Grok 4 Fast vs Kimi K3.1 Pro
Kimi K3.1 Pro leads the LLM Stats Score 55.5 to 30.9. Grok 4 Fast is 14.5x cheaper per token.
xAI · Moonshot AI · Updated for 2026
Which is better?
Kimi K3.1 Pro leads the overall LLM Stats Score 55.5 to 30.9, ranking #5 overall.
In the 3 individual benchmarks reported for both models, Kimi K3.1 Pro wins 3; this is a narrower head-to-head signal than the composite indexes.
On price, Grok 4 Fast is roughly 14.5x 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 Grok 4 Fast
- cost matters — it's about 14.5x cheaper per token
- you process long inputs — it offers a 2,000,000 token context window
Choose Kimi K3.1 Pro
- overall performance matters — it scores 55.5 and ranks #5 on LLM Stats
- your work emphasizes reasoning and coding — it leads those capability indexes
- you value its reported benchmark strengths — it wins 3 of 3 exact shared results
- you want the most recent training data — it shipped Oct 2026
At a glance
The differences that matter most.
Capability indexes
Additional strengths measured across groups of related public benchmarks
Individual benchmarks
7 reported for Grok 4 Fast · 30 for Kimi K3.1 Pro
Grok 4 Fast outperforms in 0 benchmarks, while Kimi K3.1 Pro is better at 3 benchmarks (BrowseComp, GPQA, Humanity's Last Exam).
Kimi K3.1 Pro significantly outperforms across most benchmarks.
Human preference
Blind head-to-head votes and playground preference scores
Pricing Analysis
Price comparison per million tokens
For input processing, Grok 4 Fast ($0.20/1M tokens) is 10.0x cheaper than Kimi K3.1 Pro ($2.00/1M tokens).
For output processing, Grok 4 Fast ($0.50/1M tokens) is 20.0x cheaper than Kimi K3.1 Pro ($10.00/1M tokens).
In conclusion, Kimi K3.1 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 Kimi K3.1 Pro's 1,048,576 tokens. Kimi K3.1 Pro can generate longer responses up to 1,048,576 tokens, while Grok 4 Fast is limited to 30,000 tokens.
Input capabilities
Documented input modalities across available providers
Both Grok 4 Fast and Kimi K3.1 Pro support multimodal inputs.
They are both capable of processing various types of data, offering versatility in application.
Grok 4 Fast
Kimi K3.1 Pro
Release Timeline
When each model was launched
Grok 4 Fast was released on 2025-08-28, while Kimi K3.1 Pro was released on 2026-10-23.
Kimi K3.1 Pro is 14 months newer than Grok 4 Fast.
Aug 28, 2025
1.2 years ago
Oct 23, 2026
4 days ago
1.2yr newerKnowledge Cutoff
When training data ends
Neither model specifies a knowledge cutoff date.
Unable to compare the recency of their training data.
Provider Availability
Grok 4 Fast is available from xAI. Kimi K3.1 Pro is available from Moonshot AI.
Grok 4 Fast
Kimi K3.1 Pro
Outputs Comparison
Judge for yourself.
Run your own prompts against Grok 4 Fast and Kimi K3.1 Pro side-by-side, then vote on the output you prefer.
FAQ
Common questions about Grok 4 Fast vs Kimi K3.1 Pro.