I doubt if any one knows the answer. However, if we're talking about the big ones... say 30 feet or higher, there could be up to a hundred or more. These include the Great Pyramid complex and other huge Pyramids in Egypt; those in the USA, Iraq, Mexico, South America, China, New Zealand, and a variety of those located in the Sudan, along with under-sea structures featured over the years in the Pyramid Guide newsletter. Many grown-over pyramids known to exist, are yet to be unearthed in Mexico, Central and South America. Perhaps several hundred pyramids as monuments of lesser height could be added the world over. Although an exciting and worthwhile endeavor, I stopped counting these twenty years ago, as a plethora of new reports were continually turning up in the mail.