LED Strip Power Supply Calculator
Calculate the correct power supply wattage and wire gauge for your LED strip light installation.
LED strip power calculation is essential for selecting the correct power supply and wiring. An undersized power supply will dim the LEDs, flicker, overheat, or fail. An oversized supply wastes money. The goal is to calculate total power draw and add a safety margin.
Basic Power Formula:
Total Wattage = Strip Length (meters) × Watts per Meter
Power Supply Size = Total Wattage × 1.20 (add 20% safety margin)
The 20% safety margin prevents the power supply from running at 100% capacity continuously, which generates excess heat and shortens its life. Some installers use a 25–30% margin for additional headroom.
LED Strip Types and Power Consumption:
| LED Type | Density | Watts/Meter | Watts/Foot | Lumens/Meter |
|---|---|---|---|---|
| SMD 2835 (standard) | 60 LEDs/m | 4.8 W | 1.5 W | 300–400 |
| SMD 2835 (high density) | 120 LEDs/m | 9.6 W | 2.9 W | 600–800 |
| SMD 5050 (RGB) | 60 LEDs/m | 14.4 W | 4.4 W | 700–900 |
| SMD 5050 (RGBW) | 60 LEDs/m | 18 W | 5.5 W | 800–1000 |
| SMD 5630/5730 | 60 LEDs/m | 15 W | 4.6 W | 1,200–1,500 |
| WS2812B (addressable) | 60 LEDs/m | 18 W | 5.5 W | Variable |
| COB (chip-on-board) | Continuous | 10–20 W | 3–6 W | 400–1,200 |
Voltage Options:
| Voltage | Advantages | Max Run Length |
|---|---|---|
| 12V DC | Most common, widest selection | 5 m (16 ft) per run |
| 24V DC | Longer runs, less voltage drop | 10 m (33 ft) per run |
| 48V DC | Professional installations | 20 m (66 ft) per run |
| 120V / 230V AC | Very long runs (no transformer) | 50 m (164 ft) |
Voltage Drop Problem: LED strips carry current along thin copper traces. Over long distances, resistance causes voltage to drop, making LEDs at the far end dimmer than those near the power supply. This is the main reason for maximum run length limits.
Voltage Drop Formula:
Voltage Drop = (2 × Length × Current × Resistance per meter) / 1000
To minimize voltage drop:
- Power from both ends of the strip
- Use a higher voltage (24V instead of 12V)
- Use thicker gauge wire for longer runs
- Split long runs into multiple segments with separate power injection
Wire Gauge Selection:
| Distance to Strip | Current up to 3A | Current up to 5A | Current up to 10A |
|---|---|---|---|
| Up to 5 ft (1.5 m) | 22 AWG | 20 AWG | 18 AWG |
| 5–15 ft (1.5–4.5 m) | 20 AWG | 18 AWG | 16 AWG |
| 15–30 ft (4.5–9 m) | 18 AWG | 16 AWG | 14 AWG |
| 30–50 ft (9–15 m) | 16 AWG | 14 AWG | 12 AWG |
Current Calculation:
Current (Amps) = Total Wattage / Voltage
A 5-meter strip of 5050 RGB at 14.4 W/m on 12V:
Total watts: 5 × 14.4 = 72W
Current: 72 / 12 = 6 Amps
Power supply: 72 × 1.2 = 86.4W → choose 100W supply
Power Supply Types:
- Desktop adapter (brick): Compact, plug-in, up to 120W. Best for small projects.
- Enclosed switching supply (Mean Well style): 50–600W. Metal case. Needs wiring. Best for permanent installations.
- Waterproof supply: IP67 rated. For outdoor or wet locations.
- Dimmable supply: Required if using a dimmer that modulates the DC output.
Common Mistakes: Using too small a power supply, running strips beyond maximum length without power injection, using too thin wire for long runs, and not accounting for RGBW strips drawing maximum power when set to white (all four channels on simultaneously).
Safety Note: Low-voltage LED strips (12V/24V) are safe to handle, but the power supply connects to mains voltage (120V/230V). All mains wiring must comply with local electrical codes. If you are not comfortable with mains wiring, hire a licensed electrician for the power supply installation.