Compare / Claude Sonnet 4.5 vs Claude Sonnet 5.5
Claude Sonnet 4.5 vs Claude Sonnet 5.5
Which is cheaper, which is more capable, and which does better at each kind of work, from 13 results on 3 sources that measured both models.
Of the 13 results both models have, the better value on each. Results whose reported ranges overlap are too close to call.
Results as of 5 November 2026 (catalogue release 2026-11-05-44c5fb63d296).
Claude Sonnet 4.5 or Claude Sonnet 5.5? The short answer
Pick Claude Sonnet 5.5: it scores higher (Intelligence Index 56.0 against 20.7) and costs less.
- Claude Sonnet 5.5 is cheaper: $4.00 against $6.00 per million tokens, 33% less.
- Claude Sonnet 5.5 scores higher on the Artificial Analysis Intelligence Index: 56.0 against 20.7.
- Claude Sonnet 5.5 is newer: released 28 Sep 2026, against 29 Sep 2025 for Claude Sonnet 4.5.
- On third-party benchmarks, on the results both models have: Claude Sonnet 5.5 does better for agents and tool use, reasoning and knowledge, writing and sticking to the facts.
Head to head
Every fact side by side
| Claude Sonnet 4.5 | Claude Sonnet 5.5 | |
|---|---|---|
| Price per million tokens | $3.00 in · $15.00 out | $2.00 in · $10.00 out |
| Blended (3 in : 1 out) | $6.00 | $4.00 |
| Cheapest host, blended | $6.00 (Amazon Bedrock) | $4.00 (Amazon Bedrock) |
| Cached input, per million | – | $0.20 cached input |
| Intelligence Index | 20.7 | 56.0 |
| Spring Prompt overall | – | 63 |
| Output speed, tokens a second | – | 137 |
| Context window | 1,000,000 tokens | 1,000,000 tokens |
| Released | 29 Sep 2025 | 28 Sep 2026 (newer) |
| Weights | Closed | Closed |
| Developer based in | the US | the US |
Prices are the developer's list price where we have read it, otherwise the typical host on OpenRouter; see every model's price. Intelligence and speed from Artificial Analysis.
Which is better for what
Each model's rank among the models on sale today, for each kind of work, from our own benchmarks and licensed sources. Further right is better; the better rank is in green.
From our research
Every shared result
Each model's best result on every measure both have, grouped by benchmark, with the setting that produced it. Under each measure, every model that benchmark has measured is a grey tick, best to the right, so you can see where the two sit in the field. The headline measures of each benchmark come first; the rest are under "Show all". Green marks the better value; where a source reports ranges that overlap, neither is marked.
| Measure | Claude Sonnet 4.5 | Claude Sonnet 5.5 |
|---|---|---|
| Arena (formerly LMArena) reported by Arena (formerly LMArena) · 3 results | ||
| Overall · TextArena rating, higher is better 56 · 39 of 387 measured | 1,457high-32k reasoning | 1,471xhigh reasoning |
| Overall · Text factualityArena rating, higher is better 61 · 24 of 163 measured | 1,449 | 1,470xhigh reasoning |
| Business, management and finance · TextArena rating, higher is better 51 · 46 of 380 measured | 1,461 | 1,464xhigh reasoning |
| Artificial Analysis reported by Artificial Analysis · 3 results | ||
| Artificial Analysis Intelligence Indexindex score, higher is better 107 · 2 of 249 measured | 20.7thinking reasoning | 56.0max reasoning |
| Humanity's Last Exam% of questions, higher is better 122 · 5 of 248 measured | 17.8%thinking reasoning | 55.0%max reasoning |
| Terminal-Bench 4.0% of tasks, higher is better 70 · 1 of 118 measured | 0.0%thinking reasoning | 63.6%max reasoning |
| SimpleQA Verified (Epoch AI) reported by SimpleQA Verified (Epoch AI) · 1 result | ||
| Correct answers% of questions, higher is better 58 · 33 of 76 measured | 30.7%thinking-59k reasoning | 46.5%max reasoning |
Show all 13 results (6 more)
| Measure | Claude Sonnet 4.5 | Claude Sonnet 5.5 |
|---|---|---|
| Arena (formerly LMArena) reported by Arena (formerly LMArena) · 4 results | ||
| Creative writing · TextArena rating, higher is better 27 · 34 of 385 measured | 1,454 | 1,447xhigh reasoning |
| Expert prompts · TextArena rating, higher is better 43 · 1 of 338 measured | 1,498high-32k reasoning | 1,556xhigh reasoning |
| Instruction following · TextArena rating, higher is better 38 · 15 of 387 measured | 1,464high-32k reasoning | 1,484xhigh reasoning |
| Writing, literature and language · TextArena rating, higher is better 38 · 27 of 386 measured | 1,454 | 1,461xhigh reasoning |
| Artificial Analysis reported by Artificial Analysis · 2 results | ||
| Long-context reasoning (AA-LCR)% of questions, higher is better 100 · 19 of 239 measured | 72.3%thinking reasoning | 82.7%max reasoning |
| SciCode% of problems, higher is better 69 · 4 of 119 measured | 45.7%thinking reasoning | 61.0%max reasoning |
Compare them with other models
Quick answers
Is Claude Sonnet 4.5 better than Claude Sonnet 5.5?
Pick Claude Sonnet 5.5: it scores higher (Intelligence Index 56.0 against 20.7) and costs less.
Which is cheaper, Claude Sonnet 4.5 or Claude Sonnet 5.5?
Claude Sonnet 5.5 is cheaper: $4.00 against $6.00 per million tokens, 33% less.
Which is better for agents and tool use, Claude Sonnet 4.5 or Claude Sonnet 5.5?
Claude Sonnet 5.5 ranks 1 of 160 models on sale for multi-step tasks with tools: support desks, coding agents, function calls, against 101 for Claude Sonnet 4.5.
Which is better for professional work, Claude Sonnet 4.5 or Claude Sonnet 5.5?
Claude Sonnet 5.5 ranks 1 of 51 models on sale for real tasks from banking, consulting and law, business documents and freelance projects, against 40 for Claude Sonnet 4.5.
Which is better for reasoning and knowledge, Claude Sonnet 4.5 or Claude Sonnet 5.5?
Claude Sonnet 5.5 ranks 2 of 188 models on sale for hard questions across science, maths and general knowledge, against 103 for Claude Sonnet 4.5.
Which is better for writing, Claude Sonnet 4.5 or Claude Sonnet 5.5?
Claude Sonnet 5.5 ranks 33 of 173 models on sale for what people prefer in blind comparisons, and judged writing quality, against 35 for Claude Sonnet 4.5.
Which is better for sticking to the facts, Claude Sonnet 4.5 or Claude Sonnet 5.5?
Claude Sonnet 5.5 ranks 43 of 143 models on sale for summarising without inventing things, and factual answers, against 95 for Claude Sonnet 4.5.
Run Claude Sonnet 4.5 and Claude Sonnet 5.5 on your own prompt.
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