Units & conversions
Most bad cost estimates start as unit mistakes. Convert explicitly before you model pricing tiers.
Quick conversions
- Mbps �?MB/s: divide by 8 (megabits to megabytes).
- GB �?GiB: GB is decimal (10^9 bytes). GiB is binary (2^30 bytes). 1 GiB �?1.074 GB.
- Per 10k vs per 1M: normalize pricing units first (a 100× error is common).
- Hours/month: for estimates, 730 is a typical month; adjust for schedules.
Throughput �?monthly GB
A safe workflow for transfer estimates:
- Convert Mbps to MB/s (divide by 8).
- Multiply by a utilization factor (average / peak).
- Multiply by seconds/day and hours/day (or 730h/month for always-on).
- Convert MB to GB (divide by 1000 if your pricing is per GB).
Example: 50 Mbps average, 12 hours/day �?(50/8) MB/s × 12 × 3600 × 30 / 1000 �?810 GB/month.
How to get your inputs
- Requests: load balancer metrics, API gateway metrics, or application dashboards (RPS).
- Transfer: CDN origin egress, load balancer processed bytes, or VPC flow logs summaries.
- Storage: allocated vs used (billing often charges allocated, monitoring often shows used).
- Time: scheduled uptime (work hours) vs always-on (730h/month).
Common mistakes (and how to avoid them)
- Mixing bits and bytes: “Mb�?is bits; “MB�?is bytes. Double-check the capital B.
- Using GiB numbers with GB pricing: convert before multiplying by $/GB.
- Assuming 100% utilization: average throughput is often far lower than peak.
- Forgetting per-request unit size: “per 10k�?vs “per 1M�?changes everything.
- Using the wrong month length: scheduled workloads rarely run 730 hours.
Validate after you deploy
- Compare estimated monthly GB to actual “bytes transferred�?in your provider metrics.
- In billing/Cost Explorer, group by usage type and confirm the unit (GB, requests, hours).
- Re-check after traffic changes: launches, batch jobs, and incident retries can shift averages fast.
Apply conversions to cost drivers
- Convert throughput to monthly GB before using transfer or CDN calculators.
- Normalize request units (per 1k, per 10k, per 1M) before multiplying by volume.
- Convert GiB to GB if pricing is decimal, then use the storage calculators.
- Use a consistent hours/month assumption across all compute estimates.
Scenario planning
- Baseline: average throughput and request rates with normal utilization.
- Peak: higher throughput and request volume during launch or incident weeks.
- Scheduled workloads: compare 730 hours vs your real schedule.
- Unit drift: keep a checklist for GB vs GiB and per-1k vs per-1M.
Validate after changes
- Confirm units in billing exports match your calculator inputs.
- Re-check conversions after switching providers or regions.
- Validate monthly totals against a real week of metrics.
1 unit tools
Sources
- AWS data transfer pricing (GB units vary by service): AWS EC2 On-Demand pricing
- Example of AWS documentation using decimal GB units in storage contexts: Amazon S3 User Guide
Assumptions: pricing pages use the provider’s billing units (often decimal GB). Convert your monitoring numbers to the same unit before multiplying by rates.
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