If you didn't take an OG then it's all guess work. Using your gages takes all the guess work out of your process.
Using the airlock as a gage as to whether or not the brew's done fermenting is NOT recommended.
Was it a kit? The recipe should give you an indicator of the OG/FG. If you used the right amount of water you should be close.
You need to post your recipe so the numbers can be placed into a database to get an answer. I don't have one, but someone will probably check in who does.