library documentation

Each individual NeoPixel draws up to 60 milliamps at maximum brightness white (red + green + blue). In actual use though, it’s rare for all pixels to be turned on that way. When mixing colors and displaying animations, the current draw will be much less. It’s impossible to estimate a single number for all circumstances, but we’ve been using 1/3 this (20 mA per pixel) as a gross rule of thumb with no ill effects. But if you know for a fact that you need every pixel on at maximum brightness, use the full 60 mA figure.