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Claude Mythos 5.1 API Pricing & Cost Calculator

Claude Mythos 5.1 keeps Mythos 5's $10.00 input / $50.00 output per 1M tokens and 1M context, but cached input falls from $1.00 to $0.25/1M — a quarter of the previous rate. That is the same change Anthropic made from Fable 5 to Fable 5.1, and the two 5.1 models now carry identical pricing. Anthropic lists a retirement date of 2027-09-01.

Anthropic plans to retire Claude Mythos 5.1 on 2027-09-01

Pricing below is still current. Worth factoring the retirement date into anything you are building on it long-term.

Still available from Anthropic: Claude Fable 5, Claude Mythos 5, Claude Fable 5.1

Input

$10.00

per 1M tokens

Output

$50.00

per 1M tokens

Context window

tokens

Listed here

2026-09

Model

≈ Estimated tokenizer·$10.00 in·$50.00 out (per 1M)

Quick start with a use case

Input tokens

Output tokens

Total cost per call$0.0350

Input$0.0100

Output$0.0250

Cost comparison

Standard

$0.0350

With Caching

$0.0301

Save 14% ↓

With Batch

Not supported

Cutting costs? Open models start at $0.28/1M

DeepSeek, Kimi & 200+ open models on Novita AI — often 5–20x cheaper than proprietary APIs for comparable tasks.

Try Novita AI

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Detailed pricing

Claude Mythos 5.1 pricing breakdown

All pricing dimensions including caching and batch discounts.

Type	Price (per 1M tokens)	Note
Input	$10.0000	Standard input tokens
Output	$50.0000	Generated output tokens
Cached input	$0.2500	Reused prompt content
Cache write	$12.5000	First-time cache deposit (Anthropic / Gemini style)

Cutting costs? Open models start at $0.28/1M

DeepSeek, Kimi & 200+ open models on Novita AI — often 5–20x cheaper than proprietary APIs for comparable tasks.

Try Novita AI

Affiliate link — we may earn a commission at no extra cost to you.

Last verified 2026-10-31 · Anthropic official pricing · ⚠️ Spotted a wrong price? Report in 30s →

How it compares

Claude Mythos 5.1 vs alternatives

Single-call cost (1000 input + 500 output tokens) ranked from cheapest.

Model	Per call	vs Mythos 5.1
Claude Mythos 5.1 Anthropic · this page	$0.0350	—
GPT-6 Luna OpenAI	$0.000350	−99%
Claude Haiku 5.5 Anthropic	$0.000350	−99%
DeepSeek V3.2 DeepSeek	$0.000480	−99%
GPT-5.6 Luna OpenAI	$0.000800	−98%
DeepSeek V4-Flash DeepSeek	$0.000900	−97%

Recommended use

When to choose Claude Mythos 5.1

Claude Mythos 5.1 shines for general-purpose tasks, complex multi-step reasoning, image and document understanding, and long documents and large codebases. Token counts are estimated within ~10-20% margin.

✓Context window of 1M tokens handles entire codebases or book-length documents.

✓Prompt caching available — significant savings for repeated system prompts.

✓Tool / function calling supported.

FAQ

Frequently asked questions

Claude Mythos 5.1 costs $10.00 per 1M input tokens and $50.00 per 1M output tokens. A typical chat call (1000 input + 500 output tokens) costs approximately $0.0350. Use the calculator above to estimate your specific use case.

Claude Mythos 5.1 supports a 1M token context window with a max output of 128,000 tokens.

Yes. Cached input is priced at $0.25 per 1M tokens — 98% cheaper than uncached input. This is especially valuable for repeated system prompts, long-context retrieval, and chat threads with shared history.

Yes, Claude Mythos 5.1 accepts image input. Vision token pricing is generally calculated based on image dimensions and folded into the input token count. Specific image-specific pricing varies — refer to Anthropic's official documentation.

Token counts for Claude Mythos 5.1 are estimated from character ratios (~10-20% margin). Cost calculations use prices verified on 2026-10-31. For final billing accuracy, always verify with Anthropic's usage dashboard.

Claude Mythos 5.1 does not currently support fine-tuning. Consider another model in the Anthropic family if fine-tuning is required.