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Comparison · 2 models · Updated Oct 4, 2026

Gemini 2.5 Flash vs Grok 4.20 (Reasoning)

Too close to call on our weighted score (Grok 4.20 (Reasoning) 68, Gemini 2.5 Flash 68). The right pick depends on what you value most.

  1. Google

    Gemini 2.5 Flash

    Released Jun 17, 2025

    68/100
    • ECI140.8
    • Price$0.30 / $2.50
    • Context1.05M
    Full specs Remove Gemini 2.5 Flash

  2. xAI

    Grok 4.20 (Reasoning)

    Released Mar 9, 2026

    68/100
    • ECI152.0
    • Price$1.25 / $2.50
    • Context1M
    Full specs Remove Grok 4.20 (Reasoning)

  3. Add a model

    Make it a three-way comparison.

01 — Verdict

Too close to call

It is close. Our weighted score puts them within a point (Grok 4.20 (Reasoning) 68/100, Gemini 2.5 Flash 68/100), so choose by what matters most for your work: Grok 4.20 (Reasoning) for raw capability, Gemini 2.5 Flash on price and Gemini 2.5 Flash for long inputs. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.

  • CapabilityGrok 4.20 (Reasoning)Capabilities Index (ECI): Grok 4.20 (Reasoning) 152.0 · Gemini 2.5 Flash 140.8
  • Lowest priceGemini 2.5 FlashGemini 2.5 Flash $0.85 · Grok 4.20 (Reasoning) $1.56 per 1M tokens (3:1 blend)
  • Longest contextGemini 2.5 FlashGemini 2.5 Flash 1,048,576 · Grok 4.20 (Reasoning) 1,000,000 tokens
  • Widest inputsGemini 2.5 FlashGemini 2.5 Flash: Text, Images, PDFs, Audio, Video · Grok 4.20 (Reasoning): Text, Images, PDFs
  • Self-hostingNo open weightsBoth are available only through APIs
How the score is built
MeasureWeightGemini 2.5 FlashGrok 4.20 (Reasoning)
CapabilityCapabilities Index (ECI)50%6781
Price25%5341
Inputs & features15%10080
Context window10%6160
Overall100%68/10068/100
02 — Side by side

Every spec in one table

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

Gemini 2.5 Flash vs Grok 4.20 (Reasoning) specifications side by side
SpecificationGemini 2.5 FlashGoogleGrok 4.20 (Reasoning)xAI
Capability
Capabilities Index (ECI)140.8152.0 (best)
ECI rank#97 of 148#41 of 148 (best)
GPQA DiamondGraduate-level science questions—89.3%
FrontierMath Tiers 1–3Research-level mathematics—44.9%
OTIS Mock AIME 2024–2025Competition mathematics—92.2%
SimpleQA VerifiedShort factual questions—30.2%
Price per million tokens
Input$0.30 (best)$1.25
Output$2.50$2.50
Cached input$0.03 (best)$0.20
Blended (3:1)$0.85 (best)$1.56
Long-context rateSame rateOver 200K: $2.50 / $5.00
Price sourceOfficial Google APIOfficial xAI API
Limits
Context window1,048,576 tokens (best)1,000,000 tokens
Max output65,536 tokens (best)30,000 tokens
Inputs and features
TextYesYes
ImagesYesYes
PDFsYesYes
AudioYesNo
VideoYesNo
ReasoningYesYes
Tool callingYesYes
Structured outputYesYes
Availability
WeightsProprietaryProprietary
API model IDgemini-2.5-flashgrok-4.20-0309-reasoning
API providers22 (best)11
ReleasedJun 17, 2025Mar 9, 2026
Knowledge cutoffJan 2025—
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.

  • Gemini 2.5 Flash$8.00
  • Grok 4.20 (Reasoning)$17.50
04 — Questions

Which should you choose?

Which is better: Gemini 2.5 Flash or Grok 4.20 (Reasoning)?

It is close. Our weighted score puts them within a point (Grok 4.20 (Reasoning) 68/100, Gemini 2.5 Flash 68/100), so choose by what matters most for your work: Grok 4.20 (Reasoning) for raw capability, Gemini 2.5 Flash on price and Gemini 2.5 Flash for long inputs. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.

Which is cheaper, Gemini 2.5 Flash or Grok 4.20 (Reasoning)?

Gemini 2.5 Flash is cheaper at $0.30 input / $2.50 output per million tokens (official Google API price). Grok 4.20 (Reasoning) costs $1.25 input / $2.50 output per million tokens (official xAI API price). At a typical mix of three input tokens to one output token, that is $0.85 per million tokens for Gemini 2.5 Flash versus $1.56 for Grok 4.20 (Reasoning) (1.8× as much).

Which scores higher on benchmarks?

Grok 4.20 (Reasoning) scores higher on the Capabilities Index (ECI): Grok 4.20 (Reasoning) 152.0 (#41 of 148) and Gemini 2.5 Flash 140.8 (#97 of 148). Their confidence ranges do not overlap (149.3–154.4 vs 138.5–142.3), so the gap is a real one.

Which is better for coding?

There are no published SWE-bench Verified results for Gemini 2.5 Flash and Grok 4.20 (Reasoning) yet, so there is no like-for-like coding score. On overall capability, Grok 4.20 (Reasoning) leads, which tends to carry over to coding, but test on your own codebase. Both support tool calling for agent workflows.

Which has the bigger context window?

Gemini 2.5 Flash has the largest context window at 1,048,576 tokens, against 1,000,000 for Grok 4.20 (Reasoning). Maximum output per response: Gemini 2.5 Flash up to 65,536, Grok 4.20 (Reasoning) up to 30,000 tokens.

Which can read images, PDFs, audio or video?

Gemini 2.5 Flash accepts text, images, PDFs, audio and video; Grok 4.20 (Reasoning) accepts text, images and PDFs. Gemini 2.5 Flash handles the widest range of inputs.

Are any of these open source?

No. Gemini 2.5 Flash and Grok 4.20 (Reasoning) are proprietary and only available through APIs and apps.

Which is newer?

Grok 4.20 (Reasoning) is the newest, released Mar 9, 2026. Gemini 2.5 Flash came out Jun 17, 2025. Knowledge cutoff: Gemini 2.5 Flash Jan 2025.

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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