Model Comparison

GPT-5 vs Grok 4 Fast

GPT-5 has a slight edge in benchmark performance. Grok 4 Fast is 12.5x cheaper per token.

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Performance Benchmarks

Comparative analysis across standard metrics

5 benchmarks

GPT-5 outperforms in 3 benchmarks (AIME 2025, BrowseComp, Humanity's Last Exam), while Grok 4 Fast is better at 0 benchmarks.

GPT-5 has a slight edge in benchmark performance.

Thu May 14 2026 • llm-stats.com

Arena Performance

Human preference votes

Pricing Analysis

Price comparison per million tokens

Grok 4 Fast costs less

For input processing, GPT-5 ($1.25/1M tokens) is 6.3x more expensive than Grok 4 Fast ($0.20/1M tokens).

For output processing, GPT-5 ($10.00/1M tokens) is 20.0x more expensive than Grok 4 Fast ($0.50/1M tokens).

In conclusion, GPT-5 is more expensive than Grok 4 Fast.*

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

Lowest available price from all providers
Thu May 14 2026 • llm-stats.com
OpenAI
GPT-5
Input tokens$1.25
Output tokens$10.00
Best providerOpenAI
xAI
Grok 4 Fast
Input tokens$0.20
Output tokens$0.50
Best providerxAI
Notice missing or incorrect data?Start an Issue→

Context Window

Maximum input and output token capacity

Grok 4 Fast accepts 2,000,000 input tokens compared to GPT-5's 400,000 tokens. GPT-5 can generate longer responses up to 128,000 tokens, while Grok 4 Fast is limited to 30,000 tokens.

OpenAI
GPT-5
Input400,000 tokens
Output128,000 tokens
xAI
Grok 4 Fast
Input2,000,000 tokens
Output30,000 tokens
Thu May 14 2026 • llm-stats.com

Input Capabilities

Supported data types and modalities

Both GPT-5 and Grok 4 Fast support multimodal inputs.

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

GPT-5

Text
Images
Audio
Video

Grok 4 Fast

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

Proprietary

Closed source

Grok 4 Fast

Proprietary

Closed source

Release Timeline

When each model was launched

GPT-5 was released on 2025-08-07, while Grok 4 Fast was released on 2025-08-28.

Grok 4 Fast is 1 month newer than GPT-5.

GPT-5

Aug 7, 2025

9 months ago

Grok 4 Fast

Aug 28, 2025

8 months ago

3w newer

Knowledge Cutoff

When training data ends

GPT-5 has a documented knowledge cutoff of 2024-09-30, while Grok 4 Fast's cutoff date is not specified.

We can confirm GPT-5's training data extends to 2024-09-30, but cannot make a direct comparison without Grok 4 Fast's cutoff date.

GPT-5

Sep 2024

Grok 4 Fast

—

Provider Availability

GPT-5 is available from OpenAI. Grok 4 Fast is available from xAI.

GPT-5

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

Grok 4 Fast

xai logo
xAI
Input Price:Input: $0.20/1MOutput Price:Output: $0.50/1M
* Prices shown are per million tokens

Outputs Comparison

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Key Takeaways

OpenAI
Higher AIME 2025 score (94.6% vs 92.0%)
Higher BrowseComp score (54.9% vs 44.9%)
Higher Humanity's Last Exam score (24.8% vs 20.0%)
xAI
Larger context window (2,000,000 tokens)
Less expensive input tokens
Less expensive output tokens

Detailed Comparison

AI Model Comparison Table
Feature
OpenAI
GPT-5
xAI
Grok 4 Fast

FAQ

Common questions about GPT-5 vs Grok 4 Fast.

Which is better, GPT-5 or Grok 4 Fast?

GPT-5 has a slight edge in benchmark performance. GPT-5 is made by OpenAI and Grok 4 Fast is made by xAI. The best choice depends on your use case — compare their benchmark scores, pricing, and capabilities above.

How does GPT-5 compare to Grok 4 Fast in benchmarks?

GPT-5 scores SWE-Lancer (IC-Diamond subset): 100.0%, COLLIE: 99.0%, Tau2 Telecom: 96.7%, OpenAI-MRCR: 2 needle 128k: 95.2%, AIME 2025: 94.6%. Grok 4 Fast scores SimpleQA: 95.0%, HMMT 2025: 93.3%, AIME 2025: 92.0%, GPQA: 85.7%, LiveCodeBench: 80.0%.

Is GPT-5 cheaper than Grok 4 Fast?

Grok 4 Fast is 6.3x cheaper for input tokens. GPT-5 costs $1.25/M input and $10.00/M output via openai. Grok 4 Fast costs $0.20/M input and $0.50/M output via xai.

What are the context window sizes for GPT-5 and Grok 4 Fast?

GPT-5 supports 400K tokens and Grok 4 Fast supports 2.0M 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 and Grok 4 Fast?

Key differences include context window (400K vs 2.0M), input pricing ($1.25 vs $0.20/M). See the full comparison above for benchmark-by-benchmark results.

Who makes GPT-5 and Grok 4 Fast?

GPT-5 is developed by OpenAI and Grok 4 Fast is developed by xAI.