On Windows, go to Settings > System > Display > Advanced display
Check the Refresh rate field
On macOS, go to System Settings > Displays
Check the Refresh Rate option
On Linux, open Display Settings
Check the refresh rate listed for the monitor
On the monitor itself, open the on-screen display menu
Look for refresh rate or signal information
In your graphics card control panel, check display properties
In games or apps, open video or display settings
Use a refresh rate test website in a browser
Use a monitor information tool or system diagnostics app