Knowing the ratio of factorio is an important thing to build a perfect factory. So, with that being said let’s see how the ratios work.
How to calculate
In order to calculate the ratio on factorio, you have to hover your mouse to the desired item. Now you should see the item info. If you look in the bottom part you’ll be able to see the crafting time. Here you need to go for each item required to see how much time it takes to be crafted. Repeat this process over and over until you are on the last item. 
Here is a picture of how the process should be. Suppose you want to have a throughput of 30gears/sec. You will need 30 assemblers level 1, 192 furnaces and 120 drills on iron, and lastly 9 drills on coal.
Factorio calculator
Some fans of Factorio created a website which can be reached here, to calculate every ratio to have a specific factory. Using this calculator is pretty easy. In order to change the item click on the red circuit, and a menu with all the items on factorio will appear. Search by text or scroll the desired item. Once you’ve selected the right item make sure to go on the settings tab and select all the right options, which can be the level of the assemblers, furnaces, belts, and so on. Now go back to the Factory tab and if selected everything correctly you should be able to see what you need. The last thing you need to do is change the total factories or items/min. Changing those values will automatically update the whole calculator.
And that’s all. Ratios are pretty simple to handle but a bit nasty while learning them the first time. Make sure you join our discord server here to find more people interested in this game. If you want to know more about factorio check this guide out.
