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Comparison · 2 models · Updated Oct 4, 2026

GPT-5.1 Chat vs Grok 4.1 Fast

Grok 4.1 Fast comes out ahead, 71 to 38 on our weighted score, and it is the cheaper option too.

  1. OpenAI

    GPT-5.1 Chat

    Released Nov 13, 2025

    38/100
    • ECI—
    • Price$1.25 / $10.00
    • Context128K
    Full specs Remove GPT-5.1 Chat
  2. Our pick

    xAI

    Grok 4.1 Fast

    Released Nov 19, 2025

    71/100
    • ECI—
    • Price$0.20 / $0.50
    • Context2M
    Full specs Remove Grok 4.1 Fast

  3. Add a model

    Make it a three-way comparison.

01 — Verdict

Grok 4.1 Fast is our pick

Grok 4.1 Fast is the better all-round choice, scoring 71/100 against GPT-5.1 Chat (38). It leads on price and context window. GPT-5.1 Chat wins on inputs & features. The score weighs price 50%, inputs & features 30%, context window 20%. None of the shared benchmarks cover every model here yet, so capability is left out of this verdict.

  • CapabilityNot enough dataNo independent benchmark covers every model here yet
  • Lowest priceGrok 4.1 FastGrok 4.1 Fast $0.275 · GPT-5.1 Chat $3.44 per 1M tokens (3:1 blend)
  • Longest contextGrok 4.1 FastGrok 4.1 Fast 2,000,000 · GPT-5.1 Chat 128,000 tokens
  • Widest inputsSame inputsGPT-5.1 Chat: Text, Images · Grok 4.1 Fast: Text, Images
  • Self-hostingNo open weightsBoth are available only through APIs
How the score is built
MeasureWeightGPT-5.1 ChatGrok 4.1 Fast
Price50%2476
Inputs & features30%7060
Context window20%2472
Overall100%38/10071/100

Left out because at least one model lacks the data: capability. The remaining weights were rescaled.

02 — Side by side

Every spec in one table

Highlighted cells lead their row. Dashes mean the data is not published.

GPT-5.1 Chat vs Grok 4.1 Fast specifications side by side
SpecificationGPT-5.1 ChatOpenAIGrok 4.1 FastxAI
Capability
Capabilities Index (ECI)——
ECI rank——
Price per million tokens
Input$1.25$0.20 (best)
Output$10.00$0.50 (best)
Cached input——
Blended (3:1)$3.44$0.275 (best)
Long-context rateSame rateSame rate
Price sourceMedian of 2 providersMedian of 2 providers
Limits
Context window128,000 tokens2,000,000 tokens (best)
Max output16,384 tokens30,000 tokens (best)
Inputs and features
TextYesYes
ImagesYesYes
PDFsNoNo
AudioNoNo
VideoNoNo
ReasoningYesNo
Tool callingYesYes
Structured outputYesYes
Availability
WeightsProprietaryProprietary
API model ID——
API providers22
ReleasedNov 13, 2025Nov 19, 2025
Knowledge cutoffSep 30, 2024—
03 — Cost

What would a month cost?

Enter your expected volume in millions of tokens. List prices only; caching and batch discounts would lower these.

  • GPT-5.1 Chat$32.50
  • Grok 4.1 Fast$3.00
04 — Questions

Which should you choose?

Which is better: GPT-5.1 Chat or Grok 4.1 Fast?

Grok 4.1 Fast is the better all-round choice, scoring 71/100 against GPT-5.1 Chat (38). It leads on price and context window. GPT-5.1 Chat wins on inputs & features. The score weighs price 50%, inputs & features 30%, context window 20%. None of the shared benchmarks cover every model here yet, so capability is left out of this verdict.

Which is cheaper, GPT-5.1 Chat or Grok 4.1 Fast?

Grok 4.1 Fast is cheaper at $0.20 input / $0.50 output per million tokens (median across 2 API providers). GPT-5.1 Chat costs $1.25 input / $10.00 output per million tokens (median across 2 API providers). At a typical mix of three input tokens to one output token, that is $0.275 per million tokens for Grok 4.1 Fast versus $3.44 for GPT-5.1 Chat (12× as much).

Which scores higher on benchmarks?

There is no independent benchmark that covers both models yet. GPT-5.1 Chat has not been scored yet and Grok 4.1 Fast has not been scored yet.

Which is better for coding?

There are no published SWE-bench Verified results for GPT-5.1 Chat and Grok 4.1 Fast yet, so there is no like-for-like coding score. Test both on a sample of your own tasks. Both support tool calling for agent workflows.

Which has the bigger context window?

Grok 4.1 Fast has the largest context window at 2,000,000 tokens, against 128,000 for GPT-5.1 Chat. Maximum output per response: GPT-5.1 Chat up to 16,384, Grok 4.1 Fast up to 30,000 tokens.

Which can read images, PDFs, audio or video?

GPT-5.1 Chat accepts text and images; Grok 4.1 Fast accepts text and images. They handle the same number of input types.

Are any of these open source?

No. GPT-5.1 Chat and Grok 4.1 Fast are proprietary and only available through APIs and apps.

Which is newer?

Grok 4.1 Fast is the newest, released Nov 19, 2025. GPT-5.1 Chat came out Nov 13, 2025. Knowledge cutoff: GPT-5.1 Chat Sep 30, 2024.

How do you decide the winner?

Each model gets a 0–100 score on capability (50%, independent benchmark results); price (25%, blended price per million tokens (3 input : 1 output), log scale); inputs & features (15%, image, PDF, audio and video input, tool calling, structured output and reasoning); context window (10%, maximum tokens per request, log scale). Dimensions missing for any model are dropped and the remaining weights rescaled, so every model is judged on the same evidence. Specs and prices come from public model listings and the labs’ own API pages; capability scores come from independent benchmark runs. Data updated Oct 4, 2026.

05 — Keep comparing

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