On your iPhone, go to Settings > General > iPhone Storage to learn how much storage you’re using, how you’re using it, and how much you have left. On other smartphones, go to Settings > Device > Storage.
If you’re nearing your limit with a lot of apps, music, or photos, it’s a good idea to consider a larger capacity.
If you’re not using a lot of storage and rarely download apps or don’t take many photos, an iPhone with a smaller capacity may be better for you.