Model Comparison

GPT-5.4 vs Grok 4 FastWhich is better in 2026?

GPT-5.4 significantly outperforms across most benchmarks. Grok 4 Fast is 20.5x cheaper per token.

Verdict: GPT-5.4 vs Grok 4 Fast — which is better?

GPT-5.4 (by OpenAI) and Grok 4 Fast (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-5.4 outperforms in 3 benchmarks (BrowseComp, GPQA, Humanity's Last Exam), while Grok 4 Fast is better at 0 benchmarks. GPT-5.4 significantly outperforms across most benchmarks.

On price, Grok 4 Fast is roughly 20.5x cheaper per token on a blended 3:1 input/output basis, which adds up quickly at production volume.

Grok 4 Fast also accepts a larger context window (2,000,000 input tokens), making it the stronger choice for long documents and large codebases.

Choose GPT-5.4 if…

  • you want the strongest raw capability — it leads on 3 of 3 shared benchmarks
  • you want the most recent training data — it shipped Mar 2026

Choose Grok 4 Fast if…

  • cost matters — it's about 20.5x cheaper per token
  • you process long inputs — it offers a 2,000,000 token context window
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Performance Benchmarks

Comparative analysis across standard metrics

3 benchmarks

GPT-5.4 outperforms in 3 benchmarks (BrowseComp, GPQA, Humanity's Last Exam), while Grok 4 Fast is better at 0 benchmarks.

GPT-5.4 significantly outperforms across most benchmarks.

Sun Jun 07 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-5.4 ($2.50/1M tokens) is 12.5x more expensive than Grok 4 Fast ($0.20/1M tokens).

For output processing, GPT-5.4 ($15.00/1M tokens) is 30.0x more expensive than Grok 4 Fast ($0.50/1M tokens).

In conclusion, GPT-5.4 is more expensive than Grok 4 Fast.*

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

Lowest available price from all providers
Sun Jun 07 2026 • llm-stats.com
OpenAI
GPT-5.4
Input tokens$2.50
Output tokens$15.00
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-5.4's 1,000,000 tokens. GPT-5.4 can generate longer responses up to 128,000 tokens, while Grok 4 Fast is limited to 30,000 tokens.

OpenAI
GPT-5.4
Input1,000,000 tokens
Output128,000 tokens
xAI
Grok 4 Fast
Input2,000,000 tokens
Output30,000 tokens
Sun Jun 07 2026 • llm-stats.com

Input Capabilities

Supported data types and modalities

Both GPT-5.4 and Grok 4 Fast support multimodal inputs.

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

GPT-5.4

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-5.4

Proprietary

Closed source

Grok 4 Fast

Proprietary

Closed source

Release Timeline

When each model was launched

GPT-5.4 was released on 2026-03-05, while Grok 4 Fast was released on 2025-08-28.

GPT-5.4 is 6 months newer than Grok 4 Fast.

GPT-5.4

Mar 5, 2026

3 months ago

6mo newer
Grok 4 Fast

Aug 28, 2025

9 months ago

Knowledge Cutoff

When training data ends

Neither model specifies a knowledge cutoff date.

Unable to compare the recency of their training data.

No cutoff dates available

Provider Availability

GPT-5.4 is available from OpenAI. Grok 4 Fast is available from xAI.

GPT-5.4

openai logo
OpenAI
Input Price:Input: $2.50/1MOutput Price:Output: $15.00/1M

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

Notice missing or incorrect data?Start an Issue discussion→

Key Takeaways

OpenAI
Higher BrowseComp score (82.7% vs 44.9%)
Higher GPQA score (92.8% vs 85.7%)
Higher Humanity's Last Exam score (39.8% 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-5.4
xAI
Grok 4 Fast

FAQ

Common questions about GPT-5.4 vs Grok 4 Fast.

Which is better, GPT-5.4 or Grok 4 Fast?

GPT-5.4 significantly outperforms across most benchmarks. GPT-5.4 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-5.4 compare to Grok 4 Fast in benchmarks?

GPT-5.4 scores Tau2 Telecom: 98.9%, ARC-AGI: 93.7%, Graphwalks BFS <128k: 93.0%, GPQA: 92.8%, Graphwalks parents <128k: 89.8%. Grok 4 Fast scores SimpleQA: 95.0%, HMMT 2025: 93.3%, AIME 2025: 92.0%, GPQA: 85.7%, LiveCodeBench: 80.0%.

Is GPT-5.4 cheaper than Grok 4 Fast?

Grok 4 Fast is 12.5x cheaper for input tokens. GPT-5.4 costs $2.50/M input and $15.00/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-5.4 and Grok 4 Fast?

GPT-5.4 supports 1.0M 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-5.4 and Grok 4 Fast?

Key differences include context window (1.0M vs 2.0M), input pricing ($2.50 vs $0.20/M). See the full comparison above for benchmark-by-benchmark results.

Who makes GPT-5.4 and Grok 4 Fast?

GPT-5.4 is developed by OpenAI and Grok 4 Fast is developed by xAI.

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