It's html and css, so you will have to play increasing the widht and reducing font size. You can also play with the overflow css keyword, as the default is "hidden" (anything that does not fit, hide it). There is no exact anything, you will have to play with the files to fit your needs. It depends also on the browser , operating system, etc.

If you have a name like "Roberts Conference Room" then you will need extra wide buttons.

Best regards,