DMX Universe Calculator

512 channels, 170 pixels

A DMX universe has 512 channels. An RGB pixel uses three of them, one each for red, green and blue. 512 divided by 3 gives 170 whole pixels per universe with two channels left over. RGBW pixels fit 128 per universe, 16-bit RGB pixels 85.

The calculator only puts whole pixels into a universe: pixel 171 starts at channel 1 of the next universe. Every output also starts its own universe, the way most pixel controllers patch.

Universes in Art-Net and sACN

Art-Net counts from universe 0 and addresses via Net (0–127), Sub-Net (0–15) and Universe (0–15), which together form a 15-bit address up to 32,767. sACN (E1.31) starts at universe 1 and goes up to 63,999; every universe has its own multicast address in the 239.255.x.y range.

Make sure software and controller count the same way. An off-by-one universe is the most common patching mistake. More in the article Art-Net vs. sACN.

Network load and frame rate

Every universe goes out as its own packet per frame, so at 40 fps that is 40 packets per second per universe. A full Art-Net packet is 530 bytes, an sACN packet 638 bytes. A 100 Mbit network carries a few hundred universes; beyond that, gigabit is worth it.

Independent of the network, the pixel chain itself limits the frame rate. 800 kHz pixels such as the WS2812B need 30 µs per RGB pixel. With 1,000 pixels on one port you get about 33 fps at most.