If I have an octocore CPU but I have written an application

If I have an octo-core CPU but I have written an application as single-threaded rather than multi-threaded, what is the maximum percentage of the CPU the application will use?

If the application is single threaded it will run on 1 core out 8 cores, unless there are multiple instances of application running.

Hence maximum CPU utilization would be 1/8 = 12.5%