GPT-5 vs Grok 4 Fast
GPT-5 and Grok 4 Fast are closely matched at 34.2 and 32.0 on the LLM Stats Score. Grok 4 Fast is 12.5x cheaper per token.
OpenAI · xAI · Updated for 2026
Which is better?
GPT-5 and Grok 4 Fast are closely matched on the overall LLM Stats Score at 34.2 and 32.0.
In the 5 individual benchmarks reported for both models, GPT-5 wins 3; this is a narrower head-to-head signal than the composite indexes.
On price, Grok 4 Fast is roughly 12.5x 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.
Based on current LLM Stats indexes, shared benchmarks, pricing, and model metadata for 2026.
Choose GPT-5
- you value its reported benchmark strengths — it wins 3 of 5 exact shared results
Choose Grok 4 Fast
- cost matters — it's about 12.5x cheaper per token
- you process long inputs — it offers a 2,000,000 token context window
- you want the most recent training data — it shipped Aug 2025
At a glance
The differences that matter most.
Capability indexes
Additional strengths measured across groups of related public benchmarks
Individual benchmarks
34 reported for GPT-5 · 7 for Grok 4 Fast
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.
Human preference
Blind head-to-head votes and playground preference scores
Pricing Analysis
Price comparison per million tokens
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
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.
Input capabilities
Documented input modalities across available providers
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
Grok 4 Fast
License
Usage and distribution terms
Both models are licensed under proprietary licenses.
Both models have usage restrictions defined by their respective organizations.
Proprietary
Closed source
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.
Aug 7, 2025
1.1 years ago
Aug 28, 2025
1.0 years ago
3w newerKnowledge 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.
Sep 2024
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Provider Availability
GPT-5 is available from OpenAI. Grok 4 Fast is available from xAI.
GPT-5
Grok 4 Fast
Outputs Comparison
Judge for yourself.
Run your own prompts against GPT-5 and Grok 4 Fast side-by-side, then vote on the output you prefer.
FAQ
Common questions about GPT-5 vs Grok 4 Fast.