GPT-6 API Cost Calculator

Compare GPT-6 Sol vs Luna pricing per 1M tokens and estimate your monthly API spend in seconds. Free, no signup.

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GPT-6 API pricing table

Per 1M tokens. Snapshot — providers change prices, always verify on the official pricing page.

ModelInput / 1MCached input / 1MOutput / 1MBest for
GPT-6 Luna$0.10$0.025$0.50High-volume, cost-efficient workloads
GPT-6 Sol$2.00$0.50$8.00Flagship quality, complex reasoning

Prices last verified: September 26, 2026 · Source: OpenAI platform pricing (verify at platform.openai.com/docs/pricing)

GPT-6 Sol vs Luna vs Claude Opus 5.5

Same workload, very different bills. Luna wins on price by a mile; the flagships compete on quality.

ModelInput / 1MOutput / 1MRelative cost
GPT-6 Luna$0.10$0.50Baseline — cheapest
GPT-6 Sol$2.00$8.00~16–20× Luna
Claude Opus 5.5$4.00$20.00~40× Luna

Rule of thumb: if Luna's quality clears your bar, nothing else comes close on price. Pay for Sol/Opus only when the task genuinely needs frontier reasoning.

How GPT-6 API pricing works

OpenAI bills GPT-6 by the token, split into input and output. Input is everything you send — system prompt, conversation history, the user message, tool definitions. Output is everything the model generates, including hidden reasoning tokens. Output is priced higher because generation is the expensive part.

The input/output ratio decides your bill

A RAG chatbot with long retrieved context might run 10:1 input-to-output. A code generator might run 1:3. Two apps with the same request count can differ 10× in cost. Before optimizing the model choice, measure your real token split — most developers overestimate output and underestimate how much history they resend every turn.

Caching is the biggest lever

If your system prompt and context repeat across requests, cached input pricing (a fraction of standard input rates) applies to the repeated prefix. Apps with stable system prompts routinely cut input spend 50–80% with caching. In the calculator above, move the cached-input slider to see the effect on your workload.

When to pick which model

Luna is the price-performance pick: classification, extraction, simple chat, bulk processing. Sol earns its premium on hard reasoning — math, complex code, agentic multi-step tasks where a weaker model's mistakes cost more than the price gap. Prototype on Sol, then test whether Luna holds quality on your evals; most teams are surprised how often it does.

Frequently asked questions

Quick answers to the pricing questions developers actually search for.

How much does GPT-6 cost per 1M tokens?
GPT-6 Luna costs $0.10 per 1M input tokens and $0.50 per 1M output tokens. GPT-6 Sol is the flagship tier and priced higher. Prices change — always check OpenAI's official pricing page.
GPT-6 Sol vs Luna: which is cheaper?
Luna is dramatically cheaper per token. Choose Luna for high-volume, simpler tasks; choose Sol when you need maximum reasoning quality and the higher price is justified by better results.
What is cached input pricing for GPT-6?
Cached inputs (repeated prompt prefixes) are billed at a discounted rate, typically a fraction of standard input pricing. If your app reuses system prompts, caching can cut input costs significantly.
How do I estimate my monthly GPT-6 API bill?
Multiply tokens per request by requests per month, split into input vs output, then apply the per-1M-token rates. Use the calculator at the top of this page — enter your numbers and it does the math instantly.
Is GPT-6 cheaper than Claude Opus 5.5?
GPT-6 Luna ($0.10/$0.50 per 1M) is far cheaper than Claude Opus 5.5 ($4/$20 per 1M). They target different needs: Luna for cost-efficient scale, Opus 5.5 for frontier quality.
What counts as input vs output tokens?
Input tokens are everything you send: system prompt, conversation history, user message, tools. Output tokens are what the model generates, including reasoning tokens. Output is almost always priced higher.
Does the Batch API change GPT-6 pricing?
OpenAI's Batch API has historically offered around 50% off for non-urgent workloads with 24-hour turnaround. Check the official pricing page for current batch discounts on GPT-6.
Where can I verify official GPT-6 pricing?
Always verify at platform.openai.com/docs/pricing — this page's numbers are a snapshot and providers change prices without notice.