Model Comparison
Gemini 2.5 Pro vs Grok 4 FastWhich is better in 2026?
Grok 4 Fast significantly outperforms across most benchmarks. Grok 4 Fast is 12.5x cheaper per token.
Verdict: Gemini 2.5 Pro vs Grok 4 Fast — which is better?
Gemini 2.5 Pro (by Google) 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.
Gemini 2.5 Pro outperforms in 0 benchmarks, while Grok 4 Fast is better at 4 benchmarks (AIME 2025, GPQA, Humanity's Last Exam, SimpleQA). Grok 4 Fast significantly outperforms across most benchmarks.
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.
Choose Gemini 2.5 Pro if…
- you want predictable pricing at $1.25/M input and $10.00/M output
Choose Grok 4 Fast if…
- you want the strongest raw capability — it leads on 4 of 4 shared benchmarks
- 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
Performance Benchmarks
Comparative analysis across standard metrics
Gemini 2.5 Pro outperforms in 0 benchmarks, while Grok 4 Fast is better at 4 benchmarks (AIME 2025, GPQA, Humanity's Last Exam, SimpleQA).
Grok 4 Fast significantly outperforms across most benchmarks.
Arena Performance
Human preference votes
Pricing Analysis
Price comparison per million tokens
For input processing, Gemini 2.5 Pro ($1.25/1M tokens) is 6.3x more expensive than Grok 4 Fast ($0.20/1M tokens).
For output processing, Gemini 2.5 Pro ($10.00/1M tokens) is 20.0x more expensive than Grok 4 Fast ($0.50/1M tokens).
In conclusion, Gemini 2.5 Pro 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 Gemini 2.5 Pro's 1,048,576 tokens. Gemini 2.5 Pro can generate longer responses up to 65,536 tokens, while Grok 4 Fast is limited to 30,000 tokens.
Input Capabilities
Supported data types and modalities
Both Gemini 2.5 Pro and Grok 4 Fast support multimodal inputs.
They are both capable of processing various types of data, offering versatility in application.
Gemini 2.5 Pro
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
Gemini 2.5 Pro was released on 2025-05-20, while Grok 4 Fast was released on 2025-08-28.
Grok 4 Fast is 3 months newer than Gemini 2.5 Pro.
May 20, 2025
1.2 years ago
Aug 28, 2025
10 months ago
3mo newerKnowledge Cutoff
When training data ends
Gemini 2.5 Pro has a documented knowledge cutoff of 2025-01-31, while Grok 4 Fast's cutoff date is not specified.
We can confirm Gemini 2.5 Pro's training data extends to 2025-01-31, but cannot make a direct comparison without Grok 4 Fast's cutoff date.
Jan 2025
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Provider Availability
Gemini 2.5 Pro is available from Google. Grok 4 Fast is available from xAI.
Gemini 2.5 Pro
Grok 4 Fast
Outputs Comparison
Key Takeaways
No standout differentiators in the data we have for this pair.
Gemini 2.5 ProGrok 4 FastDetailed Comparison
Interactive Arena
Judge for yourself.
Run your own prompts against Gemini 2.5 Pro and Grok 4 Fast side-by-side, then vote on the output you prefer.
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FAQ
Common questions about Gemini 2.5 Pro vs Grok 4 Fast.