Support for concurrent thread is basically depends on many factors like OS, free RAM and connections.
This is based on my experience If we follow the best practices as follow then we can achieve 350 ~ 500 concurrent users (web based application) and 900~1100 concurrent users (backend API) provided 8 GB RAM with 64-bit OS.
- Use latest version of JMeter
- Use correct number of Threads
- Use script parameterization & correlations
- Use CLI mode, disable/remove listeners, CSV out over XML, less assertions
- Use variable sharing between threads & thread groups
- Placement of Cookies, Authorization Manager
- Don’t use functional mode
- Don't modify jmeter.properties instead modify user.properties file
- Don’t use Deprecated elements
Note: If you observe CPU is crossing 80% then that’s not a good indication. You should minimize the concurrent users count and rerun the script.