Direct answer: Azure Cosmos DB's core cost is RU/s (throughput) + storage + regions/multi-write + backup. At official list prices on 8 November 2026 (US East, USD, excluding tax/discounts): standard provisioned throughput $0.008/hour per 100 RU/s (about $5.84/month per 100 RU/s), storage $0.25/GB-month; multi-region writes (multi-master) $0.016/hour per 100 RU/s (about $11.68/month per 100); serverless $0.25 per million RU + storage $0.25/GB-month; autoscale $0.012/hour per 100 RU/s (billed at 10-100% of max RU/s), plus potentially an entry price. Free tier includes 1,000 RU/s + 25 GB/month (one account per subscription). Decision rules: serverless fits sparse workloads with average utilization below about 9% of a provisioned tier; autoscale fits variable workloads with average utilization below about 66.7% of the max; steady high utilization is cheapest on standard provisioned.
This guide is for application/platform/data teams and procurement/FinOps using Cosmos DB. It explains RU/s, autoscale, serverless, multi-region writes, storage, backup/PITR, dedicated gateway and a 90-day optimization checklist. Prices come from the Azure Cosmos DB pricing page and Azure Retail Prices API (eastus, 8 November 2026). Official price facts, editorial calculations and exclusions are kept separate. This is not procurement advice.
(1) Watch average utilization first: serverless costs about 11x more per RU, so it is cheaper only below about 9% of a provisioned tier; autoscale costs 1.5x standard per RU, so it is cheaper only below about 66.7% of the max. (2) Storage, multi-region, backup, dedicated gateway and egress all add cost—do not model RU/s alone. (3) Free tier's 1,000 RU/s + 25 GB is for development/small workloads; production needs a bill-based model.
Billing basis: RU/s, storage, regions and multi-write
Cosmos DB abstracts compute/memory/IO into RU (Request Unit) and bills per RU/s. Standard provisioned throughput charges for provisioned RU/s whether used or not; autoscale sets a max RU/s and bills at 10-100% of the hourly max actually used; serverless bills actual RU consumed with no provisioned throughput. Storage is GB-month; multi-region deployments charge RU/s and storage in every region; multi-region writes (multi-master) cost about 2x single-write RU/s; cross-region traffic adds egress/replication. Backup/PITR, dedicated gateway and analytical storage are extra.
| Item | Price (USD) | Note |
|---|---|---|
| Standard provisioned | 0.008/hour/100 RU/s (about 5.84/month/100) | Provisioned RU/s, regardless of use |
| Autoscale | 0.012/hour/100 RU/s (about 8.76/month/100) | 10-100% of max RU/s; entry price extra |
| Serverless | 0.25/million RU | Actual RU; no provisioned throughput |
| Storage | 0.25/GB-month | Transactional+analytical data/index/backup; per region |
| Multi-region writes | 0.016/hour/100 RU/s (about 11.68/month/100) | About 2x single-write; storage per region |
| Free tier | 1,000 RU/s + 25 GB/month | One account per subscription; not for serverless |
Sources: Azure Cosmos DB pricing page and Azure Retail Prices API (eastus, 8 November 2026). Monthly prices converted at 730 hours; entry price/region/currency/discounts follow the official page and bill.
TCO scenarios: 1,000 / 10,000 RU/s and 10 GB / 1 TB
Standard provisioned: 1,000 RU/s + 10 GB = 10×5.84 + 10×0.25 = $60.90/month; 10,000 RU/s + 1 TB = 100×5.84 + 1,024×0.25 = $840.00/month. Multi-region writes 10,000 RU/s + 1 TB = 100×11.68 + 256 = $1,424.00/month (single-region storage; multi-region adds per-region storage). Serverless: 50M RU + 10 GB = 12.5 + 2.5 = $15.00/month; 500M RU + 1 TB = 125 + 256 = $381.00/month. These are throughput+storage only, excluding backup/gateway/egress/tax/discounts.
| Scenario | Throughput | Storage | Total/month |
|---|---|---|---|
| Standard 1,000 RU/s + 10 GB | 58.40 | 2.50 | 60.90 |
| Standard 10,000 RU/s + 1 TB | 584.00 | 256.00 | 840.00 |
| Multi-write 10,000 RU/s + 1 TB | 1,168.00 | 256.00 | 1,424.00 |
| Serverless 50M RU + 10 GB | 12.50 | 2.50 | 15.00 |
| Serverless 500M RU + 1 TB | 125.00 | 256.00 | 381.00 |
Editorial calculation: standard = RU/s/100 × 5.84; multi-write = RU/s/100 × 11.68; serverless = million RU × 0.25; storage = GB × 0.25 (1 TB = 1,024 GB). Excludes multi-region storage/egress, autoscale entry, backup/PITR, dedicated gateway, tax and discounts.
Break-even: serverless vs standard, autoscale vs standard
Serverless's per-RU price is about 11x standard provisioned ($0.25/million vs about $0.0225/million), so it is cheaper only when average RU/s utilization is below about 9% of the provisioned tier; for 1,000 RU/s, break-even is about 90 RU/s average. Autoscale's per-RU price is 1.5x standard (0.012 vs 0.008), so it is cheaper when average utilization is below about 66.7% of the max; above that, standard provisioned is cheaper. This rule is more reliable than "autoscale always saves".
| Comparison | Price relationship | Break-even |
|---|---|---|
| Serverless vs standard | 0.25/million RU vs about 0.0225/million | Average utilization below about 9% |
| Autoscale vs standard | 0.012 vs 0.008/100 RU/s-hour | Average utilization below about 66.7% of max |
| Multi-write vs single-write | About 2x RU/s price | Only pay when multi-write is required |
Editorial calculation: standard 100 RU/s-month = 100 × 2,592,000 RU = 259.2M RU, cost $5.84, about $0.0225/million RU; serverless $0.25/million is about 11.1x; 1/11.1 ≈ 9%. Autoscale 0.008/0.012 ≈ 66.7%. Excludes entry price/storage/regions/tax/discounts.
Hidden/add-on costs: backup, gateway, analytics, egress
Beyond RU/s and storage: continuous backup/PITR (30 days $0.2/GB-month; restore $0.15/GB; on-demand $0.1/GB; 7-day backup $0); dedicated gateway (D2s from $0.19/hour, about $139/month; D4s $0.38/hour, etc.); analytical storage ($0.03/GB-month + read $0.005/10K, write $0.05/10K); cross-region egress/replication; multi-region storage (charged per region). These can materially change TCO for large data, multi-region or compliance workloads.
| Add-on | Price (USD) | Caveat |
|---|---|---|
| PITR continuous backup 30 days | 0.2/GB-month; restore 0.15/GB | 7-day backup 0; on-demand 0.1/GB |
| Dedicated gateway D2s | 0.19/hour (about 139/month) | D4s 0.38/hour; size as needed |
| Analytical storage | 0.03/GB-month; read 0.005/10K, write 0.05/10K | Separate from transactional storage |
| Multi-region storage | 0.25/GB-month/region | Charged in every region |
| Cross-region egress | Azure data transfer rates | Replication/read traffic |
Sources: Azure Cosmos DB pricing page and Azure Retail Prices API (eastus, 8 November 2026). Editorial summary; availability/regions/discounts follow the official page and bill.
How to choose: serverless, autoscale, standard provisioned
Choose by average/peak ratio and predictability: development/test/sparse/low-traffic → serverless; highly variable traffic with high peaks but low average (<66.7% of max) → autoscale; steady high-utilization production → standard provisioned. Use multi-region writes only when multi-master writes are truly required; multi-region reads/DR need separate storage/egress math. Finally, validate RU consumption with the Cosmos DB capacity planner/monitoring instead of guessing RU/s.
| Scenario | Prefer | Check first |
|---|---|---|
| Development/test/sparse traffic | Serverless | Average RU/s, serverless limits |
| Variable, high peak | Autoscale | Max RU/s, average/peak ratio |
| Steady high utilization | Standard provisioned | Actual RU/s, reservations |
| Multi-region writes | Multi-master | 2x RU/s, regional storage/egress |
| Multi-region reads/DR | Single-write + multi-read | Per-region storage, replication traffic |
| Analytics/BI | Analytical storage | Storage/read-write rates |
| Compliance/PITR | Continuous backup | 30/7-day retention, restore fees |
Editorial selection framework, not a vendor recommendation; RU/s/regions/backup/compliance follow the business and official documentation.
90-day optimization checklist
Use the first 90 days to establish where RU goes, peak/average, storage/indexes and backup/multi-region. The order is monitor, partitioning/indexing, mode (serverless/autoscale/standard), multi-region/backup, reservations/discounts, review. The most common waste: provisioning for peak all year, poor partitioning/indexing inflating RU, ignoring serverless limits, duplicated multi-region storage and excessive backup retention.
| Phase | Action | Output |
|---|---|---|
| Weeks 1-2 | Pull RU/storage/region/backup bills and monitoring | Cost baseline, top containers |
| Weeks 2-4 | Review average/peak RU, hot partitions, indexes | RU optimization list |
| Weeks 4-6 | Choose serverless/autoscale/standard by utilization | Mode plan |
| Weeks 6-8 | Check multi-region/multi-write/backup/PITR necessity | Region/backup plan |
| Weeks 8-10 | Evaluate reservations/discounts/dedicated gateway | Procurement recommendation |
| Weeks 10-12 | Set budget alerts, monthly review | Alerts, review process |
Editorial optimization advice, not an official template; RU/s/regions/backup/compliance follow enterprise standards and official documentation.
FAQ
How is Cosmos DB billed?
By RU/s (throughput), storage, regions/multi-write, backup/gateway/egress. Standard provisioned 0.008/hour/100 RU/s (about 5.84/month/100), storage 0.25/GB-month; autoscale 0.012/hour/100; serverless 0.25/million RU; multi-region writes 0.016/hour/100.
Is serverless always cheaper?
No. Serverless's per-RU price is about 11x standard provisioned; it is cheaper only below about 9% average utilization of a provisioned tier. Steady high utilization is cheaper on standard provisioned.
When does autoscale save?
Autoscale's per-RU price is 1.5x standard; it is cheaper when average utilization is below about 66.7% of the max. If you consistently run at the max, standard provisioned is cheaper.
How much is 1,000 RU/s per month?
Standard provisioned about $58.40/month (10×5.84), plus 10 GB storage about $2.50, total about $60.90; excluding backup/gateway/egress/tax/discounts.
How much is 10,000 RU/s + 1 TB?
Standard provisioned about $584 + $256 = $840/month; multi-region writes about $1,168 + $256 = $1,424/month (single-region storage); multi-region adds per-region storage/egress.
Is free tier enough for production?
Free tier gives 1,000 RU/s + 25 GB/month, one account per subscription; it fits development/small workloads. Production should model actual RU/storage/regions; do not assume the free allowance is enough.
How much more do multi-region writes cost?
Multi-region writes cost about 2x single-write RU/s (0.016 vs 0.008/hour/100), and storage is charged in every region; cross-region egress/replication also applies. Use only when multi-master writes are required.
How is backup/PITR billed?
Continuous backup 30 days about $0.2/GB-month, restore $0.15/GB; on-demand backup $0.1/GB; 7-day backup $0. Longer retention/larger data costs more; set retention by RPO.
Research method and limitations
This article separates "official price facts" from "editorial calculations." Standard/multi-write/serverless/storage/free-tier/PITR/dedicated-gateway/analytical-storage prices come from the Azure Cosmos DB pricing page and Azure Retail Prices API (eastus, 8 November 2026). TCO, break-even, selection framework and the 90-day checklist are editorial. Prices use 730 hours/month and 1 TB = 1,024 GB; the bill is authoritative.
Eight limitations: (1) only US East list prices, excluding tax/discounts/reservations; (2) the complete autoscale entry-price tiers are not modeled; (3) multi-region storage/egress/replication are excluded; (4) not all backup/PITR/gateway/analytical combinations are included; (5) assumes 1 TB = 1,024 GB; (6) no real RU/partition/index benchmark is included; (7) other APIs (PostgreSQL/vCore/MongoDB vCore/Garnet) are not covered; (8) prices/products change, so recheck the official page and bill before purchase.
Sources and basis
- Microsoft Azure, Azure Cosmos DB Pricing: azure.microsoft.com/en-us/pricing/details/cosmos-db. Standard/autoscale/serverless/storage/multi-write/free tier/PITR/gateway. Accessed 8 November 2026.
- Azure Retail Prices API (productName contains Cosmos DB, eastus): prices.azure.com/api/retail/prices. 0.008/0.012/0.016, 0.25/GB, 0.25/million RU, backup/gateway. Accessed 8 November 2026.
Data cut-off 8 November 2026; prices/availability follow the Azure official page and bill; this is not procurement, commercial or legal advice.