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GPT-5.6 Luna API Cost Calculator

What GPT-5.6 Luna costs at $0.20 in and $1.20 out per million tokens, and what switching to GPT-6 Luna or Gemini Flash-Lite would change.

Updated · By Niraj Kumar · 6 sources

Each request

Count text inCount text in
tokens

System prompt, conversation history, documents and tool definitions are all resent on every call.

tokens

The visible answer.

Count tokens from a prompt or JSON payloadShow

Plain text, OpenAI Chat or Responses JSON, or Anthropic Messages JSON. A final assistant message or a response body counts as output. Counted in your browser; nothing is uploaded.

Loading the tokenizer…

Counts use OpenAI's o200k tokenizer, so they are exact for GPT-6 and GPT-5 models, plus a few tokens of message framing. Other providers' tokenizers count the same text differently and do not publish a conversion factor; Anthropic says Claude models from 4.7 on produce about 30% more tokens than earlier Claude models. For an exact count on another model, paste one of its API responses: the usage it reports is shown above.

tokens

Thinking tokens are billed as output. Leave at 0 for models or settings that do not reason.

Volume

PricePrice

30,000 requests over 30 days.

Discounts

%
0%100%

The share of input that repeats exactly at the start of every request, such as a fixed system prompt. The prompt caching calculator prices cache writes and expiry in detail.

Batch APIBatch API
Monthly cost$36.00$0.0012 a request on GPT-5.6 Luna
Per 1,000 requests
$1.20
Input
$18.00
Output
$18.00
Price rank
4th cheapest of 24
Cheapest listed model
Claude Haiku 5.5
$16.50 a month, $19.50 less
Output50%
  • Input50%
  • Output50%
Every model on this workload, per month3,000 tokens in, 500 out, 1,000 a day. Hover or focus a row for rates.
  1. 1Claude Haiku 5.5Anthropic$16.50
  2. 2GPT-6 LunaOpenAI$16.50
  3. 3Qwen3.8 FlashAlibaba$20.55
  4. 4GPT-5.6 LunaOpenAI$36.00
  5. 5DeepSeek V4.1 FlashDeepSeek$45.00
  6. 6Qwen3.7 PlusAlibaba$60.00
  7. 7Gemini 3.5 Flash-LiteGoogle$64.50
  8. 8Gemini 3.8 FlashGoogle$123.75
  9. 9Grok 4.3xAI$150.00
  10. 10Claude Haiku 4.5Anthropic$165.00
  11. 11DeepSeek V4 ProDeepSeek$178.20
  12. 12Grok 4.7xAI$270.00
  13. 13Qwen3.8 MaxAlibaba$270.00
  14. 14Claude Sonnet 5.5Anthropic$330.00
  15. 15Claude Sonnet 5Anthropic$330.00
  16. 16GPT-6.1 SolOpenAI$330.00
  17. 17GPT-6 SolOpenAI$330.00
  18. 18GPT-5.6 TerraOpenAI$360.00
  19. 19Gemini 3.1 ProGoogle$360.00
  20. 20Claude Opus 5.5Anthropic$660.00
  21. 21GPT-5.6 SolOpenAI$660.00
  22. 22Claude Opus 5Anthropic$825.00
  23. 23Claude Fable 5.1Anthropic$1,650
  24. 24GPT-6 AstraOpenAI$1,650

How the GPT-5.6 Luna API Cost Calculator works

As of October 13, 2026, GPT-5.6 Luna costs $0.20 per million input tokens and $1.20 per million output tokens, with cache hits at $0.02. A request costs its input tokens × the input rate ÷ 1,000,000 plus its output tokens × the output rate ÷ 1,000,000; multiply by requests for the monthly bill.

cost = (fresh input × input rate + cached input × cache rate + (output + reasoning) × output rate) ÷ 1,000,000

This page uses the same method as the LLM API Cost Calculator, which explains each term and assumption in full.

Worked example

A chat feature on GPT-5.6 Luna sending 3,000 input tokens and getting 500 back, 1,000 times a day.

  1. 1Input: 3,000 × $0.20 ÷ 1,000,000 = $0.0006
  2. 2Output: 500 × $1.20 ÷ 1,000,000 = $0.0006
  3. 3Per request: $0.0012
  4. 4Per month: $0.0012 × 1,000 × 30 = $36.00

$36.00 a month. Caching a fixed system prompt that makes up 80% of the input would bring it to about $23.04, and the batch API would halve either figure.

Frequently asked questions

How much does GPT-5.6 Luna cost per million tokens?

$0.20 per million input tokens and $1.20 per million output tokens at OpenAI's standard rate. Cache hits are $0.02 and cache writes $0.25. The batch API takes 50% off. Prompts over 272,000 tokens are billed at $0.40 input and $1.80 output for the whole request.

Should I move from GPT-5.6 Luna to GPT-6 Luna?

On price, GPT-6 Luna halves the input rate to $0.10 and cuts output from $1.20 to $0.50 per million tokens, so most workloads cost less than half as much. Both share the same 272,000-token long-context threshold and batch discount. Check output quality on a sample of your own traffic before switching.

How big a request can GPT-5.6 Luna take?

Up to 1.05 million tokens of context, input and output together, and up to 128,000 output tokens per response. That is roughly 790,000 words of English. The calculator warns when a request will not fit.

Sources

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