My organization was promised the ability to use two number widgets in the dashboard and make simple calculations such as calculating conversion rates. Unfortunately, we are still not able to do this.
While we wait monday to implement that feature, I just wanted to let you know that you can do that with our Screenful Reports add-on. Our new Table chart allows doing calculations across different monday boards. You can also do calculations between sums of columns, not just individual rows. The resulting chart can be placed on a monday dashboard.
Our organisation are also waiting on this feature… hope an admin can provide an update on this. I see many other similar threads for this dating back to 2019.