Topic
If the Enterprise Edition of Nintex Workflow is installed a total of the in progress workflows can be viewed in Central Administration > Nintex Workflow Management (Nintex Administration for 2016 - ) > Administration Reports by selecting the "Workflows By Site" report.
If the Enterprise Edition of Nintex Workflow is not installed or you would like more details such as the total of a particular workflow an SQL query can be performed.
Instructions
Run the following SQL query on the Nintex Workflow content DB relevant to the site collection that the site exists in.
SELECT * from workflowinstance
where SiteID = 'YouSiteIDGUIDHere'
and State = '2'
SELECT * from workflowinstance
where SiteID = 'YouSiteIDGUIDHere'
and State = '2'