Grok 4.1 Fast vs Gemini 2.5 Flash
xAI's Grok 4.1 Fast against Google's Gemini 2.5 Flash — pricing, benchmarks, context, and best use cases compared side by side.
Grok 4.1 Fast leads on quality (Elo 1355 vs 1315) and is also 7% cheaper — a clear value winner. Grok 4.1 Fast offers a larger context window (2M vs 1M).
| Input Price | $0.20/1M | $0.15/1M |
| Output Price | $0.50/1M | $0.60/1M |
| Blended Price | $0.35/1M | $0.38/1M |
| LMSYS Elo | 1355 | 1315 |
| Context Window | 2,000,000 | 1,000,000 |
| Provider | xAI |
Pricing breakdown
When comparing LLM API pricing, Gemini 2.5 Flash charges $0.15 per 1M input tokens compared to Grok 4.1 Fast's $0.20 — a 25% difference. For output tokens, Grok 4.1 Fast costs $0.50/1M versus $0.60/1M for Gemini 2.5 Flash. On a blended basis (averaging input and output), Grok 4.1 Fast comes in at $0.35/1M tokens versus $0.38/1M for Gemini 2.5 Flash.
Quality & benchmarks
On the LMSYS Chatbot Arena leaderboard — a crowd-sourced benchmark based on blind human preference voting — Grok 4.1 Fast scores 1355 Elo compared to Gemini 2.5 Flash's 1315, a 40-point advantage. While Grok 4.1 Fast has the edge, both models are competitive. Grok 4.1 Fast excels at massive context processing, budget real-time apps, and high-throughput tasks, while Gemini 2.5 Flash is well-suited for bulk document processing, large-scale summarization, budget-sensitive apps.
Context window comparison
Grok 4.1 Fast provides a significantly larger context window at 2M tokens compared to Gemini 2.5 Flash's 1M tokens — 2.0x more capacity for processing long documents, large codebases, or extended conversations. With 2M tokens, Grok 4.1 Fast can handle entire books, repositories, or multi-document analysis in a single prompt.
Monthly cost estimate
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