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Claude Opus 5.5 vs Claude Sonnet 4.5

Claude Opus 5.5 leads the LLM Stats Score 59.7 to 32.1. Claude Sonnet 4.5 is 1.3x cheaper per token.

Anthropic · Anthropic · Updated for 2026

Which is better?

Claude Opus 5.5 leads the overall LLM Stats Score 59.7 to 32.1, ranking #1 overall.

On price, Claude Sonnet 4.5 is roughly 1.3x cheaper per token on a blended 3:1 input/output basis, which adds up quickly at production volume.

Claude Opus 5.5 also accepts a larger context window (1,000,000 input tokens), making it the stronger choice for long documents and large codebases.

Based on current LLM Stats indexes, shared benchmarks, pricing, and model metadata for 2026.

Choose Claude Opus 5.5

  • overall performance matters — it scores 59.7 and ranks #1 on LLM Stats
  • your work emphasizes reasoning and coding — it leads those capability indexes
  • you process long inputs — it offers a 1,000,000 token context window
  • you want the most recent training data — it shipped Sep 2026

Choose Claude Sonnet 4.5

  • cost matters — it's about 1.3x cheaper per token

At a glance

The differences that matter most.

Claude Opus 5.5
Anthropic
Claude Sonnet 4.5
Anthropic
Core performance indexes
LLM Stats Score
59.7
#1
32.1
#113
Reasoning
57.8
#1
31.3
#114
Coding
51.7
#1
21.5
#93
Agents
44.5
#2
17.2
#80
Cost, coverage & limits
Benchmark wins
—
—
Input price
$4.00 / M
$3.00 / M
Output price
$20.00 / M
$15.00 / M
Context window
1,000,000
200,000

Capability indexes

Additional strengths measured across groups of related public benchmarks

4 shared
Index
Claude Opus 5.5
Claude Sonnet 4.5
Math
42.5#5
25.0#116
Vision
42.8#1
10.7#122
Tool use
32.9#2
26.1#27
Multimodal
42.5#1
12.6#110
Conservative TrueSkill rating · higher is betterHow scores work

Individual benchmarks

31 reported for Claude Opus 5.5 · 9 for Claude Sonnet 4.5

No common benchmarks found

Claude Opus 5.5 and Claude Sonnet 4.5don't have any common benchmark datasets to compare. They may have been evaluated on different testing suites.

Human preference

Blind head-to-head votes and playground preference scores

Pricing Analysis

Price comparison per million tokens

Claude Sonnet 4.5 costs less

For input processing, Claude Opus 5.5 ($4.00/1M tokens) is 1.3x more expensive than Claude Sonnet 4.5 ($3.00/1M tokens).

For output processing, Claude Opus 5.5 ($20.00/1M tokens) is 1.3x more expensive than Claude Sonnet 4.5 ($15.00/1M tokens).

In conclusion, Claude Opus 5.5 is more expensive than Claude Sonnet 4.5.*

* Using a 3:1 ratio of input to output tokens

Lowest available price from all providers
Tue Sep 22 2026 • llm-stats.com
Anthropic
Claude Opus 5.5
Input tokens$4.00
Output tokens$20.00
Best providerAnthropic
Anthropic
Claude Sonnet 4.5
Input tokens$3.00
Output tokens$15.00
Best providerAnthropic
Notice missing or incorrect data?Start an Issue→

Context Window

Maximum input and output token capacity

Claude Opus 5.5 accepts 1,000,000 input tokens compared to Claude Sonnet 4.5's 200,000 tokens. Claude Opus 5.5 can generate longer responses up to 128,000 tokens, while Claude Sonnet 4.5 is limited to 64,000 tokens.

Anthropic
Claude Opus 5.5
Input1,000,000 tokens
Output128,000 tokens
Anthropic
Claude Sonnet 4.5
Input200,000 tokens
Output64,000 tokens
Tue Sep 22 2026 • llm-stats.com

Input capabilities

Documented input modalities across available providers

Both Claude Opus 5.5 and Claude Sonnet 4.5 support multimodal inputs.

They are both capable of processing various types of data, offering versatility in application.

Claude Opus 5.5

Text
Images
Audio
Video

Claude Sonnet 4.5

Text
Images
Audio
Video

License

Usage and distribution terms

Both models are licensed under proprietary licenses.

Both models have usage restrictions defined by their respective organizations.

Claude Opus 5.5

Proprietary

Closed source

Claude Sonnet 4.5

Proprietary

Closed source

Release Timeline

When each model was launched

Claude Opus 5.5 was released on 2026-09-22, while Claude Sonnet 4.5 was released on 2025-09-29.

Claude Opus 5.5 is 12 months newer than Claude Sonnet 4.5.

Claude Opus 5.5

Sep 22, 2026

0 days ago

11mo newer
Claude Sonnet 4.5

Sep 29, 2025

11 months ago

Knowledge Cutoff

When training data ends

Claude Opus 5.5 has a knowledge cutoff of 2026-06-01, while Claude Sonnet 4.5 has a cutoff of 2025-01-31.

Claude Opus 5.5 has more recent training data (up to 2026-06-01), making it potentially better informed about events through that date compared to Claude Sonnet 4.5 (2025-01-31).

Claude Opus 5.5

Jun 2026

1.4 yr newer
Claude Sonnet 4.5

Jan 2025

Provider Availability

Claude Opus 5.5 is available from Anthropic. Claude Sonnet 4.5 is available from Anthropic.

Claude Opus 5.5

anthropic logo
Anthropic
Input Price:Input: $4.00/1MOutput Price:Output: $20.00/1M

Claude Sonnet 4.5

anthropic logo
Anthropic
Input Price:Input: $3.00/1MOutput Price:Output: $15.00/1M
* Prices shown are per million tokens

Outputs Comparison

Notice missing or incorrect data?Start an Issue discussion→

Judge for yourself.

Run your own prompts against Claude Opus 5.5 and Claude Sonnet 4.5 side-by-side, then vote on the output you prefer.

Claude Opus 5.5
✓ Preferred
Claude Sonnet 4.5
Open in Playground

FAQ

Common questions about Claude Opus 5.5 vs Claude Sonnet 4.5.

Which is better, Claude Opus 5.5 or Claude Sonnet 4.5?

Claude Opus 5.5 leads the LLM Stats Score 59.7 to 32.1. Claude Opus 5.5 is made by Anthropic and Claude Sonnet 4.5 is made by Anthropic. The best choice depends on your use case — compare their capability indexes, individual benchmarks, pricing, and limits above.

How does Claude Opus 5.5 compare to Claude Sonnet 4.5 in benchmarks?

Claude Opus 5.5 scores BenchCAD (with Python tool): 96.2%, Global-MMLU: 94.3%, SWE-bench Multilingual: 93.9%, MILU: 93.1%, ArXivMath: 91.2%. Claude Sonnet 4.5 scores MMMLU: 89.1%, AIME 2025: 87.0%, TAU-bench Retail: 86.2%, GPQA: 83.4%, MMMUval: 77.8%.

Is Claude Opus 5.5 cheaper than Claude Sonnet 4.5?

Claude Sonnet 4.5 is 1.3x cheaper for input tokens. Claude Opus 5.5 costs $4.00/M input and $20.00/M output via anthropic. Claude Sonnet 4.5 costs $3.00/M input and $15.00/M output via anthropic.

What are the context window sizes for Claude Opus 5.5 and Claude Sonnet 4.5?

Claude Opus 5.5 supports 1.0M tokens and Claude Sonnet 4.5 supports 200K tokens. A larger context window lets you process longer documents, conversations, or codebases in a single request.

What are the main differences between Claude Opus 5.5 and Claude Sonnet 4.5?

Key differences include LLM Stats Score (59.7 vs 32.1), context window (1.0M vs 200K), input pricing ($4.00 vs $3.00/M). See the full comparison above for benchmark-by-benchmark results.

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