How to find how many number of transactions are happening in SQL Server/SQL Server database in a day?
The Perfmon counters for Transactions/Sec and Batch Requests/Sec are cumulative counters, meaning they keep going up after the SQL Server starts up.

To get a count per day since startup, divide the counter output by the number of days that the server has been up. An easy way to do that is to check the creation date of TempDB - here's an example query, but keep in mind that rounding will be a problem if the server's been up for less than a day or two:

SELECT DATEDIFF(dd, create_date, GETDATE()) 
FROM sys.databases 
WHERE database_id = 2;


To get daily numbers going forward, consider saving the contents of that counter to a table. Then you can take a day's metric, subtract the day before, and you'll get the counter delta for that one day. (I use sp_BlitzFirst and the Power BI Dashboard for DBAs to do this with 15-minute granularity. (Disclaimer: those are open source tools that I wrote.))

Unfortunately, if you try to do daily sampling, it can be inaccurate due to:


The server restarting or clustered SQL Server service failing over
The Availability Group or database mirror transitioning roles (failing over) does not reset those counters, but you'll need to add up the transactions or batches from both replicas
If you're combining metrics from multiple replicas, keep in mind that you've also probably got monitoring software, and the monitoring software's queries are also going to be counted