Here is a graph of one of the interfaces on my router , this interface has 10 miners using it .
notice these values are the throughput not the bandwidth, now bandwidth is actually the maximum throughput that you can have, where throughout is the real-time packet/data rate , which means your bandwidth needs to be more than whatever the throughput shows here or else you will have a lot of troubles, latency and many other factors affect all these statistics, but to be on the safe side i would allocate at least 5kbps for each miner.