CDN Cache Hit Ratio Calculator

Turn edge hits and misses into a cache hit ratio, origin offload and the origin egress the cache actually avoids.

About CDN Cache Hit Ratio Calculator

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.

Formula

CDN Cache Hit Ratio

hit ratio = hits ÷ (hits + misses); origin offload = hit ratio × delivered traffic; origin traffic = (1 − hit ratio) × delivered traffic.

hit ratio: Share of requests answered from an edge cache
origin offload: Traffic the edge served so the origin never saw it
origin egress avoided: Offloaded traffic priced at your origin egress rate

Worked example

With the default values below, CDN Cache Hit Ratio Calculator returns Cache Hit Ratio of 92.00%. Change any input above and every figure here is recalculated in your browser.

Inputs used

Edge cache hitsaccepts 0–1,000,000 million requests: 920 million requests
Edge cache missesaccepts 0–1,000,000 million requests: 80 million requests
Traffic delivered to usersaccepts 0–1,000,000 TB/month: 500 TB/month
CDN delivery priceaccepts 0–10 USD/GB: 0.085 USD/GB
Origin egress priceaccepts 0–10 USD/GB: 0.09 USD/GB

Results

Cache Hit Ratio: 92.00%
Cache Miss Ratio: 8.00%
Traffic Served Without Touching Origin: 460.00 TB
Traffic Pulled From Origin: 40.00 TB
CDN Delivery Charge: $43,520.00
Origin Egress Charge: $3,686.40
Origin Egress Avoided by Caching: $42,393.60
Total Delivery Cost: $47,206.40

Step by step

1Values used
2CDN Cache Hit Ratio
3Cache Hit Ratio= 92.00
4Cache Miss Ratio= 8.00
5Traffic Served Without Touching Origin= 460.00 TB
6Traffic Pulled From Origin= 40.00 TB
7CDN Delivery Charge= 43,520.00
8Origin Egress Charge= 3,686.40

Assumptions and limits

The result is derived only from the 5 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax or compounding frequency into account.
Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

How is CDN Cache Hit Ratio calculated?

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.

Why does CDN Cache Hit Ratio matter?

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.

What values do I need to enter?

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.

Should I measure hit ratio by requests or by bytes?

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.