CDN Cache Hit Ratio Calculator

hit ratio = hits ÷ (hits + misses); origin offload = hit ratio × delivered traffic; origin traffic = (1 − hit ratio) × delivered traffic. The ratio is counted in requests, but the money is in bytes: every miss forces a fetch that you pay for twice, once as origin egress and again as CDN delivery. Multiplying the miss ratio by delivered traffic gives the origin pull, and the remainder is the offload that only costs the CDN rate.

Cache hit ratio is the single lever that decides how much origin capacity and egress you buy — lifting 88% to 95% removes more than half the origin traffic. Confirm both the CDN and origin egress rates with your providers, because volume commitments move them a long way from list price.

This calculator takes 5 inputs: Edge cache hits, Edge cache misses, Traffic delivered to users, CDN delivery price, Origin egress price. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.

Track both. Request hit ratio tells you how well the cache key and TTLs are working; byte hit ratio tells you what you are paying, and it is usually lower because large objects are the ones most often missed or range-requested.