Claude Fable 5.1 vs Claude Opus 5.5: pricing and benchmarks
Claude Opus 5.5 is 60% cheaper on input tokens ($4.00 vs $10.00 per 1M). Claude Opus 5.5 is 60% cheaper on output tokens ($20.00 vs $50.00 per 1M). On our document Q&A workload (50,000 questions a month), Claude Opus 5.5 costs $2,200 a month versus $5,500 for Claude Fable 5.1, 60% less. Epoch AI has not published a capability index score for Claude Opus 5.5 yet.
Prices verified September 26, 2026.
Which should you choose?
Epoch AI has not published a capability index score for Claude Opus 5.5 yet.
Claude Opus 5.5 costs $8.00 per 1M tokens (3:1 input-to-output mix) vs $20.00 for Claude Fable 5.1, 60% less.
Pricing and specs
| Claude Fable 5.1 | Claude Opus 5.5 | |
|---|---|---|
| Provider | Anthropic | Anthropic |
| API model ID | claude-fable-5-1 | claude-opus-5-5 |
| Input / 1M tokens | $10.00 | $4.00 |
| Cached input / 1M tokens | $0.25 | $0.20 |
| Output / 1M tokens | $50.00 | $20.00 |
| 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 Opus 5.5 | |
|---|---|---|
| Epoch Capabilities Index | 164.5 | — |
| GPQA Diamond· Science reasoning | — | — |
| FrontierMath (Tiers 1–3)· Advanced math | 90.2% | — |
| SimpleQA Verified· Factual accuracy | 70.8% | — |
| ARC-AGI-2· Abstract reasoning | 90.0% | — |
| DeepSWE· Coding | — | — |
| APEX-Agents· Agentic work | 47.4% | — |
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 Opus 5.5 | Difference |
|---|---|---|---|
Support chatbot 100,000 replies a month, ~1,500 input tokens (system prompt + history) and ~400 output tokens each. | $3,500 | $1,400 | Claude Opus 5.5 60% cheaper |
Document Q&A (RAG) 50,000 questions a month with ~8,000 tokens of retrieved context and ~600 output tokens each. | $5,500 | $2,200 | Claude Opus 5.5 60% 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 | $936.00 | Claude Opus 5.5 59% 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 Opus 5.5 cost calculator
- $2,200/mo$0.04 / request
- Claude Fable 5.1Anthropic$5,500/mo$0.11 / request
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 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 Opus 5.5 pricing notes
Anthropic’s recommended default model for most workloads, with adaptive thinking always on.
- Cache reads cost 5% of the input price, against 10% on Claude Opus 5 and Sonnet 5.
- Cache writes cost $5 (5-minute cache) or $8 (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 Opus 5.5?
- Claude Opus 5.5 is 60% cheaper on input tokens ($4.00 vs $10.00 per 1M). Claude Opus 5.5 is 60% cheaper on output tokens ($20.00 vs $50.00 per 1M). On our document Q&A workload (50,000 questions a month), Claude Opus 5.5 costs $2,200 a month versus $5,500 for Claude Fable 5.1, 60% less.
- Which is more capable, Claude Fable 5.1 or Claude Opus 5.5?
- Epoch AI has not published a capability index score for Claude Opus 5.5 yet.
- 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 Opus 5.5 cost per 1M tokens?
- Claude Opus 5.5 costs $4.00 per 1M input tokens and $20.00 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 Opus 5.5?
- Both offer a 1M-token context window.