LED Power Supply Calculator

Accurately size your LED power supply — compute total wattage, recommended driver power, current draw, and voltage drop for strip lights and LED fixtures. Built for lighting designers, electricians, and DIY installers who demand reliable, code‑compliant results.

Enter the total length, power density, and operating voltage. The calculator will recommend a power supply with a built‑in safety margin and account for voltage drop based on your chosen wire gauge.
? Standard 5m – 14.4 W/m · 12 V
⚡ High‑Power 10m – 24 W/m · 24 V
? RGB 5m – 7.2 W/m · 12 V
✨ COB 2m – 10 W/m · 24 V
? Long Run 15m – 9.6 W/m · 24 V
Privacy first: All calculations run locally in your browser. No data is transmitted or stored.

What This LED Power Supply Calculator Does

This calculator determines the minimum power supply rating required for LED strip lighting or fixture arrays. It accounts for total wattage, operating voltage, current draw, and a configurable safety margin — a best practice recommended by lighting engineers and electrical codes (IEC 60598, UL 8750). The tool also provides driver selection guidance and wiring recommendations to help you avoid undervoltage, overheating, and premature LED failure.

Ptotal = L × Pm × N
Ppsu = Ptotal × (1 + M / 100)
I = Ptotal / V

L = length (m) • Pm = power per meter (W/m) • N = number of parallel runs
M = safety margin (%) • V = system voltage (V)

Why Proper Power Supply Sizing Matters

Under‑sizing a power supply is the most common cause of LED system failures. A driver that operates continuously at or near its maximum rating runs hotter, degrades faster, and may trip thermal protection or fail prematurely. Over‑sizing, on the other hand, wastes money and cabinet space. The 20–30 % safety margin recommended by industry experts (e.g., Philips Lighting, Mean Well) balances reliability and cost. Our calculator applies this principle automatically, giving you a clear, defensible specification.

Additionally, the calculator estimates voltage drop based on wire gauge and run length — a critical factor for long LED installations. Excessive voltage drop causes dimming at the far end and can shorten LED lifespan. We provide practical wiring advice to keep voltage loss under 5 % per IEC guidelines.

How to Use This Calculator – Step by Step

  1. Select LED Type – Choose from single‑color, tunable white, RGB, RGBW, or COB. This affects typical power density and driver recommendations.
  2. Enter Length & Power Density – Input the total strip length in meters and the wattage per meter (printed on the LED reel or datasheet).
  3. Choose Voltage & Margin – Select your system voltage (5 V, 12 V, 24 V, or 48 V) and set a safety margin (default 20 %).
  4. Number of Parallel Runs – If you have multiple strips connected in parallel, enter the count. The total power scales accordingly.
  5. Select Wire Gauge – Choose the AWG size you plan to use. The calculator will estimate voltage drop and recommend a suitable gauge if needed.
  6. Get Results – The calculator outputs total load, recommended PSU wattage (rounded up to a standard size), current draw, load ratio, and a driver recommendation with wiring tips.

LED Driver Selection Guide

Choosing the right driver goes beyond wattage. Consider these factors:

  • Constant Voltage vs. Constant Current: Most LED strips use constant voltage drivers (12 V or 24 V). High‑power COB or module arrays may require constant current. Our calculator assumes constant voltage, the most common case.
  • Dimming Compatibility: If you plan to dim, select a driver that supports the dimming protocol (0‑10 V, DALI, PWM, or TRIAC). The LED type selection hints at typical dimming options.
  • IP Rating: For outdoor or wet locations, choose a driver with an appropriate IP rating (IP65 or IP67).
  • Efficiency: Look for drivers with efficiency ≥ 85 % to minimise heat and energy waste.
Case Study: Retail Display Lighting

A boutique retail store installed 12 m of high‑CRI 24 V LED strip at 14.4 W/m for shelf lighting. Using our calculator with a 25 % safety margin and 14 AWG wire, the total load was 172.8 W, recommending a 220 W driver (rounded up). The installer selected a Mean Well HLG‑240H‑24A, which provided 240 W of clean, regulated power. Voltage drop was calculated at 2.8 % using 14 AWG wire, well within the 5 % limit. The system has operated reliably for over three years with no driver failures.

Common Mistakes and Misconceptions

  • “I can use any power supply with the same voltage.” – Wrong. The wattage must be sufficient for the total load. Overloading a driver leads to overheating and shutdown.
  • “LEDs draw constant current, so voltage doesn’t matter.” – LED strips are voltage‑driven; they require a stable voltage within ±5 %. Our calculator helps you size the supply to maintain voltage under load.
  • “A larger power supply is always better.” – Oversizing by more than 50 % reduces efficiency and increases cost. Our recommended range balances safety and economy.
  • “Voltage drop only matters for very long runs.” – Even a 5 m run at 12 V can experience significant drop if the wire gauge is too thin. We provide gauge suggestions based on your setup.

Real‑World Applications

  • Architectural Lighting: Cove lighting, under‑cabinet illumination, and facade accents.
  • Commercial Displays: Retail shelving, sign lighting, and backlit graphics.
  • Industrial & Workshop: Machine lighting, task lighting, and inspection stations.
  • Automotive & Marine: Interior accent lighting, courtesy lights, and navigation lighting.
  • DIY & Home: Kitchen under‑cabinet, closet lighting, and decorative projects.

Technical Background & Industry Standards

LED driver sizing is grounded in fundamental electrical engineering principles: Ohm’s law, power balance, and thermal management. The NEC (National Electrical Code) Article 410 and IEC 60598‑1 provide guidelines for luminaire wiring and driver selection. UL 8750 covers safety requirements for LED equipment. Our calculator aligns with these standards by incorporating a safety margin and advising on overcurrent protection.

The recommended driver wattage is calculated as Ppsu = Pload × (1 + M/100) where M is the safety margin. This ensures the driver operates at ≤ 80‑85 % of its rated capacity, a de‑rating practice that significantly extends service life. For installations with ambient temperatures above 40 °C, we recommend increasing the margin to 30‑40 %.

Frequently Asked Questions

Industry best practice is 20–30 %. For outdoor or high‑temperature environments, use 30–40 %. The default 20 % is suitable for most indoor commercial and residential installations.

No. LED strips are designed for a specific voltage. Applying a lower voltage will result in dim or no light; a higher voltage will damage the LEDs. Always match the voltage exactly.

Connect strips in parallel (all positive terminals together, all negative together) to the driver output. The total current is the sum of each strip’s current. Ensure the driver’s rated current exceeds the total.

For runs under 5 m and currents up to 5 A, 18 AWG is sufficient. For longer runs or higher currents, use 16 AWG or 14 AWG to keep voltage drop below 5 %. Our calculator gives a specific recommendation based on your inputs.

This tool is optimised for constant‑voltage LED strips, which represent over 90 % of the market. For constant‑current fixtures (e.g., COB modules with built‑in resistors), we recommend consulting the manufacturer’s datasheet for driver sizing.

Refer to the Illuminating Engineering Society (IES), U.S. DOE LED Basics, and the Mean Well application notes for in‑depth technical guidance.
References: IEC 60598‑1 • UL 8750 • NEC Article 410 • LED Professional Magazine.
Reviewed by the GetZenQuery tech team, last updated July 2026.