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plugins/azure-cloud-development/skills/azure-pricing/references/COST-ESTIMATOR.md

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+# Cost Estimator Reference
+
+Formulas and patterns for converting Azure unit prices into monthly and annual cost estimates.
+
+## Standard Time-Based Calculations
+
+### Hours per Month
+
+Azure uses **730 hours/month** as the standard billing period (365 days × 24 hours / 12 months).
+
+```
+Monthly Cost = Unit Price per Hour × 730
+Annual Cost  = Monthly Cost × 12
+```
+
+### Common Multipliers
+
+| Period | Hours | Calculation |
+|--------|-------|-------------|
+| 1 Hour | 1 | Unit price |
+| 1 Day | 24 | Unit price × 24 |
+| 1 Week | 168 | Unit price × 168 |
+| 1 Month | 730 | Unit price × 730 |
+| 1 Year | 8,760 | Unit price × 8,760 |
+
+## Service-Specific Formulas
+
+### Virtual Machines (Compute)
+
+```
+Monthly Cost = hourly price × 730
+```
+
+For VMs that run only business hours (8h/day, 22 days/month):
+```
+Monthly Cost = hourly price × 176
+```
+
+### Azure Functions
+
+```
+Execution Cost = price per execution × number of executions
+Compute Cost   = price per GB-s × (memory in GB × execution time in seconds × number of executions)
+Total Monthly  = Execution Cost + Compute Cost
+```
+
+Free grant: 1M executions and 400,000 GB-s per month.
+
+### Azure Blob Storage
+
+```
+Storage Cost   = price per GB × storage in GB
+Transaction Cost = price per 10,000 ops × (operations / 10,000)
+Egress Cost    = price per GB × egress in GB
+Total Monthly  = Storage Cost + Transaction Cost + Egress Cost
+```
+
+### Azure Cosmos DB
+
+#### Provisioned Throughput
+```
+Monthly Cost = (RU/s / 100) × price per 100 RU/s × 730
+```
+
+#### Serverless
+```
+Monthly Cost = (total RUs consumed / 1,000,000) × price per 1M RUs
+```
+
+### Azure SQL Database
+
+#### DTU Model
+```
+Monthly Cost = price per DTU × DTUs × 730
+```
+
+#### vCore Model
+```
+Monthly Cost = vCore price × vCores × 730  +  storage price per GB × storage GB
+```
+
+### Azure Kubernetes Service (AKS)
+
+```
+Monthly Cost = node VM price × 730 × number of nodes
+```
+
+Control plane is free for standard tier.
+
+### Azure App Service
+
+```
+Monthly Cost = plan price × 730 (for hourly-priced plans)
+```
+
+Or flat monthly price for fixed-tier plans.
+
+### Azure OpenAI
+
+```
+Monthly Cost = (input tokens / 1000) × input price per 1K tokens
+             + (output tokens / 1000) × output price per 1K tokens
+```
+
+## Reservation vs. Pay-As-You-Go Comparison
+
+When presenting pricing options, always show the comparison:
+
+```
+| Pricing Model | Monthly Cost | Annual Cost | Savings vs. PAYG |
+|---------------|-------------|-------------|------------------|
+| Pay-As-You-Go | $X | $Y | — |
+| 1-Year Reserved | $A | $B | Z% |
+| 3-Year Reserved | $C | $D | W% |
+| Savings Plan (1yr) | $E | $F | V% |
+| Savings Plan (3yr) | $G | $H | U% |
+| Spot (if available) | $I | N/A | T% |
+```
+
+Savings percentage formula:
+```
+Savings % = ((PAYG Price - Reserved Price) / PAYG Price) × 100
+```
+
+## Cost Summary Table Template
+
+Always present results in this format:
+
+```markdown
+| Service | SKU | Region | Unit Price | Unit | Monthly Est. | Annual Est. |
+|---------|-----|--------|-----------|------|-------------|-------------|
+| Virtual Machines | Standard_D4s_v5 | East US | $0.192/hr | 1 Hour | $140.16 | $1,681.92 |
+```
+
+## Tips
+
+- Always clarify the **usage pattern** before estimating (24/7 vs. business hours vs. sporadic).
+- For **storage**, ask about expected data volume and access patterns.
+- For **databases**, ask about throughput requirements (RU/s, DTUs, or vCores).
+- For **serverless** services, ask about expected invocation count and duration.
+- Round to 2 decimal places for display.
+- Note that prices are in **USD** unless otherwise specified.