Estimate OpenAI GPT-5.6 API costs for Sol, Terra and Luna, including long-context rates, cache writes, cache reads and output pricing for production planning. Enter representative per-request token counts and the calculator applies OpenAI’s higher long-context matrix automatically above 272,000 input tokens.
Use token counts from a representative API response wherever possible. Pricing can change, so confirm material budgets against OpenAI’s official API pricing and the selected model page.
Estimate your OpenAI API cost
Pricing verified: 19 August 2026. Standard API rates in USD.
GPT-5.6 Luna · Short context · 1,000 requests
- Uncached input
- $0.20
- Cache writes
- $0.00
- Cache reads
- $0.00
- Output
- $0.60
- Average per request
- $0.0008
Planning estimate only. It excludes tools, storage, fine-tuning, regional charges, retries, taxes, contracted discounts and non-token fees.
Current OpenAI API rates used by this calculator
Rates are USD per million tokens for Standard API requests. A request with more than 272,000 total input tokens uses the long-context rates for the full request.
| Model and context | Input | Cache read | Cache write | Output |
|---|---|---|---|---|
| GPT-5.6 Sol – short | $5 | $0.50 | $6.25 | $30 |
| GPT-5.6 Sol – long | $10 | $1 | $12.50 | $45 |
| GPT-5.6 Terra – short | $2 | $0.20 | $2.50 | $12 |
| GPT-5.6 Terra – long | $4 | $0.40 | $5 | $18 |
| GPT-5.6 Luna – short | $0.20 | $0.02 | $0.25 | $1.20 |
| GPT-5.6 Luna – long | $0.40 | $0.04 | $0.50 | $1.80 |
“Long” means more than 272,000 input tokens in one request, not 272,000 tokens across all monthly requests. Cache-write rates equal 1.25 times the corresponding uncached-input rate.
How to estimate an OpenAI API bill
- Choose the exact model. Sol, Terra and Luna have different input, caching and output prices.
- Enter per-request token counts. Keep uncached input, cache creation, cache reads and output separate.
- Enter request volume. For a monthly forecast, use the number of calls expected in a typical month.
- Check the context notice. The calculator totals all input categories per request and switches the entire request to the published long-context matrix above 272,000 tokens.
- Reconcile with actual usage. Re-run the estimate when prompts, caching or models change.
Formula used
Total = requests × ((uncached input × input rate) + (cache writes × write rate) + (cache reads × cached rate) + (output × output rate)) / 1,000,000
Which GPT-5.6 model should you price?
- GPT-5.6 Sol is the frontier option for the hardest workloads. Price it when quality is more important than unit cost.
- GPT-5.6 Terra is the balanced option for production agents and general-purpose work.
- GPT-5.6 Luna is the cost-sensitive option for high-volume or simpler workloads.
Model choice should be based on your own quality, latency and reliability tests. A cheaper rate does not guarantee a lower end-to-end cost if a workflow needs more retries or tokens.
Frequently asked questions
Are ChatGPT subscriptions included?
No. ChatGPT plans and API usage are billed separately. This tool estimates API token charges only.
Why are cache writes separate from cached input?
Creating a reusable cache and reading from that cache have different rates. Combining them can materially understate a workload that frequently creates new cache entries.
Why might the final bill differ?
Retries, tool calls, hidden system or tool-schema tokens, model changes, storage, regional pricing, contract terms and taxes can all change the final invoice.
Compare providers with the Claude API cost calculator and Gemini API cost calculator, or visit the AI cost calculators hub.