ZMIME
Comparison · 3 models · Updated Oct 4, 2026

Grok 4.5 vs GPT-5.3 Codex vs Gemini 3.5 Flash

Gemini 3.5 Flash comes out ahead, 69 to 64 and 64 on our weighted score, though Grok 4.5 is 11% cheaper per token.

  1. xAI

    Grok 4.5

    Released Jul 8, 2026

    64/100
    • ECI154.0
    • Price$2.00 / $6.00
    • Context500K
    Full specs Remove Grok 4.5

  2. OpenAI

    GPT-5.3 Codex

    Released Feb 5, 2026

    64/100
    • ECI156.8
    • Price$1.75 / $14.00
    • Context400K
    Full specs Remove GPT-5.3 Codex
  3. Our pick

    Google

    Gemini 3.5 Flash

    Released May 19, 2026

    69/100
    • ECI154.5
    • Price$1.50 / $9.00
    • Context1.05M
    Full specs Remove Gemini 3.5 Flash
01 — Verdict

Gemini 3.5 Flash is our pick

Gemini 3.5 Flash is the better all-round choice, scoring 69/100 against GPT-5.3 Codex (64) and Grok 4.5 (64). It leads on inputs & features and context window. Grok 4.5 wins on price. GPT-5.3 Codex wins on capability. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.

  • CapabilityGPT-5.3 CodexCapabilities Index (ECI): GPT-5.3 Codex 156.8 · Gemini 3.5 Flash 154.5 · Grok 4.5 154.0
  • Lowest priceGrok 4.5Grok 4.5 $3.00 · Gemini 3.5 Flash $3.38 · GPT-5.3 Codex $4.81 per 1M tokens (3:1 blend)
  • Longest contextGemini 3.5 FlashGemini 3.5 Flash 1,048,576 · Grok 4.5 500,000 · GPT-5.3 Codex 400,000 tokens
  • Widest inputsGemini 3.5 FlashGrok 4.5: Text, Images · GPT-5.3 Codex: Text, Images, PDFs · Gemini 3.5 Flash: Text, Images, PDFs, Audio, Video
  • Self-hostingNo open weightsAll three are available only through APIs
How the score is built
MeasureWeightGrok 4.5GPT-5.3 CodexGemini 3.5 Flash
CapabilityCapabilities Index (ECI)50%838784
Price25%271825
Inputs & features15%7080100
Context window10%484461
Overall100%64/10064/10069/100
02 — Side by side

Every spec in one table

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

Grok 4.5 vs GPT-5.3 Codex vs Gemini 3.5 Flash specifications side by side
SpecificationGrok 4.5xAIGPT-5.3 CodexOpenAIGemini 3.5 FlashGoogle
Capability
Capabilities Index (ECI)154.0156.8 (best)154.5
ECI rank#36 of 148#18 of 148 (best)#33 of 148
GPQA DiamondGraduate-level science questions93.4% (best)—92.8%
FrontierMath Tiers 1–3Research-level mathematics57.2%—62.8% (best)
OTIS Mock AIME 2024–2025Competition mathematics97.8% (best)—95.6%
SWE-bench VerifiedFixing real GitHub issues—74.8%79.3% (best)
SimpleQA VerifiedShort factual questions48.3%—66.2% (best)
Price per million tokens
Input$2.00$1.75$1.50 (best)
Output$6.00 (best)$14.00$9.00
Cached input$0.30$0.175$0.15 (best)
Blended (3:1)$3.00 (best)$4.81$3.38
Long-context rateOver 200K: $4.00 / $12.00Same rateSame rate
Price sourceOfficial xAI APIOfficial OpenAI APIOfficial Google API
Limits
Context window500,000 tokens400,000 tokens1,048,576 tokens (best)
Max output500,000 tokens (best)128,000 tokens65,536 tokens
Inputs and features
TextYesYesYes
ImagesYesYesYes
PDFsNoYesYes
AudioNoNoYes
VideoNoNoYes
ReasoningYeslow · medium · highYeslow · medium · high · xhighYesminimal · low · medium · high
Tool callingYesYesYes
Structured outputYesYesYes
Availability
WeightsProprietaryProprietaryProprietary
API model IDgrok-4.5gpt-5.3-codexgemini-3.5-flash
API providers241932 (best)
ReleasedJul 8, 2026Feb 5, 2026May 19, 2026
Knowledge cutoff—Aug 31, 2025Jan 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.

  • Grok 4.5$32.00
  • GPT-5.3 Codex$45.50
  • Gemini 3.5 Flash$33.00
04 — Questions

Which should you choose?

Which is better: Grok 4.5, GPT-5.3 Codex or Gemini 3.5 Flash?

Gemini 3.5 Flash is the better all-round choice, scoring 69/100 against GPT-5.3 Codex (64) and Grok 4.5 (64). It leads on inputs & features and context window. Grok 4.5 wins on price. GPT-5.3 Codex wins on capability. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.

Which is cheaper, Grok 4.5, GPT-5.3 Codex or Gemini 3.5 Flash?

Grok 4.5 is cheaper at $2.00 input / $6.00 output per million tokens (official xAI API price). Gemini 3.5 Flash costs $1.50 input / $9.00 output per million tokens (official Google API price); GPT-5.3 Codex costs $1.75 input / $14.00 output per million tokens (official OpenAI API price). At a typical mix of three input tokens to one output token, that is $3.00 per million tokens for Grok 4.5 versus $3.38 for Gemini 3.5 Flash (1.1× as much) and $4.81 for GPT-5.3 Codex (1.6× as much).

Which scores higher on benchmarks?

GPT-5.3 Codex scores higher on the Capabilities Index (ECI): GPT-5.3 Codex 156.8 (#18 of 148), Gemini 3.5 Flash 154.5 (#33 of 148) and Grok 4.5 154.0 (#36 of 148). The confidence ranges of the top two overlap (153.5–160.8 vs 152.5–156.6), so treat the gap as small.

Which is better for coding?

There are no published SWE-bench Verified results for Grok 4.5 yet, so there is no like-for-like coding score. On overall capability, GPT-5.3 Codex leads, which tends to carry over to coding, but test on your own codebase. All three support tool calling for agent workflows.

Which has the bigger context window?

Gemini 3.5 Flash has the largest context window at 1,048,576 tokens, against 500,000 for Grok 4.5 and 400,000 for GPT-5.3 Codex. Maximum output per response: Grok 4.5 up to 500,000, GPT-5.3 Codex up to 128,000, Gemini 3.5 Flash up to 65,536 tokens.

Which can read images, PDFs, audio or video?

Grok 4.5 accepts text and images; GPT-5.3 Codex accepts text, images and PDFs; Gemini 3.5 Flash accepts text, images, PDFs, audio and video. Gemini 3.5 Flash handles the widest range of inputs.

Are any of these open source?

No. Grok 4.5, GPT-5.3 Codex and Gemini 3.5 Flash are proprietary and only available through APIs and apps.

Which is newer?

Grok 4.5 is the newest, released Jul 8, 2026. Gemini 3.5 Flash came out May 19, 2026; GPT-5.3 Codex came out Feb 5, 2026. Knowledge cutoff: GPT-5.3 Codex Aug 31, 2025, Gemini 3.5 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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