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Claude Opus 5.5 vs Claude Sonnet 5.5

Claude Opus 5.5 and Claude Sonnet 5.5 are closely matched at 60.0 and 51.5 on the LLM Stats Score. Claude Sonnet 5.5 is 2.0x cheaper per token.

Anthropic · Anthropic · Updated for 2026

Which is better?

Claude Opus 5.5 and Claude Sonnet 5.5 are closely matched on the overall LLM Stats Score at 60.0 and 51.5.

In the 5 individual benchmarks reported for both models, Claude Opus 5.5 wins 4; this is a narrower head-to-head signal than the composite indexes.

On price, Claude Sonnet 5.5 is roughly 2.0x cheaper per token on a blended 3:1 input/output basis, which adds up quickly at production volume.

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

Choose Claude Opus 5.5

  • you value its reported benchmark strengths — it wins 4 of 5 exact shared results

Choose Claude Sonnet 5.5

  • cost matters — it's about 2.0x cheaper per token
  • you want the most recent training data — it shipped Sep 2026

At a glance

The differences that matter most.

Claude Opus 5.5
Anthropic
Claude Sonnet 5.5
Anthropic
Core performance indexes
LLM Stats Score
60.0
#1
51.5
#12
Reasoning
58.0
#1
49.7
#16
Coding
51.5
#1
42.6
#7
Agents
45.4
#2
39.3
#9
Cost, coverage & limits
Benchmark wins
4 of 5
1 of 5
Input price
$4.00 / M
$2.00 / M
Output price
$20.00 / M
$10.00 / M
Context window
1,000,000
1,000,000

Individual benchmarks

31 reported for Claude Opus 5.5 · 8 for Claude Sonnet 5.5

5 shared

Claude Opus 5.5 outperforms in 4 benchmarks (AA-Briefcase v1.1, CursorBench 4.0, FrontierCode 1.1, GDPval-AA 2.1), while Claude Sonnet 5.5 is better at 1 benchmark (Terminal-Bench 4.0).

Claude Opus 5.5 significantly outperforms across most benchmarks.

Mon Sep 28 2026 • llm-stats.com

Human preference

Blind head-to-head votes and playground preference scores

Pricing Analysis

Price comparison per million tokens

Claude Sonnet 5.5 costs less

For input processing, Claude Opus 5.5 ($4.00/1M tokens) is 2.0x more expensive than Claude Sonnet 5.5 ($2.00/1M tokens).

For output processing, Claude Opus 5.5 ($20.00/1M tokens) is 2.0x more expensive than Claude Sonnet 5.5 ($10.00/1M tokens).

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

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

Lowest available price from all providers
Mon Sep 28 2026 • llm-stats.com
Anthropic
Claude Opus 5.5
Input tokens$4.00
Output tokens$20.00
Best providerAnthropic
Anthropic
Claude Sonnet 5.5
Input tokens$2.00
Output tokens$10.00
Best providerAnthropic
Notice missing or incorrect data?Start an Issue→

Context Window

Maximum input and output token capacity

Both models have the same input context window of 1,000,000 tokens. Both models can generate responses up to 128,000 tokens.

Anthropic
Claude Opus 5.5
Input1,000,000 tokens
Output128,000 tokens
Anthropic
Claude Sonnet 5.5
Input1,000,000 tokens
Output128,000 tokens
Mon Sep 28 2026 • llm-stats.com

Input capabilities

Documented input modalities across available providers

Both Claude Opus 5.5 and Claude Sonnet 5.5 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 5.5

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 5.5

Proprietary

Closed source

Release Timeline

When each model was launched

Claude Opus 5.5 was released on 2026-09-22, while Claude Sonnet 5.5 was released on 2026-09-28.

Claude Sonnet 5.5 is 0 month newer than Claude Opus 5.5.

Claude Opus 5.5

Sep 22, 2026

6 days ago

Claude Sonnet 5.5

Sep 28, 2026

0 days ago

6d newer

Knowledge Cutoff

When training data ends

Both models have the same knowledge cutoff date of 2026-06-01.

They should have similar awareness of historical events and information up to this date.

Claude Opus 5.5

Jun 2026

Claude Sonnet 5.5

Jun 2026

Provider Availability

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

Claude Opus 5.5

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

Claude Sonnet 5.5

anthropic logo
Anthropic
Input Price:Input: $2.00/1MOutput Price:Output: $10.00/1M
* 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 5.5 side-by-side, then vote on the output you prefer.

Claude Opus 5.5
✓ Preferred
Claude Sonnet 5.5
Open in Playground

FAQ

Common questions about Claude Opus 5.5 vs Claude Sonnet 5.5.

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

Claude Opus 5.5 and Claude Sonnet 5.5 are closely matched on the LLM Stats Score at 60.0 and 51.5. Claude Opus 5.5 is made by Anthropic and Claude Sonnet 5.5 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 5.5 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 5.5 scores OSWorld 2.1 (partial): 80.1%, Terminal-Bench 4.0: 70.6%, Humanity's Last Exam (with tools): 64.5%, Chartography (no tools): 61.6%, GDPval-AA 2.1: 61.5%.

Is Claude Opus 5.5 cheaper than Claude Sonnet 5.5?

Claude Sonnet 5.5 is 2.0x cheaper for input tokens. Claude Opus 5.5 costs $4.00/M input and $20.00/M output via anthropic. Claude Sonnet 5.5 costs $2.00/M input and $10.00/M output via anthropic.

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

Claude Opus 5.5 supports 1.0M tokens and Claude Sonnet 5.5 supports 1.0M 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 5.5?

Key differences include LLM Stats Score (60.0 vs 51.5), input pricing ($4.00 vs $2.00/M). See the full comparison above for benchmark-by-benchmark results.

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