There are a few things to consider when trying to get accurate font sizes in Excel. First, the default font size in Excel is 11pt. This can be changed by going to File > Options > Advanced, and then scrolling down to the Display section. Here, you can change the default font size to another pt value. However, keep in mind that changing the default font size will change it for all new workbooks that are created.
Another thing to consider is that different fonts have different default sizes. For example, Arial has a default font size of 10pt, while Times New Roman has a default font size of 12pt. So, if you're using a different font than the default Excel font, you'll need to adjust your pt values accordingly.
Finally, it's important to note that Excel doesn't use traditional "font sizes". Rather, it uses what's called "point size", which is a measure of the height of the character from the top of the ascender to the bottom of the descender. So, when you're trying to get accurate font sizes in Excel, you'll need to convert from traditional font sizes to point sizes.
Here's a quick rundown of how to do that:
Keep these conversion rates in mind when setting your font sizes in Excel, and you should be able to get pretty accurate results.