Claude Fable 5.1 vs Gemini 4 Carbon: pricing and benchmarks
Gemini 4 Carbon is 80% cheaper on input tokens ($2.00 vs $10.00 per 1M). Gemini 4 Carbon is 80% cheaper on output tokens ($10.00 vs $50.00 per 1M). On our document Q&A workload (50,000 questions a month), Gemini 4 Carbon costs $1,100 a month versus $5,500 for Claude Fable 5.1, 80% less. Epoch AI has not published a capability index score for Gemini 4 Carbon yet.
Which should you choose?
Epoch AI has not published a capability index score for Gemini 4 Carbon yet.
Gemini 4 Carbon costs $4.00 per 1M tokens (3:1 input-to-output mix) vs $20.00 for Claude Fable 5.1, 80% less.
Pricing and specs
| Claude Fable 5.1 | Gemini 4 Carbon | |
|---|---|---|
| Provider | Anthropic | |
| API model ID | claude-fable-5-1 | gemini-4-carbon |
| Input / 1M tokens | $10.00 | $2.00 |
| Cached input / 1M tokens | $0.25 | $0.10 |
| Output / 1M tokens | $50.00 | $10.00 |
| Long-context rates | — | — |
| Context window | 1M tokens | 1.05M tokens |
| Max output | 128K tokens | 66K tokens |
| Batch discount | 50% off | 50% off |
Benchmarks
| Claude Fable 5.1 | Gemini 4 Carbon | |
|---|---|---|
| Epoch Capabilities Index | 164.7 | — |
| 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 | 68.6% | — |
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 | Gemini 4 Carbon | Difference |
|---|---|---|---|
Support chatbot 100,000 replies a month, ~1,500 input tokens (system prompt + history) and ~400 output tokens each. | $3,500 | $700.00 | Gemini 4 Carbon 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 | Gemini 4 Carbon 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 | $468.00 | Gemini 4 Carbon 79% 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 | $529.00 | Gemini 4 Carbon 80% cheaper |
Meeting notes 10,000 meetings a month summarized from ~12,000-token transcripts, ~1,000 output tokens each. | $1,700 | $340.00 | Gemini 4 Carbon 80% cheaper |
Bulk translation 200,000 short translations a month, ~800 input and ~800 output tokens each. | $9,600 | $1,920 | Gemini 4 Carbon 80% cheaper |
Content moderation 1,000,000 classifications a month, ~400 input tokens and ~80 output tokens each. | $8,000 | $1,600 | Gemini 4 Carbon 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 | Gemini 4 Carbon 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 | $424.50 | Gemini 4 Carbon 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 | Gemini 4 Carbon 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 Gemini 4 Carbon 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.
Gemini 4 Carbon pricing notes
Google’s most capable reasoning model, for sustained agentic coding, multimodal knowledge work and scientific reasoning.
- Introductory price through November 30, 2026. From December 1, 2026: $4 input, $0.20 cached, $20 output per 1M tokens.
- Not available on the Gemini API free tier.
- Output price includes thinking tokens.
- Max output is 65,536 tokens by default and up to 1,048,576 with long decode.
- Implicit caching only; explicit context caching is not supported.
- Priority inference costs 1.8x the standard rate.
Frequently asked questions
- Is Claude Fable 5.1 cheaper than Gemini 4 Carbon?
- Gemini 4 Carbon is 80% cheaper on input tokens ($2.00 vs $10.00 per 1M). Gemini 4 Carbon is 80% cheaper on output tokens ($10.00 vs $50.00 per 1M). On our document Q&A workload (50,000 questions a month), Gemini 4 Carbon costs $1,100 a month versus $5,500 for Claude Fable 5.1, 80% less.
- Which is more capable, Claude Fable 5.1 or Gemini 4 Carbon?
- Epoch AI has not published a capability index score for Gemini 4 Carbon 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 Gemini 4 Carbon cost per 1M tokens?
- Gemini 4 Carbon costs $2.00 per 1M input tokens and $10.00 per 1M output tokens, and $0.10 per 1M cached input tokens on Google’s standard tier.
- Which has the larger context window, Claude Fable 5.1 or Gemini 4 Carbon?
- Gemini 4 Carbon has the larger context window: 1.05M tokens versus 1M for Claude Fable 5.1.