A Comprehensive Guide to LED Strip Installation: Calculating Voltage Drop and Cable Sizing

Modified on Tue, 26 Sep 2023 at 03:58 PM

When installing LED strip lighting, understanding the importance of voltage drop and the role of cable size can have a significant effect on the performance of your setup. Voltage drop, a typical electrical occurrence, can influence the brightness and uniformity of your lighting. If not properly managed, it can even lead to potential damage to your LED strips, particularly in lengthy installations.

Understanding Voltage Drop

Voltage drop refers to the reduction in electrical voltage experienced as electricity travels along a wire. Although it's a standard phenomenon in all electrical circuits, it's particularly pertinent when installing extensive LED strips.

Calculating Voltage Drop

The formula for calculating voltage drop is as follows:

Voltage Drop (Vd) = (2 * Length of Cable (L) * Electrical Resistance (R) * Current (I)) / Cross-sectional Area of the Wire (S)


Vd is the Voltage drop

L is the Length of the cable in metres

R is the Electrical resistance of the cable in Ohms per metre

I is the Current in Amps

S is the Cross-sectional Area of the Wire in mm²

To illustrate this, let's consider a 300W/24V load, located 20 metres away from the PSU, utilising a 4.0mm diameter copper cable. Plugging these values into the formula, we get:

Voltage Drop = (2 * 20m * 0.0175 Ohms/m * 12.5A) / 4mm² = 2.19 Volts

So, if we provide 24 Volts from the PSU, the LED strips will operate at approximately 21.81 Volts, factoring in the 2.19V drop.

Cable Size and Distance from LED Driver

Cable selection and its distance from the LED driver are pivotal for managing voltage drop. Larger diameter cables exhibit less resistance and, thus, less voltage drop. Likewise, placing the LED driver closer to the strip reduces voltage drop.

Calculating the Correct Cable Size

The required cable core cross-sectional area (mm²) for each installation can be determined through the following steps:

Calculating the Power Consumption of the LED Strip

Power Consumption (W) = Length of LED Strip (m) x LED Strip Power per Metre (W/m)

Establishing the Current (I) of the Installation

Current (I) = Power Consumption (P) / Voltage (V)

Determining the Cross-Sectional Area of the Cables

Cross-Sectional Area (S) = 2 * Length of Cable (m) * Current (A) / (56 * 0.05 * Voltage (V))

Let's consider a cable length of 4 metres with a current of 3 Amps and a 24 Volt system. Using these values, we get a cross-sectional area of roughly 0.36 mm². Cables come in standard sizes, so you'd select a cable with a cross-sectional area rounded up to the nearest standard size available in the market.

Dimming LED Strips - A Common Misconception

Many people wonder, "Why when I dim my LED strips using a high-quality LED controller are they not damaged?" The answer lies in how dimming is accomplished - not by altering voltage but through a PWM (Pulse Width Modulation) LED controller. This controller maintains the requisite voltage, controlling brightness by changing the duty cycle, thus safeguarding LEDs from under-voltage damage.

Online DC Voltage Drop Calculators

Online DC voltage drop calculators can be handy, providing quick estimates for your installation needs. However, proceed with caution. Not all calculators provide accurate results, so cross-verifying the information is essential.

Testing and Adjusting After Installation

Post-installation, it's recommended to use a multimeter to measure the voltage at both the start and end of your LED strip. If there's a significant voltage drop, consider using a thicker cable, repositioning your LED driver closer to the strip, or installing an additional power supply.


Understanding voltage drop and making informed decisions about cable size can ensure consistent, effective lighting with your LED strip installations. However, this guide serves as a general recommendation. Always refer to specific product documentation and local regulations, or consult with a certified electrician before any installation.

In summary, setting up LED strip lighting might seem like a daunting task, but with the right knowledge about voltage drop and cable sizing, it becomes more approachable. Proper installation ensures a long-lasting, efficient, and bright LED strip light setup that can elevate the aesthetics of any space.

Disclaimer: The calculations provided in this article are intended as a guide. They are approximations and are not guaranteed to be accurate for all systems. Always consult a qualified electrician or other appropriate professional to ensure safety and functionality.

Note: For more comprehensive information on installing LED strips, you can download our detailed PDF guide here: LED Strips Installation Guide. This guide offers additional insights and best practices for a successful installation.

Please note that while this guide is intended to assist you, it's crucial to consult with a qualified installer for the specific requirements and safety considerations of your project. Hi-Line Lighting is not responsible for any issues arising from the installation process.

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