Factorio Forums

How does the speed value for transport belts relate to throughput?

the wiki page
https://wiki.factorio.com/Belt_transpor ... Throughput

has the following throughput values and says the formula is speed * density = throughput
yellow: 13.333
red: 26.666
blue: 40

in the game files the belts have speed values of
yellow: 0.03125
red: 0.0625
blue: 0.09375

If we solve for density using the speed and throughput, the density comes out to ~426.66667

So a creating a belt with a throughput of 20 items per second would be 20/426.6667 = 0.04698?

My question is does this density number represent? Is this tile size / item size? Can this be changed or modded? Would the 426.66667 number be a safe bet for calculating belt throughput on the fly?

in the game files the belts have speed values of
yellow: 0.03125
red: 0.0625
blue: 0.09375

This is in tiles/tick units. 1 second = 60 ticks. The game internally represents time values in number of ticks, so the game files often use this as well.

So the actual speed in tiles/second:
yellow: 1.875
red: 3.75
blue: 5.625

Solving for density:
13.333 / 1.875 = 7.111

But that's including both lanes, single lane would be:
7.111 / 2 = 3.555

Which is exactly:
32 / 9 = 3.555

Because a belt lane internally has 32 spaces and each item takes 9 spaces.

Belt speeds expressed in terms of spaces/tick actually are:
yellow: 1 space/tick
red: 2 spaces/tick
blue: 3 spaces/tick

Belt speeds can be modded, number of spaces per belt tile and sizes of items cannot.

Thanks Yoyobuae, great breakdown! figured it was something simple.