This Factorio tutorial explains the design and construction of a 6 belt balancer.
Completing our planned series on Factorio belt balancers, this 6-in, 6-out belt balancer offers the highest possible throughput for train depots. Each train car can only be accessed by 6 inserters per side, so a 6-belt balanced system is ideal for clearing out all the contents as quickly as possible so your trains can move on to their next stop. This design is balanced both for input and output, so you can be sure that no matter how much goes into each belt, a balanced amount will be distributed to the outgoing belts. None of the incoming belts are neglected, either, so you won’t have individual belt backing up and causing delays in your factory.