Size CDN and origin bandwidth from visitors, page weight and a peak-to-average ratio instead of a monthly average.
A monthly average hides the busy hour, so the average bit rate is multiplied by a peak-to-average ratio to get the figure your links and origin must actually survive. Only the miss fraction reaches the origin, which is why a high cache hit ratio shrinks origin bandwidth far faster than it shrinks CDN volume. CDN contracts and origin egress are sold on peak Mbps or committed volume, and origin capacity has to be built for the peak miss rate — sizing on the average is how a launch saturates the origin uplink while the CDN reports plenty of headroom.
CDN Bandwidth
average Mbps = total bytes × 8 ÷ seconds in the month; peak Gbps = average × peak-to-average ratio ÷ 1,000; origin peak = peak × (1 − cache hit ratio).
average Mbps = total bytes × 8 ÷ seconds in the month; peak Gbps = average × peak-to-average ratio ÷ 1,000; origin peak = peak × (1 − cache hit ratio). A monthly average hides the busy hour, so the average bit rate is multiplied by a peak-to-average ratio to get the figure your links and origin must actually survive. Only the miss fraction reaches the origin, which is why a high cache hit ratio shrinks origin bandwidth far faster than it shrinks CDN volume.
CDN contracts and origin egress are sold on peak Mbps or committed volume, and origin capacity has to be built for the peak miss rate — sizing on the average is how a launch saturates the origin uplink while the CDN reports plenty of headroom.
This calculator takes 6 inputs: Monthly visitors, Page views per visit, Average page weight, HTTP requests per page view, Edge cache hit ratio, Peak-to-average ratio. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.