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I was making a coal liquefaction build using manual math for exact numbers when I noticed that the heavy oil/s in the Recipe crafting throughput tooltip (RCTT) was incorrect.
After toying around for a bit I realized that this only happens when the refinery has productivity.
Every other number in the RCTT is correct.
The error gets worse with higher speed and/or higher productivity.

A few examples:

A refinery with three Prod2 mods in it. The heavy oil/s shows 14.2/s, but lets calculate it manually.
[Heavy Oil per Craft] / [Time per Craft] * {Machine Speed] * {Productivity]
90 / 5 * 0.7 * 1.18 = 14.868/s
An error of ~0.7/s

A maxed vanilla refinery shows 143/s.
90 / 5 * 6.55 * 1.3 = 153.27/s
An error of ~10/s

And finally, a maxed legendary everything refinery shows 1.7k heavy oil/s.
90 / 5 * 63.875 * 1.75 = 2012.0625
An error upwards of 300/s, which is about 15%.

I also looked through the other refinery recipes and found no other errors, but I have no way of knowing if this is the only instance of this.

Small test world I made:

Thelaststandn wrote: Thu Apr 17, 2025 6:57 am [Heavy Oil per Craft] / [Time per Craft] * {Machine Speed] * {Productivity]
90 / 5 * 0.7 * 1.18 = 14.868/s

This seem incorrect calculation to me, in that i think there is an additionnal thing to consider , productivity doesn't apply to all the heavy oil per craft, some of it being used as input for the receipe, this amount need be subtracted to the 90 as it would be considered "cayalyst"

mmmPI wrote: Thu Apr 17, 2025 7:19 am

Thelaststandn wrote: Thu Apr 17, 2025 6:57 am [Heavy Oil per Craft] / [Time per Craft] * {Machine Speed] * {Productivity]
90 / 5 * 0.7 * 1.18 = 14.868/s

This seem incorrect calculation to me, in that i think there is an additionnal thing to consider , productivity doesn't apply to all the heavy oil per craft, some of it being used as input for the receipe, this amount need be subtracted to the 90 as it would be considered "cayalyst"

The game doesn't do that. The input and output are handled separately.
Here's a refinery with no productivity.
90 / 5 * 1 * 1 = 18/s
Which matches the number in the screenshot.

Thelaststandn wrote: Thu Apr 17, 2025 7:45 am The game doesn't do that. The input and output are handled separately.

Here is the wiki part where it's explained :

Some recipes consume some of the same items or fluids as they generate. These items are "catalysts" in that recipe. In those cases, productivity bonuses usually do not apply to the catalytic portion of the output, only to any net-gains of material.

https://wiki.factorio.com/Productivity#Catalysts

mmmPI wrote: Thu Apr 17, 2025 7:57 am

Thelaststandn wrote: Thu Apr 17, 2025 7:45 am The game doesn't do that. The input and output are handled separately.

Here is the wiki part where it's explained :

Some recipes consume some of the same items or fluids as they generate. These items are "catalysts" in that recipe. In those cases, productivity bonuses usually do not apply to the catalytic portion of the output, only to any net-gains of material.

https://wiki.factorio.com/Productivity#Catalysts

Huh wow, my bad. That is certainly one of the mechanics of all time.
Guess I need to re-do my math again, yay
I do feel dumb, but I wish the game had a better way of communicating the no-productivity-on-catalyst to the player.
What do I do with this post now? Just wait for a mod to nuke it or what

Thelaststandn wrote: Thu Apr 17, 2025 6:57 am And finally, a maxed legendary everything refinery shows 1.7k heavy oil/s.
90 / 5 * 63.875 * 1.75 = 2012.0625
An error upwards of 300/s, which is about 15%.
Bug3.PNG

Quick check assuming left side is correct:
319÷25 = 12.76 crafts per second
12.76*(90 + 65*0.75) = 1770.45.
65 is amount of heavy oil given by bonus cycles as they do not give catalyst.

Your math is wrong. Not a bug.

Quick check assuming left side is correct:
319÷25 = 12.76 crafts per second
12.76*(90 + 65*0.75) = 1770.45.
65 is amount of heavy oil given by bonus cycles as they do not give catalyst.

Yea I didn't know about catalyst restrictions.
But Would you mind explaining the math you're doing here? I want to understand it but I don't know where your getting some of those numbers from.

Thelaststandn wrote: Thu Apr 17, 2025 8:37 am Yea I didn't know about catalyst restrictions.
But Would you mind explaining the math you're doing here? I want to understand it but I don't know where your getting some of those numbers from.

As far as i can tell this is correct :

mmmPI wrote: Thu Apr 17, 2025 7:19 am productivity doesn't apply to all the heavy oil per craft, some of it being used as input for the receipe, this amount need be subtracted to the 90 as it would be considered "cayalyst"

the receipe output 90 heavy oil, but require 25 as input, the productivity only applies to 90-25 = 65 heavy oil

The rest of your math seem correct like the crafting speed and time of the receipe relation, you just need to subtract the amount of product in the outpout that is also in the input before you try to apply productivity.

Thelaststandn wrote: Thu Apr 17, 2025 8:37 am But Would you mind explaining the math you're doing here? I want to understand it but I don't know where your getting some of those numbers from.

12.76 is crafting speed
90 is product given by normal crafts (it consists of 25 catalyst that is given back and 65 new product)
65 is product given by bonus crafts (it only consists of 65 new product)
0.75 is productivity bonus

Still not 100% sure how it works, but I should at leat have the tools to figure it out when I'm less sleep deprived.
Thank you both for the help.