Is there a header sizes reference somewhere?

Hello,

In almost every website I build, I want to change from the default font size of at least 1, usually a few, of the headers. Is there a way I can find out what the default sizes are. Every time I have to just guess and pick a number and then go back and forth and see if it is different, etc. If I just knew that H1 was 22px, for example, I wouldn’t have to use trial and error to set a new size. I’d pick a new pixel size empowered with that knowledge!