Claude Fable 5.1 vs Claude Sonnet 5: pricing and benchmarks
Claude Sonnet 5 is 80% cheaper on input tokens ($2.00 vs $10.00 per 1M). Claude Sonnet 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 costs $1,100 a month versus $5,500 for Claude Fable 5.1, 80% less. Claude Fable 5.1 scores 164.5 on the Epoch Capabilities Index vs 156.2 for Claude Sonnet 5.
Prices verified September 14, 2026.
Which should you choose?
Claude Fable 5.1 scores 164.5 on the Epoch Capabilities Index vs 156.2 for Claude Sonnet 5.
Claude Fable 5.1 scores 90.2% on FrontierMath (Tiers 1–3) vs 65.6% for Claude Sonnet 5.
Claude Sonnet 5 costs $4.00 per 1M tokens (3:1 input-to-output mix) vs $20.00 for Claude Fable 5.1, 80% less.
A trade-off: Claude Fable 5.1 is 8.3 ECI points more capable but costs 5.0x as much as Claude Sonnet 5.
Pricing and specs
| Claude Fable 5.1 | Claude Sonnet 5 | |
|---|---|---|
| Provider | Anthropic | Anthropic |
| API model ID | claude-fable-5-1 | claude-sonnet-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 | |
|---|---|---|
| Epoch Capabilities Index | 164.5 | 156.2 |
| GPQA Diamond· Science reasoning | — | 87.4% |
| FrontierMath (Tiers 1–3)· Advanced math | 90.2% | 65.6% |
| SimpleQA Verified· Factual accuracy | 70.8% | 33.7% |
| ARC-AGI-2· Abstract reasoning | 90.0% | — |
| DeepSWE· Coding | — | 53.8% |
| APEX-Agents· Agentic work | 47.4% | 32.5% |
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 | 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 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 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 78% 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 cost calculator
- $1,100/mo$0.02 / 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 Sonnet 5 pricing notes
Anthropic’s best combination of speed and intelligence.
- The $2 / $10 launch price is now the standard price; the planned rise to $3 / $15 will not happen.
- Cache writes cost $2.50 (5-minute cache) or $4 (1-hour cache) per 1M tokens.
- Uses Anthropic’s newer tokenizer, which produces roughly 30% more tokens for the same text.
Frequently asked questions
- Is Claude Fable 5.1 cheaper than Claude Sonnet 5?
- Claude Sonnet 5 is 80% cheaper on input tokens ($2.00 vs $10.00 per 1M). Claude Sonnet 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 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?
- Claude Fable 5.1 scores 164.5 on the Epoch Capabilities Index vs 156.2 for Claude Sonnet 5.
- 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 cost per 1M tokens?
- Claude Sonnet 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?
- Both offer a 1M-token context window.