Claude Opus 5.5 vs Claude Fable 5.1
Official Anthropic API prices and LMArena scores, checked 2026-10-28. Add up to 2 more models to compare 4.
Claude Opus 5.5 is cheaper and wins more LMArena tasks.
Claude Opus 5.5 is 2.5x cheaper on input and output. Claude Opus 5.5 scores 45 points higher for creative writing; Claude Fable 5.1 scores 28 points higher for reasoning and math. Across 7 shared LMArena tasks, Claude Opus 5.5 leads 6 to 1. A medium month (20M input + 5M output tokens) costs $180 on Claude Opus 5.5 and $450 on Claude Fable 5.1.
- Pick Claude Opus 5.5 if you want the lower bill ($180 vs $450 for a medium month), you care most about creative writing (+45), coding (+23) and roleplay (+23) or you reuse long prompts (cached input $0.20 vs $0.25).
- Pick Claude Fable 5.1 if you care most about reasoning and math (+28).
Medium: 20M input + 5M output tokens a month at list price (short-context rate, no caching or batch discounts).
Marked side is better: lower for prices, higher for context and scores. Bars are scaled to the larger of the two.
| Spec | Claude Opus 5.5 | Claude Fable 5.1 |
|---|---|---|
| Price per 1M tokens | ||
| Input | $4 | $10 |
| Cached input | $0.20 | $0.25 |
| Output | $20 | $50 |
| Blend 3:1 | $8 | $20 |
| Sample month, medium | $180 | $450 |
| Context | ||
| Context window | 1M tokens | 1M tokens |
| Quality (LMArena, out of 100) | ||
| Coding | 100/100 #1 of 24 | 77/100 #5 of 24 |
| Chat | 83/100 #2 of 26 | 72/100 #4 of 26 |
| Creative writing | 100/100 #1 of 26 | 55/100 #4 of 26 |
| Roleplay and characters | 41/100 #4 of 26 | 18/100 #9 of 26 |
| Reasoning and math | 67/100 #6 of 26 | 95/100 #2 of 26 |
| Vision | 84/100 #3 of 22 | 72/100 #7 of 22 |
| Long documents | Not ranked | 100/100 #1 of 9 |
| Cheap bulk and agents | 100/100 #1 of 22 | 83/100 #4 of 22 |
| Details | ||
| Provider | Anthropic | Anthropic |
| API model id | claude-opus-5.5 | claude-fable-5.1 |
| Notes | 5-minute cache writes $5. | Cache reads $0.25, 5-minute cache writes $12.50. |
| Sources | ||
| Last checked | 2026-10-28 | 2026-10-28 |
| Official pricing | Anthropic pricing | Anthropic pricing |
Plans from data checked hourly against each vendor's official pricing page. Vendors state limits in different units, so we quote them as published. Team and enterprise plans are per seat.
API prices in USD per 1M tokens from each provider's official pricing page. Blend 3:1 = (3 x input + output) / 4. Sample month = stated input and output tokens at the list price, no caching. Quality: relative score out of 100 on each LMArena leaderboard (100 = top model we price on that board, n/a = not ranked there), data licensed CC BY 4.0. See how we pick.
Where each one ranks on LMArena
Relative score out of 100 on each leaderboard (100 = the top model we price there), with the rank among the models from our API price table that appear on that board.
- Coding (Code Arena): Claude Opus 5.5 #1 of 24 (100/100), Claude Fable 5.1 #5 of 24 (77/100)
- Chat (Text Arena): Claude Opus 5.5 #2 of 26 (83/100), Claude Fable 5.1 #4 of 26 (72/100)
- Creative writing (Text Arena creative writing): Claude Opus 5.5 #1 of 26 (100/100), Claude Fable 5.1 #4 of 26 (55/100)
- Roleplay and characters (Text Arena multi-turn): Claude Opus 5.5 #4 of 26 (41/100), Claude Fable 5.1 #9 of 26 (18/100)
- Reasoning and math (Text Arena math): Claude Opus 5.5 #6 of 26 (67/100), Claude Fable 5.1 #2 of 26 (95/100)
- Vision (Vision Arena): Claude Opus 5.5 #3 of 22 (84/100), Claude Fable 5.1 #7 of 22 (72/100)
- Long documents (Document Arena): Claude Opus 5.5 not ranked, Claude Fable 5.1 #1 of 9 (100/100)
- Cheap bulk and agents (Agent Arena): Claude Opus 5.5 #1 of 22 (100/100), Claude Fable 5.1 #4 of 22 (83/100)
Pricing details from the official pages
Claude Opus 5.5 lists $4 input, $20 output, $0.20 cached input per 1M tokens on Anthropic pricing. Claude Fable 5.1 lists $10 input, $50 output, $0.25 cached input per 1M tokens on Anthropic pricing. Prices checked 2026-10-28.
- Claude Opus 5.5: 5-minute cache writes $5.
- Claude Fable 5.1: Cache reads $0.25, 5-minute cache writes $12.50.
Sample monthly bill at list price, no caching: Light (2M input + 0.5M output tokens): $18 vs $45. Medium (20M input + 5M output tokens): $180 vs $450. Heavy (200M input + 50M output tokens): $1,800 vs $4,500.
FAQ
Is Claude Opus 5.5 cheaper than Claude Fable 5.1?
Claude Opus 5.5 costs $4 input and $20 output per 1M tokens; Claude Fable 5.1 costs $10 and $50. For a medium month (20M input + 5M output tokens) Claude Opus 5.5 is cheaper: $180 vs $450.
Which is better for coding, Claude Opus 5.5 or Claude Fable 5.1?
On LMArena's Code Arena Claude Opus 5.5 scores 100/100 (#1 of 24) and Claude Fable 5.1 77/100 (#5 of 24), so Claude Opus 5.5 is ahead by 23 points.
Which has the bigger context window?
Claude Opus 5.5: 1M tokens. Claude Fable 5.1: 1M tokens. Both list the same window.
How much do Claude Opus 5.5 and Claude Fable 5.1 cost per month?
Light (2M input + 0.5M output tokens): $18 vs $45. Medium (20M input + 5M output tokens): $180 vs $450. Heavy (200M input + 50M output tokens): $1,800 vs $4,500. Pick your own token counts in the plan vs API calculator.
Where do these numbers come from?
Prices come from each provider's official pricing page, checked daily. Quality is the relative score on the LMArena leaderboard dataset, licensed CC BY 4.0. Where a model is not ranked we show n/a.
Sources
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