 12 / 24) 12
- Round-trip resistance (ohm/ft) 0.05
- Acceptable end drop (%) 10
You get
- Max single end-fed run 11.4 ft
No published worked example is on file for this calculation. It is checked against a hand-worked derivation of its method and an independent reference test.
Details, formula, and sources
Scopelen_max = voltage x sqrt(2 x (tolerance/100) / (power_per_ft x resistance_per_ft)). A 4.4 W/ft 12 V strip at 0.05 ohm/ft walls out at about 11.4 ft for a 10% drop; a 24 V strip reaches roughly double (the run scales with the voltage). Answers 'how far can I run this tape' instead of checking one length. Oversizing the PSU does not extend it -- power-inject or feed both ends. The strip datasheet governs.
Formula or tablelen_max = voltage x sqrt(2 x (tolerance/100) / (power_per_ft x resistance_per_ft)); the inverse of led-tape-run's drop_pct = power_per_ft x resistance_per_ft x length^2 / (2 x voltage^2) x 100.
Source and editionConstant-voltage LED strip voltage drop solved for the run length, by name.
Free accessStandard low-voltage LED-strip loading relation; the strip datasheet governs.
What governsEstimate. AHJ and licensed professional govern.
API field namespower_per_ft_w, supply_voltage_v, resistance_per_ft, drop_tolerance_pct, max_run_ft
- Uniform-load drop end-fed uniform load drops half the full-current voltage, so drop scales with length^2 and the max run with the voltageconstant-voltage LED loading
- Round-trip resistance resistance_per_ft must be positive; a zero-resistance strip has no far-end drop to bound the runstrip datasheet