CDN Edge Distribution Calculator

Split CDN load across points of presence and check the origin request rate and egress that survives the cache hit ratio.

Inputs

Total requests per secondrps

Points of presencePoPs

Edge cache hit ratio%

Average object sizeKB

Origin capacityrps

Requests per PoP

6,250rps

Requests Reaching the Origin

20,000rps

Origin Utilisation

400.0%

Edge Egress

339.15Gbps

Origin Egress

29.49Gbps

Traffic Offloaded from the Origin

92.0%

Step by step

Values used
Total requests per second = 250,000 rps; Points of presence = 40 PoPs; Edge cache hit ratio = 92 %; Average object size = 180 KB; Origin capacity = 5,000 rps
CDN Edge Distribution
requests per PoP = total ÷ PoPs; origin requests = total × (1 − cache hit ratio); egress = request rate × object size × 8.
Requests per PoP
= 6,250 rps
Requests Reaching the Origin
= 20,000 rps
Origin Utilisation
= 400.0
Edge Egress
= 339.15 Gbps
Origin Egress
= 29.49 Gbps
Traffic Offloaded from the Origin
= 92.0

How it works

Anycast routing spreads requests roughly evenly across points of presence, and everything the edge can answer never reaches the origin. The miss fraction is what determines origin sizing, and because it multiplies the full object size it dominates origin egress cost. Cache hit ratio has brutal leverage on origin load: dropping from 95% to 90% doubles the requests hitting your origin, which is why cache-key and TTL design is a capacity decision, not a tuning detail.

Formula

CDN Edge Distribution

requests per PoP = total ÷ PoPs; origin requests = total × (1 − cache hit ratio); egress = request rate × object size × 8.

hit: Fraction of requests answered from the edge cache
originEgress: Bandwidth the origin must still serve for cache misses and revalidation

Frequently Asked Questions

How is CDN Edge Distribution calculated?

requests per PoP = total ÷ PoPs; origin requests = total × (1 − cache hit ratio); egress = request rate × object size × 8. Anycast routing spreads requests roughly evenly across points of presence, and everything the edge can answer never reaches the origin. The miss fraction is what determines origin sizing, and because it multiplies the full object size it dominates origin egress cost.

Why does CDN Edge Distribution matter?

Cache hit ratio has brutal leverage on origin load: dropping from 95% to 90% doubles the requests hitting your origin, which is why cache-key and TTL design is a capacity decision, not a tuning detail.

What values do I need to enter?

This calculator takes 5 inputs: Total requests per second, Points of presence, Edge cache hit ratio, Average object size, Origin capacity. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.

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