Model Comparison

GPT-5.1 Thinking vs Grok 4.5Which is better in 2026?

Grok 4.5 significantly outperforms across most benchmarks. Grok 4.5 is 1.1x cheaper per token.

Verdict: GPT-5.1 Thinking vs Grok 4.5 — which is better?

GPT-5.1 Thinking (by OpenAI) and Grok 4.5 (by xAI) are two of the AI models people compare most. Here is how they stack up on benchmarks, price and capabilities, and which one to pick in 2026.

GPT-5.1 Thinking outperforms in 0 benchmarks, while Grok 4.5 is better at 1 benchmark (GPQA). Grok 4.5 significantly outperforms across most benchmarks.

On price, Grok 4.5 is roughly 1.1x cheaper per token on a blended 3:1 input/output basis, which adds up quickly at production volume.

Grok 4.5 also accepts a larger context window (500,000 input tokens), making it the stronger choice for long documents and large codebases.

Choose GPT-5.1 Thinking if…

  • you want predictable pricing at $1.25/M input and $10.00/M output

Choose Grok 4.5 if…

  • you want the strongest raw capability — it leads on 1 of 1 shared benchmarks
  • cost matters — it's about 1.1x cheaper per token
  • you process long inputs — it offers a 500,000 token context window
  • you want the most recent training data — it shipped Jul 2026

Performance Benchmarks

Comparative analysis across standard metrics

1 benchmarks

GPT-5.1 Thinking outperforms in 0 benchmarks, while Grok 4.5 is better at 1 benchmark (GPQA).

Grok 4.5 significantly outperforms across most benchmarks.

Thu Jul 23 2026 • llm-stats.com

Arena Performance

Human preference votes

Pricing Analysis

Price comparison per million tokens

Grok 4.5 costs less

For input processing, GPT-5.1 Thinking ($1.25/1M tokens) is 1.6x cheaper than Grok 4.5 ($2.00/1M tokens).

For output processing, GPT-5.1 Thinking ($10.00/1M tokens) is 1.7x more expensive than Grok 4.5 ($6.00/1M tokens).

In conclusion, GPT-5.1 Thinking is more expensive than Grok 4.5.*

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

Lowest available price from all providers
Thu Jul 23 2026 • llm-stats.com
OpenAI
GPT-5.1 Thinking
Input tokens$1.25
Output tokens$10.00
Best providerOpenAI
xAI
Grok 4.5
Input tokens$2.00
Output tokens$6.00
Best providerxAI
Notice missing or incorrect data?Start an Issue→

Context Window

Maximum input and output token capacity

Grok 4.5 accepts 500,000 input tokens compared to GPT-5.1 Thinking's 400,000 tokens. Only GPT-5.1 Thinking specifies output context (128,000 tokens).

OpenAI
GPT-5.1 Thinking
Input400,000 tokens
Output128,000 tokens
xAI
Grok 4.5
Input500,000 tokens
Output- tokens
Thu Jul 23 2026 • llm-stats.com

Input Capabilities

Supported data types and modalities

Both GPT-5.1 Thinking and Grok 4.5 support multimodal inputs.

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

GPT-5.1 Thinking

Text
Images
Audio
Video

Grok 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.

GPT-5.1 Thinking

Proprietary

Closed source

Grok 4.5

Proprietary

Closed source

Release Timeline

When each model was launched

GPT-5.1 Thinking was released on 2025-11-12, while Grok 4.5 was released on 2026-07-16.

Grok 4.5 is 8 months newer than GPT-5.1 Thinking.

GPT-5.1 Thinking

Nov 12, 2025

8 months ago

Grok 4.5

Jul 16, 2026

1 weeks ago

8mo newer

Knowledge Cutoff

When training data ends

Grok 4.5 has a documented knowledge cutoff of 2026-02-01, while GPT-5.1 Thinking's cutoff date is not specified.

We can confirm Grok 4.5's training data extends to 2026-02-01, but cannot make a direct comparison without GPT-5.1 Thinking's cutoff date.

GPT-5.1 Thinking

—

Grok 4.5

Feb 2026

Provider Availability

GPT-5.1 Thinking is available from OpenAI. Grok 4.5 is available from xAI.

GPT-5.1 Thinking

openai logo
OpenAI
Input Price:Input: $1.25/1MOutput Price:Output: $10.00/1M

Grok 4.5

xai logo
xAI
Input Price:Input: $2.00/1MOutput Price:Output: $6.00/1M
* Prices shown are per million tokens

Outputs Comparison

Notice missing or incorrect data?Start an Issue discussion→

Key Takeaways

OpenAI
Less expensive input tokens
xAI
Larger context window (500,000 tokens)
Less expensive output tokens
Higher GPQA score (93.0% vs 88.1%)

Detailed Comparison

Interactive Arena

Judge for yourself.

Run your own prompts against GPT-5.1 Thinking and Grok 4.5 side-by-side, then vote on the output you prefer.

GPT-5.1 Thinking
✓ Preferred
Grok 4.5
Open in Playground
AI Model Comparison Table
Feature
OpenAI
GPT-5.1 Thinking
xAI
Grok 4.5

FAQ

Common questions about GPT-5.1 Thinking vs Grok 4.5.

Which is better, GPT-5.1 Thinking or Grok 4.5?

Grok 4.5 significantly outperforms across most benchmarks. GPT-5.1 Thinking is made by OpenAI and Grok 4.5 is made by xAI. The best choice depends on your use case — compare their benchmark scores, pricing, and capabilities above.

How does GPT-5.1 Thinking compare to Grok 4.5 in benchmarks?

GPT-5.1 Thinking scores Tau2 Telecom: 95.6%, AIME 2025: 94.0%, BrowseComp Long Context 128k: 90.0%, GPQA: 88.1%, MMMU: 85.4%. Grok 4.5 scores GPQA: 93.0%, Terminal-Bench 2.1: 83.3%, Artificial Analysis Coding Agent Index v1.1: 76.0%, SWE-Bench Pro: 64.7%, AA-Omniscience Index: 63.0%.

Is GPT-5.1 Thinking cheaper than Grok 4.5?

GPT-5.1 Thinking is 1.6x cheaper for input tokens. GPT-5.1 Thinking costs $1.25/M input and $10.00/M output via openai. Grok 4.5 costs $2.00/M input and $6.00/M output via xai.

What are the context window sizes for GPT-5.1 Thinking and Grok 4.5?

GPT-5.1 Thinking supports 400K tokens and Grok 4.5 supports 500K tokens. A larger context window lets you process longer documents, conversations, or codebases in a single request.

What are the main differences between GPT-5.1 Thinking and Grok 4.5?

Key differences include context window (400K vs 500K), input pricing ($1.25 vs $2.00/M). See the full comparison above for benchmark-by-benchmark results.

Who makes GPT-5.1 Thinking and Grok 4.5?

GPT-5.1 Thinking is developed by OpenAI and Grok 4.5 is developed by xAI.

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