Calculator Inputs
Example Data Table
| Scenario | Voltage | Load Power | Length | Material | Size | Estimated Drop |
|---|---|---|---|---|---|---|
| Cabinet strip lighting | 24 V DC | 96 W | 12 m | Copper | 2.5 mm² | 1.19 V |
| Landscape path lights | 12 V DC | 60 W | 20 m | Copper | 4.0 mm² | 1.17 V |
| Accent lighting branch | 230 V AC | 180 W | 30 m | Aluminum | 2.5 mm² | 0.92 V |
These examples are illustrative. Actual values change with current, temperature, conductor area, power factor, and driver efficiency.
Formula Used
1) Temperature-adjusted resistivity
ρT = ρ20 × [1 + α × (T − 20)]
2) Loop resistance
R = (2 × L × ρT) ÷ A
3) Voltage drop
Vdrop = I × R
4) Percentage voltage drop
% Drop = (Vdrop ÷ Vsupply) × 100
5) Power loss in conductors
Ploss = I² × R
Variable meanings:
- ρ20 = resistivity at 20°C.
- α = temperature coefficient of resistance.
- T = conductor operating temperature in °C.
- L = one-way cable length in meters.
- A = effective conductor area in mm², including parallel runs.
- I = design current after future load margin.
This calculator uses a two-conductor loop model, suitable for most DC and single-phase LED lighting circuits.
How to Use This Calculator
- Select the circuit type for your LED lighting run.
- Enter supply voltage and choose either power-based or current-based input.
- Provide one-way cable length, conductor material, and cable size.
- Add temperature, allowed drop, efficiency, and future load margin.
- Submit the form to view voltage drop, cable loss, and recommended size.
- Use the CSV or PDF buttons to save the result set.
Frequently Asked Questions
1. Why is voltage drop important for LED lighting?
Excessive drop lowers the voltage available at fixtures. That can reduce brightness, shift color performance, create uneven illumination, and stress constant-voltage drivers or long LED strip runs.
2. What voltage drop percentage is usually acceptable?
Many designers aim for 3% on branch lighting circuits. Some installations tolerate 5%, but lower drop generally improves consistency, especially on low-voltage LED systems.
3. Why does the calculator ask for one-way length?
The formula internally doubles the entered length to represent the full loop path. Current leaves on one conductor and returns on the other.
4. Does conductor temperature really matter?
Yes. Resistance rises as conductor temperature increases. Higher resistance raises voltage drop and cable loss, so warm installations can perform worse than room-temperature estimates.
5. Should I enter LED load power or driver input power?
Enter the LED load power when using the efficiency field. The calculator estimates electrical input current by accounting for driver efficiency and, for AC, power factor.
6. What does parallel conductors mean here?
Parallel conductors share the current and increase total effective area. That lowers resistance and voltage drop, assuming conductors are identical and installed correctly.
7. Can I use this for both strips and fixtures?
Yes. It works for many LED circuits, including strips, cabinet lighting, landscape runs, and fixture feeds, provided the circuit behaves like a DC or single-phase loop.
8. Why does the recommended cable size exceed the minimum?
The tool applies a small sizing buffer, then rounds to a common standard area. That helps account for installation variation and keeps design choices practical.