We have roughly 6,000 flat sorting machines. They operate about 17 hours per day. They handle 35,000 pieces of flat mail per hour.

But let's be conservative and assume it's:
5,000 machines
30,000 pieces per hour
8 hours a day.

To save you the math, that's 1.2 Billion pieces a day, running at less than half of average.

The Postal Service processes and delivers 472.1 million mail pieces each day. We have a lot of excess capacity.


Unfortunately, there is no one article that provides all of that. Here are a few that provide the stats above, and I have verified it with other articles over the months:

https://facts.usps.com/one-day/

https://www.uspsoig.gov/blog/fss-comes-short

https://www.npr.org/2020/08/19/903982558/dismantling-mail-sorting-machines-could-leave-a-lasting-mark-on-the-postal-servi

Or you can simplify a bit of the math from this statement by the American Postal Workers Union (which should know):

"According to a grievance filed by the American Postal Workers Union and obtained by The Washington Post, the USPS was poised to decommission 671 of the massive machines, roughly 10% of its inventory, and capable of sorting 21.4 million pieces of paper mail per hour. The Postal Service, by comparison, processes as much as 500 million items each day.

https://www.adn.com/nation-world/2020/08/20/heres-why-the-postal-service-wanted-to-remove-hundreds-of-mail-sorting-machines/


I'd suggest questioning a lot of stuff you read on the internet.