The first thing to think about when you're wondering, "How do I know if we are ready to live together?" is what the level of your commitment is to each other. If one of you wants to live together to have a willing sex partner when she or he gets home from doing "her own thing" and because it saves on rent, but the other thinks it's the final step before marriage, then the answer is that no, you're not ready to live together. In fact, you may not be ready for a relationship together at all.
The next thing you must consider when you're wondering, "How do I know if we are ready to live together?" is how much you and your partner are each able and willing to compromise. The honeymoon phase of the relationship will start to fade when the toothpaste cap stays off, the toilet seat lid stays up and the wet towels are on the floor day after day. If there are some things that you've already noticed as annoying little habits, they'll annoy about ten times more when you live with them. You have to decide if that's going to be outweighed by the love and companionship you get from the relationship day in and day out.
Keep in mind too that you don't change people not often, and not much. If your idea of moving in together is changing that slob partner of yours into a neat freak, well, whoa, Nellie. You most definitely are headed down a disappointing path. If you cannot accept your partner for what and who he or she is, if you can't decide to move in together without the idea that "some things have to change then you're not ready to move in together.
Another issue that has to be resolved when you're wondering, "How do I know if we are ready to live together?" is knowing that you can come up with a good decision on where you are going to live. Will he move all his things into your home, or will you move to his? Or perhaps you'll find a brand new place together. The latter is generally the better idea, say the experts.
We can get awfully proprietary about our comfy little home. And, if we're renters we've probably chosen a home that has room for us - and only us. Overcrowding can be the kiss of death in a relationship. Finding something with the right space, that belongs equally to the two of you, may not only give you a great home that makes both of you happy but the decision-making together can help cement the relationship. It, too, can be one of the ways to determine how to tell if you are ready to move in together.