WS2812B / NeoPixel Power Calculator
PSU size, fuse rating and an injection plan from your LED count and brightness, with the realistic-versus-worst-case choice every LED-strip thread ends up asking about. Per-LED figures: 60 mA is the WS2812B datasheet worst case (all channels full); real content averages far less.
Result
I = 300 LEDs × 20 mA = 6 A, supply = 6 A × 1.3 = 7.8 A
| Quantity | Value |
|---|---|
| Power supply | 5 V, 7.8 A (39 W) |
| Strip draw | 6 A (30 W at 5 V) |
| Strip length | 5 m at 60 LEDs per meter |
| Injection points | 3 (about every 2 m) |
| Fuse near the supply | 10 A |
The three rules of LED-strip power.
1. Never power a long strip from one end. The flex copper drops volts, and the far LEDs shift colour or flicker. Inject along the run.
2. Common ground between the supply, the strip and the microcontroller. A level shifter on the data line (3.3 to 5V) fixes most glitching.
3. Fuse the supply line near the PSU. Strips fail short, and an unfused 5V 20A supply is a fire risk.
Injection & wire guide
| Run length (5V, 60 LED/m) | Power injection | Feed wire (worst case) |
|---|---|---|
| Up to 2 m | One feed at the start is fine | 18 AWG (0.75 mm²) |
| 2–5 m | Feed both ends | 16 AWG (1.5 mm²) |
| 5–10 m | Feed every 2–3 m, and both ends | 14 AWG (2.5 mm²) bus, 18 AWG taps |
| 10 m and more | Split into segments with separate supplies, or inject every 2 m from a central bus | 12 AWG (4 mm²) bus |
Check the feed wire with the voltage drop calculator.
Worked example
5 m of 60 LED/m is 300 LEDs at 5V. Realistic animations (20 mA) draw 6 A, or 30 W. Worst-case full white (60 mA) draws 18 A, or 90 W. With 30% headroom, pick a 5V 8 A supply for animations only, or 5V 24 A if full white is ever on the menu. Inject at 0 m, 2.5 m and 5 m.
FAQ
How many amps does a 5m WS2812B strip draw?
300 LEDs draw 6 A realistic (animations) and 18 A worst case (full white) at 5V.
How often should I inject power?
Every 2–3 meters at 5V for 60 LED/m, and always at both ends. Voltage drop is the limit, not the supply.
What fuse should I use?
About 20% above the draw, within 15 cm of the PSU. 300 LEDs at full white need a 25 A fuse, or fused sub-branches.
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