Calculator Inputs
Example Data Table
Illustrative scenarios for benchmarking. Values are sample planning references.
| Scenario | Traffic (TB) | Requests (M) | Byte Hit Ratio | Before Cost | After Cost | Net Savings |
|---|---|---|---|---|---|---|
| Media Site | 25 | 100 | 60% | $2,942.00 | $2,560.96 | $381.04 |
| SaaS Platform | 60 | 260 | 75% | $6,273.60 | $4,695.74 | $1,577.86 |
| Large Content Network | 120 | 520 | 82% | $11,792.80 | $7,837.96 | $3,954.84 |
Formula Used
1) Total monthly traffic in GB
Total Traffic GB = Monthly Traffic TB × 1024
2) Cacheable traffic in GB
Cacheable GB = Total Traffic GB × Cacheable Traffic Share
3) Traffic offloaded from origin
Offloaded GB = Cacheable GB × Byte Hit Ratio
4) Origin traffic after CDN
Origin After GB = Total Traffic GB − Offloaded GB
5) Offloaded requests
Offloaded Requests = Total Requests × Cacheable Request Share × Request Hit Ratio
6) Cost before CDN
Before Total = Origin Egress Cost + Origin Request Cost + Origin Infrastructure Before
7) Cost after CDN
After Total = Origin Egress After + Origin Request After + CDN Delivery Cost + CDN Request Cost + Origin Infrastructure After + CDN Fixed Fee
8) Net savings
Net Savings = Before Total − After Total
9) Annual savings
Annual Savings = Net Savings × 12
10) Payback period
Payback Months = Setup Cost ÷ Net Savings, when savings are positive
How to Use This Calculator
- Enter your total monthly outbound traffic in terabytes.
- Enter estimated monthly user requests in millions.
- Set the share of traffic and requests that can be cached.
- Enter byte hit ratio and request hit ratio assumptions.
- Add current origin egress and origin request handling costs.
- Enter CDN delivery, CDN request, and fixed monthly fees.
- Add origin infrastructure costs before and after CDN rollout.
- Include one-time setup cost to estimate payback months.
- Click Calculate Savings to show results above the form.
- Use the CSV and PDF buttons to export the calculated summary.
Frequently Asked Questions
1. What does CDN offload mean?
CDN offload is the portion of traffic or requests served from edge cache instead of the origin. Higher offload usually reduces origin bandwidth, request load, and infrastructure pressure.
2. Why use both byte hit ratio and request hit ratio?
Byte hit ratio measures cached traffic volume. Request hit ratio measures cached request count. Large files can skew traffic savings even when request savings look moderate.
3. Can CDN savings ever be negative?
Yes. If CDN pricing, low cacheability, or weak hit ratios outweigh origin savings, the model can show a monthly loss instead of savings.
4. What is a good byte hit ratio?
It depends on content type. Static assets often achieve much higher values than personalized or short-lived content. The best ratio is the one that produces measurable net value.
5. Should all traffic be counted as cacheable?
No. APIs, personalized pages, authenticated sessions, and dynamic responses often reduce cacheability. Enter realistic shares to avoid overstating savings.
6. Does this include latency or conversion benefits?
No. This model focuses on infrastructure and delivery economics. Better latency may create extra business value, but that benefit is outside these core cost equations.
7. What does break-even byte hit ratio show?
It estimates the byte hit ratio needed for the monthly CDN model to stop losing money, while keeping other entered assumptions unchanged.
8. When should I update the inputs?
Update inputs whenever pricing changes, traffic grows, cache rules improve, or application behavior shifts. Rechecking quarterly usually keeps planning assumptions more accurate.