I have ordered shoes but am not sure the size is correct

You should have half to a full thumbnails width between the end of the shoe and your longest toe while standing and fully weight bearing. The reason for this is that your feet will swell throughout the day and it's important to have enough space to accommodate for any swelling. If you have less than half a thumbnails width, you may want to exchange for a larger size.

If you have more than an a full thumbnails width, you may want to exchange for a smaller size. However, it is important to note that it's always better to have a little more space than too little when it comes to your shoes.