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Claude Opus 5.5 vs Gemini 2.5 Flash

Claude Opus 5.5 leads the LLM Stats Score 59.7 to 21.8. Gemini 2.5 Flash is 9.4x cheaper per token.

Anthropic · Google · Updated for 2026

Which is better?

Claude Opus 5.5 leads the overall LLM Stats Score 59.7 to 21.8, ranking #1 overall.

On price, Gemini 2.5 Flash is roughly 9.4x 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

  • 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 want the most recent training data — it shipped Sep 2026

Choose Gemini 2.5 Flash

  • cost matters — it's about 9.4x cheaper per token

At a glance

The differences that matter most.

Claude Opus 5.5
Anthropic
Gemini 2.5 Flash
Google
Core performance indexes
LLM Stats Score
59.7
#1
21.8
#189
Reasoning
57.8
#1
21.4
#186
Coding
51.7
#1
8.4
#186
Cost, coverage & limits
Benchmark wins
—
—
Input price
$4.00 / M
$0.30 / M
Output price
$20.00 / M
$2.50 / M
Context window
1,000,000
1,000,000

Capability indexes

Additional strengths measured across groups of related public benchmarks

3 shared
Index
Claude Opus 5.5
Gemini 2.5 Flash
Math
42.5#5
16.2#210
Vision
42.8#1
10.9#117
Multimodal
42.5#1
19.6#76
Conservative TrueSkill rating · higher is betterHow scores work

Individual benchmarks

31 reported for Claude Opus 5.5 · 14 for Gemini 2.5 Flash

No common benchmarks found

Claude Opus 5.5 and Gemini 2.5 Flashdon'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

Gemini 2.5 Flash costs less

For input processing, Claude Opus 5.5 ($4.00/1M tokens) is 13.3x more expensive than Gemini 2.5 Flash ($0.30/1M tokens).

For output processing, Claude Opus 5.5 ($20.00/1M tokens) is 8.0x more expensive than Gemini 2.5 Flash ($2.50/1M tokens).

In conclusion, Claude Opus 5.5 is more expensive than Gemini 2.5 Flash.*

* 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
Google
Gemini 2.5 Flash
Input tokens$0.30
Output tokens$2.50
Best providerDeepinfra
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. Gemini 2.5 Flash can generate longer responses up to 1,000,000 tokens, while Claude Opus 5.5 is limited to 128,000 tokens.

Anthropic
Claude Opus 5.5
Input1,000,000 tokens
Output128,000 tokens
Google
Gemini 2.5 Flash
Input1,000,000 tokens
Output1,000,000 tokens
Tue Sep 22 2026 • llm-stats.com

Input capabilities

Documented input modalities across available providers

Both Claude Opus 5.5 and Gemini 2.5 Flash 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

Gemini 2.5 Flash

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

Gemini 2.5 Flash

Proprietary

Closed source

Release Timeline

When each model was launched

Claude Opus 5.5 was released on 2026-09-22, while Gemini 2.5 Flash was released on 2025-05-20.

Claude Opus 5.5 is 16 months newer than Gemini 2.5 Flash.

Claude Opus 5.5

Sep 22, 2026

0 days ago

1.3yr newer
Gemini 2.5 Flash

May 20, 2025

1.3 years ago

Knowledge Cutoff

When training data ends

Claude Opus 5.5 has a knowledge cutoff of 2026-06-01, while Gemini 2.5 Flash 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 Gemini 2.5 Flash (2025-01-31).

Claude Opus 5.5

Jun 2026

1.4 yr newer
Gemini 2.5 Flash

Jan 2025

Provider Availability

Claude Opus 5.5 is available from Anthropic. Gemini 2.5 Flash is available from DeepInfra, Google.

Claude Opus 5.5

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

Gemini 2.5 Flash

deepinfra logo
Deepinfra
Input Price:Input: $0.30/1MOutput Price:Output: $2.50/1M
google logo
Google
Input Price:Input: $0.30/1MOutput Price:Output: $2.50/1M
* 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 Gemini 2.5 Flash side-by-side, then vote on the output you prefer.

Claude Opus 5.5
✓ Preferred
Gemini 2.5 Flash
Open in Playground

FAQ

Common questions about Claude Opus 5.5 vs Gemini 2.5 Flash.

Which is better, Claude Opus 5.5 or Gemini 2.5 Flash?

Claude Opus 5.5 leads the LLM Stats Score 59.7 to 21.8. Claude Opus 5.5 is made by Anthropic and Gemini 2.5 Flash is made by Google. 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 Gemini 2.5 Flash 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%. Gemini 2.5 Flash scores Global-MMLU-Lite: 88.4%, AIME 2024: 88.0%, FACTS Grounding: 85.3%, GPQA: 82.8%, MMMU: 79.7%.

Is Claude Opus 5.5 cheaper than Gemini 2.5 Flash?

Gemini 2.5 Flash is 13.3x cheaper for input tokens. Claude Opus 5.5 costs $4.00/M input and $20.00/M output via anthropic. Gemini 2.5 Flash costs $0.30/M input and $2.50/M output via deepinfra.

What are the context window sizes for Claude Opus 5.5 and Gemini 2.5 Flash?

Claude Opus 5.5 supports 1.0M tokens and Gemini 2.5 Flash 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 Gemini 2.5 Flash?

Key differences include LLM Stats Score (59.7 vs 21.8), input pricing ($4.00 vs $0.30/M). See the full comparison above for benchmark-by-benchmark results.

Who makes Claude Opus 5.5 and Gemini 2.5 Flash?

Claude Opus 5.5 is developed by Anthropic and Gemini 2.5 Flash is developed by Google.

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