Claude Fable 5.1 vs Claude Sonnet 5.5: pricing and benchmarks
Claude Sonnet 5.5 is 80% cheaper on input tokens ($2.00 vs $10.00 per 1M). Claude Sonnet 5.5 is 80% cheaper on output tokens ($10.00 vs $50.00 per 1M). On our document Q&A workload (50,000 questions a month), Claude Sonnet 5.5 costs $1,100 a month versus $5,500 for Claude Fable 5.1, 80% less. Roughly tied. Claude Fable 5.1 scores 164.7 and Claude Sonnet 5.5 scores 164.4 on the Epoch Capabilities Index, and their confidence intervals overlap.
Which should you choose?
Roughly tied. Claude Fable 5.1 scores 164.7 and Claude Sonnet 5.5 scores 164.4 on the Epoch Capabilities Index, and their confidence intervals overlap.
About even on FrontierMath (Tiers 1–3): 90.2% for Claude Fable 5.1 and 88.8% for Claude Sonnet 5.5.
Claude Sonnet 5.5 costs $4.00 per 1M tokens (3:1 input-to-output mix) vs $20.00 for Claude Fable 5.1, 80% less.
Claude Sonnet 5.5 delivers statistically similar overall capability for 80% less.
Pricing and specs
| Claude Fable 5.1 | Claude Sonnet 5.5 | |
|---|---|---|
| Provider | Anthropic | Anthropic |
| API model ID | claude-fable-5-1 | claude-sonnet-5-5 |
| Input / 1M tokens | $10.00 | $2.00 |
| Cached input / 1M tokens | $0.25 | $0.20 |
| Output / 1M tokens | $50.00 | $10.00 |
| Long-context rates | — | — |
| Context window | 1M tokens | 1M tokens |
| Max output | 128K tokens | 128K tokens |
| Batch discount | 50% off | 50% off |
Benchmarks
| Claude Fable 5.1 | Claude Sonnet 5.5 | |
|---|---|---|
| Epoch Capabilities Index | 164.7 | 164.4 |
| GPQA Diamond· Science reasoning | — | 95.6% |
| FrontierMath (Tiers 1–3)· Advanced math | 90.2% | 88.8% |
| SimpleQA Verified· Factual accuracy | 70.8% | 46.5% |
| ARC-AGI-2· Abstract reasoning | 90.0% | — |
| DeepSWE· Coding | — | — |
| APEX-Agents· Agentic work | 68.6% | 75.5% |
Source: Epoch AI, best recorded result per model (CC BY 4.0). A dash means no published score. See all benchmarks
Monthly cost for real workloads
| Workload | Claude Fable 5.1 | Claude Sonnet 5.5 | Difference |
|---|---|---|---|
Support chatbot 100,000 replies a month, ~1,500 input tokens (system prompt + history) and ~400 output tokens each. | $3,500 | $700.00 | Claude Sonnet 5.5 80% cheaper |
Document Q&A (RAG) 50,000 questions a month with ~8,000 tokens of retrieved context and ~600 output tokens each. | $5,500 | $1,100 | Claude Sonnet 5.5 80% cheaper |
Coding agent 10,000 agent steps a month, ~40,000 input tokens each (70% read from the prompt cache) and ~2,000 output tokens. | $2,270 | $496.00 | Claude Sonnet 5.5 78% cheaper |
Cached chatbot The same 100,000-reply support chatbot, but 60% of each prompt (system prompt + conversation history) is served from the prompt cache. | $2,623 | $538.00 | Claude Sonnet 5.5 79% cheaper |
Meeting notes 10,000 meetings a month summarized from ~12,000-token transcripts, ~1,000 output tokens each. | $1,700 | $340.00 | Claude Sonnet 5.5 80% cheaper |
Bulk translation 200,000 short translations a month, ~800 input and ~800 output tokens each. | $9,600 | $1,920 | Claude Sonnet 5.5 80% cheaper |
Content moderation 1,000,000 classifications a month, ~400 input tokens and ~80 output tokens each. | $8,000 | $1,600 | Claude Sonnet 5.5 80% cheaper |
Article drafting 300 long-form articles a month written from a ~4,000-token brief and outline, ~5,000 output tokens each. | $87.00 | $17.40 | Claude Sonnet 5.5 80% cheaper |
Code review bot 30,000 pull-request reviews a month, ~5,000 input tokens each (30% cached repository context) and ~700 output tokens. | $2,111 | $429.00 | Claude Sonnet 5.5 80% cheaper |
Invoice extraction 100,000 documents a month parsed into structured JSON, ~1,200 input and ~250 output tokens each. | $2,450 | $490.00 | Claude Sonnet 5.5 80% cheaper |
Estimates use standard list prices and ignore cache-write surcharges. Different tokenizers can count the same text differently, so test with your own prompts.
Claude Fable 5.1 vs Claude Sonnet 5.5 cost calculator
- $1,100/mo$0.02 / req
- Claude Fable 5.1Anthropic$5,500/mo$0.11 / req
Standard-tier list prices. Long-context rates apply automatically where the provider publishes a threshold. Excludes cache-write surcharges, taxes, batch and volume discounts.
Claude Fable 5.1 pricing notes
Anthropic’s previous Fable model for demanding reasoning and long-horizon agentic work.
- Cache hits cost 2.5% of the base input price, versus 10% on other Claude models.
- Cache writes cost $12.50 (5-minute cache) or $20 (1-hour cache) per 1M tokens.
- Uses Anthropic’s newer tokenizer, which produces roughly 30% more tokens for the same text.
- US-only inference (inference_geo: "us") costs 1.1x.
Claude Sonnet 5.5 pricing notes
Anthropic’s fast mid-tier model, successor to Claude Sonnet 5 at the same price.
- Cache writes cost $2.50 (5-minute cache) or $4 (1-hour cache) per 1M tokens.
- US-only inference (inference_geo: "us") costs 1.1x.
Frequently asked questions
- Is Claude Fable 5.1 cheaper than Claude Sonnet 5.5?
- Claude Sonnet 5.5 is 80% cheaper on input tokens ($2.00 vs $10.00 per 1M). Claude Sonnet 5.5 is 80% cheaper on output tokens ($10.00 vs $50.00 per 1M). On our document Q&A workload (50,000 questions a month), Claude Sonnet 5.5 costs $1,100 a month versus $5,500 for Claude Fable 5.1, 80% less.
- Which is more capable, Claude Fable 5.1 or Claude Sonnet 5.5?
- Roughly tied. Claude Fable 5.1 scores 164.7 and Claude Sonnet 5.5 scores 164.4 on the Epoch Capabilities Index, and their confidence intervals overlap.
- How much does Claude Fable 5.1 cost per 1M tokens?
- Claude Fable 5.1 costs $10.00 per 1M input tokens and $50.00 per 1M output tokens, and $0.25 per 1M cached input tokens on Anthropic’s standard tier.
- How much does Claude Sonnet 5.5 cost per 1M tokens?
- Claude Sonnet 5.5 costs $2.00 per 1M input tokens and $10.00 per 1M output tokens, and $0.20 per 1M cached input tokens on Anthropic’s standard tier.
- Which has the larger context window, Claude Fable 5.1 or Claude Sonnet 5.5?
- Both offer a 1M-token context window.