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Claude Opus 5.5 vs o3

Claude Opus 5.5 leads the LLM Stats Score 59.7 to 31.1. o3 is 2.3x cheaper per token.

Anthropic · OpenAI · Updated for 2026

Which is better?

Claude Opus 5.5 leads the overall LLM Stats Score 59.7 to 31.1, ranking #1 overall.

On price, o3 is roughly 2.3x 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 o3

  • cost matters — it's about 2.3x cheaper per token

At a glance

The differences that matter most.

Claude Opus 5.5
Anthropic
o3
OpenAI
Core performance indexes
LLM Stats Score
59.7
#1
31.1
#119
Reasoning
57.8
#1
30.7
#121
Coding
51.7
#1
14.9
#136
Agents
44.5
#2
4.0
#165
Cost, coverage & limits
Benchmark wins
—
—
Input price
$4.00 / M
$2.00 / M
Output price
$20.00 / M
$8.00 / 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
o3
Math
42.5#5
25.5#108
Vision
42.8#1
21.6#64
Tool use
32.9#2
10.8#122
Multimodal
42.5#1
25.6#47
Conservative TrueSkill rating · higher is betterHow scores work

Individual benchmarks

31 reported for Claude Opus 5.5 · 22 for o3

No common benchmarks found

Claude Opus 5.5 and o3don'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

o3 costs less

For input processing, Claude Opus 5.5 ($4.00/1M tokens) is 2.0x more expensive than o3 ($2.00/1M tokens).

For output processing, Claude Opus 5.5 ($20.00/1M tokens) is 2.5x more expensive than o3 ($8.00/1M tokens).

In conclusion, Claude Opus 5.5 is more expensive than o3.*

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

Lowest available price from all providers
Wed Sep 23 2026 • llm-stats.com
Anthropic
Claude Opus 5.5
Input tokens$4.00
Output tokens$20.00
Best providerAnthropic
OpenAI
o3
Input tokens$2.00
Output tokens$8.00
Best providerOpenAI
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 o3's 200,000 tokens. Claude Opus 5.5 can generate longer responses up to 128,000 tokens, while o3 is limited to 100,000 tokens.

Anthropic
Claude Opus 5.5
Input1,000,000 tokens
Output128,000 tokens
OpenAI
o3
Input200,000 tokens
Output100,000 tokens
Wed Sep 23 2026 • llm-stats.com

Input capabilities

Documented input modalities across available providers

Both Claude Opus 5.5 and o3 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

o3

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

o3

Proprietary

Closed source

Release Timeline

When each model was launched

Claude Opus 5.5 was released on 2026-09-22, while o3 was released on 2025-04-16.

Claude Opus 5.5 is 17 months newer than o3.

Claude Opus 5.5

Sep 22, 2026

0 days ago

1.4yr newer
o3

Apr 16, 2025

1.4 years ago

Knowledge Cutoff

When training data ends

Claude Opus 5.5 has a knowledge cutoff of 2026-06-01, while o3 has a cutoff of 2024-05-31.

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 o3 (2024-05-31).

Claude Opus 5.5

Jun 2026

2.1 yr newer
o3

May 2024

Provider Availability

Claude Opus 5.5 is available from Anthropic. o3 is available from OpenAI.

Claude Opus 5.5

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

o3

openai logo
OpenAI
Input Price:Input: $2.00/1MOutput Price:Output: $8.00/1M
* 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 o3 side-by-side, then vote on the output you prefer.

Claude Opus 5.5
✓ Preferred
o3
Open in Playground

FAQ

Common questions about Claude Opus 5.5 vs o3.

Which is better, Claude Opus 5.5 or o3?

Claude Opus 5.5 leads the LLM Stats Score 59.7 to 31.1. Claude Opus 5.5 is made by Anthropic and o3 is made by OpenAI. 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 o3 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%. o3 scores COLLIE: 98.4%, AIME 2024: 91.6%, ARC-AGI: 88.0%, MathVista: 86.8%, AIME 2025: 86.4%.

Is Claude Opus 5.5 cheaper than o3?

o3 is 2.0x cheaper for input tokens. Claude Opus 5.5 costs $4.00/M input and $20.00/M output via anthropic. o3 costs $2.00/M input and $8.00/M output via openai.

What are the context window sizes for Claude Opus 5.5 and o3?

Claude Opus 5.5 supports 1.0M tokens and o3 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 o3?

Key differences include LLM Stats Score (59.7 vs 31.1), context window (1.0M vs 200K), input pricing ($4.00 vs $2.00/M). See the full comparison above for benchmark-by-benchmark results.

Who makes Claude Opus 5.5 and o3?

Claude Opus 5.5 is developed by Anthropic and o3 is developed by OpenAI.

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