Turn user population into average and peak DNS query rates and the number of resolvers required.
Average rate comes straight from population and per-user query volume; the peak factor accounts for login storms and morning ramp-up. Only the cache-miss fraction reaches upstream, and resolver count is sized on peak with one spare unit. DNS is on the critical path for every session, so it must be sized for the peak second rather than the daily average — a resolver that saturates during a login storm looks to users like a total outage.
DNS Query Rate
average qps = users × queries per hour ÷ 3600; peak qps = average × peak factor.
Load reaching authoritative servers
upstream qps = peak qps × (1 − cache hit ratio)
average qps = users × queries per hour ÷ 3600; peak qps = average × peak factor. Average rate comes straight from population and per-user query volume; the peak factor accounts for login storms and morning ramp-up. Only the cache-miss fraction reaches upstream, and resolver count is sized on peak with one spare unit.
DNS is on the critical path for every session, so it must be sized for the peak second rather than the daily average — a resolver that saturates during a login storm looks to users like a total outage.
This calculator takes 5 inputs: Users or devices, Queries per user per hour, Peak-to-average factor, Resolver cache hit ratio, Capacity per resolver. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.