CDN cost per GB: how to estimate bandwidth pricing

The fastest way to estimate CDN bandwidth spend is a clean $/GB model, but you must normalize region mix and tiered pricing first. Use this guide to avoid under-estimating.

Step 1: Get monthly GB delivered

• Use CDN analytics if available.
• If you only have throughput, convert Mbps to GB/month before pricing.
• Model baseline and peak months separately.

Step 2: Apply region mix

• Split traffic by pricing regions (North America, Europe, APAC, etc.).
• Apply the correct $/GB per region and sum the totals.
• If you only have a blended rate, validate it against a real bill.

Step 3: Account for tiered pricing

• Some providers lower $/GB after specific volume tiers.
• Either compute each tier explicitly or use a blended rate for your expected volume.
• Do not use the lowest tier price for the entire month.

Step 4: Check free allowances and discounts

• Subtract free bandwidth before applying $/GB rates.
• Apply committed-use or enterprise discounts if you have them.

Effective $/GB formula (fast sanity check)

• Effective $/GB = total bandwidth charges / total GB delivered.
• Use this to back-calc a blended rate from a real bill, then reuse it for planning.

Example calculation

If you delivered 8,000 GB with $420 of bandwidth charges, your effective rate is $420 / 8,000 = $0.0525 per GB. Use that blended rate for the next month unless your region mix or tier changes.

Validate with a peak scenario

• Peak months often shift region mix and cache hit rate.
• Use a higher GB/month and re-run the tiered pricing math.
• Compare effective $/GB for baseline vs peak so you do not under-budget.

Cache behavior still matters

• Edge GB is billed regardless of hit rate, but cache misses can add origin egress costs.
• If your hit rate drops during deploys or incidents, your total spend can rise even with similar edge GB.

Region mix example

If 60% of your traffic is in North America at $0.05/GB and 40% is in APAC at $0.09/GB, your blended rate is (0.6 x 0.05) + (0.4 x 0.09) = $0.066/GB. That blended rate is what you should use for quick planning.

Validation checklist

• Compare your blended rate to the last invoice to confirm it is realistic.
• Check for traffic shifts to higher priced regions.
• Recalculate after major content changes (video, downloads, or large payloads).

Units and rounding pitfalls

• Some providers bill in decimal GB, others in GiB; confirm before comparing.
• Billing dashboards may round at the line item level, which shifts the blended rate.
• Always compare on the same unit basis when benchmarking.

When $/GB is not enough

• High request volume: request fees can exceed bandwidth spend.
• Low cache hit rate: origin egress can add a second bill.
• Security add-ons: WAF and bot mitigation are request-driven.

What this does not include

• Request fees: often billed per 10k or per 1M requests.
• Origin egress: cache fill billed by your origin provider.
• Log or analytics add-ons: some providers bill these separately.

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