Network bandwidth calculators: What will be my WAN's link speed?
Use this recommended bandwidth calculator to calculate network latency and your WAN's link speed. Our network administration expert says this tool can simulate 1,000 users in your environment.
To simulate 1,000 users, I would recommend changing the Request Size to something greater than 10,000. Then select the various link speeds to review the overall latency provided by the users. With the information provided, it is hard to actually provide an accurate heuristic/formula for helping you. But this should provide you the basics of what you need. It's by far my favorite latency calculator. You'll also notice at the top of the window, several other resources and utilities that will help you with approximating link speed.