ZMIME
Comparison · 3 models · Updated Oct 4, 2026

Claude Sonnet 5.5 vs Gemini 3.8 Flash vs GPT-6.1 Sol

Gemini 3.8 Flash comes out ahead, 73 to 69 and 65 on our weighted score, and it is the cheaper option too.

  1. Anthropic

    Claude Sonnet 5.5

    Released Sep 28, 2026

    65/100
    • ECI165.2
    • Price$2.00 / $10.00
    • Context1M
    Full specs Remove Claude Sonnet 5.5
  2. Our pick

    Google

    Gemini 3.8 Flash

    Released Sep 2, 2026

    73/100
    • ECI156.9
    • Price$0.75 / $3.75
    • Context1.05M
    Full specs Remove Gemini 3.8 Flash

  3. OpenAI

    GPT-6.1 Sol

    Released Sep 29, 2026

    69/100
    • ECI—
    • Price$2.00 / $10.00
    • Context1.05M
    Full specs Remove GPT-6.1 Sol
01 — Verdict

Gemini 3.8 Flash is our pick

Gemini 3.8 Flash is the better all-round choice, scoring 73/100 against GPT-6.1 Sol (69) and Claude Sonnet 5.5 (65). It leads on price and inputs & features. GPT-6.1 Sol wins on capability. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%. Capability uses the average of shared benchmarks (GPQA Diamond, FrontierMath Tiers 1–3, OTIS Mock AIME 2024–2025 and SimpleQA Verified), because GPT-6.1 Sol has no Capabilities Index score yet.

  • CapabilityGPT-6.1 SolShared benchmarks: GPT-6.1 Sol 90.7% · Gemini 3.8 Flash 83.1% · Claude Sonnet 5.5 82.7%
  • Lowest priceGemini 3.8 FlashGemini 3.8 Flash $1.50 · Claude Sonnet 5.5 $4.00 · GPT-6.1 Sol $4.00 per 1M tokens (3:1 blend)
  • Longest contextGPT-6.1 Sol and Gemini 3.8 FlashGPT-6.1 Sol 1,050,000 · Gemini 3.8 Flash 1,048,576 · Claude Sonnet 5.5 1,000,000 tokens
  • Widest inputsGemini 3.8 FlashClaude Sonnet 5.5: Text, Images, PDFs · Gemini 3.8 Flash: Text, Images, PDFs, Audio, Video · GPT-6.1 Sol: Text, Images, PDFs
  • Self-hostingNo open weightsAll three are available only through APIs
How the score is built
MeasureWeightClaude Sonnet 5.5Gemini 3.8 FlashGPT-6.1 Sol
CapabilityShared benchmarks50%838391
Price25%214221
Inputs & features15%8010080
Context window10%606161
Overall100%65/10073/10069/100
02 — Side by side

Every spec in one table

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

Claude Sonnet 5.5 vs Gemini 3.8 Flash vs GPT-6.1 Sol specifications side by side
SpecificationClaude Sonnet 5.5AnthropicGemini 3.8 FlashGoogleGPT-6.1 SolOpenAI
Capability
Capabilities Index (ECI)165.2 (best)156.9—
ECI rank#3 of 148 (best)#15 of 148—
GPQA DiamondGraduate-level science questions95.6% (best)95.4%95.4%
FrontierMath Tiers 1–3Research-level mathematics88.8%68.4%93.7% (best)
OTIS Mock AIME 2024–2025Competition mathematics100% (best)98.9%100% (best)
SimpleQA VerifiedShort factual questions46.5%69.7%73.9% (best)
Price per million tokens
Input$2.00$0.75 (best)$2.00
Output$10.00$3.75 (best)$10.00
Cached input$0.20$0.075 (best)$0.10
Blended (3:1)$4.00$1.50 (best)$4.00
Long-context rateSame rateSame rateOver 272K: $4.00 / $15.00
Price sourceOfficial Anthropic APIOfficial Google APIOfficial OpenAI API
Limits
Context window1,000,000 tokens1,048,576 tokens1,050,000 tokens (best)
Max output128,000 tokens (best)65,536 tokens128,000 tokens (best)
Inputs and features
TextYesYesYes
ImagesYesYesYes
PDFsYesYesYes
AudioNoYesNo
VideoNoYesNo
ReasoningYeslow · medium · high · xhigh · maxYeslow · medium · highYeslow · medium · high · xhigh · max
Tool callingYesYesYes
Structured outputYesYesYes
Availability
WeightsProprietaryProprietaryProprietary
API model IDclaude-sonnet-5-5gemini-3.8-flashgpt-6.1-sol
API providers23 (best)2121
ReleasedSep 28, 2026Sep 2, 2026Sep 29, 2026
Knowledge cutoffJun 2026—Apr 30, 2026
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.

  • Claude Sonnet 5.5$40.00
  • Gemini 3.8 Flash$15.00
  • GPT-6.1 Sol$40.00
04 — Questions

Which should you choose?

Which is better: Claude Sonnet 5.5, Gemini 3.8 Flash or GPT-6.1 Sol?

Gemini 3.8 Flash is the better all-round choice, scoring 73/100 against GPT-6.1 Sol (69) and Claude Sonnet 5.5 (65). It leads on price and inputs & features. GPT-6.1 Sol wins on capability. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%. Capability uses the average of shared benchmarks (GPQA Diamond, FrontierMath Tiers 1–3, OTIS Mock AIME 2024–2025 and SimpleQA Verified), because GPT-6.1 Sol has no Capabilities Index score yet.

Which is cheaper, Claude Sonnet 5.5, Gemini 3.8 Flash or GPT-6.1 Sol?

Gemini 3.8 Flash is cheaper at $0.75 input / $3.75 output per million tokens (official Google API price). Claude Sonnet 5.5 costs $2.00 input / $10.00 output per million tokens (official Anthropic API price); GPT-6.1 Sol costs $2.00 input / $10.00 output per million tokens (official OpenAI API price). At a typical mix of three input tokens to one output token, that is $1.50 per million tokens for Gemini 3.8 Flash versus $4.00 for Claude Sonnet 5.5 (2.7× as much) and $4.00 for GPT-6.1 Sol (2.7× as much).

Which scores higher on benchmarks?

Not every model here has a Capabilities Index score, so we compare the average of shared benchmarks (GPQA Diamond, FrontierMath Tiers 1–3, OTIS Mock AIME 2024–2025 and SimpleQA Verified): GPT-6.1 Sol 90.7%, Gemini 3.8 Flash 83.1% and Claude Sonnet 5.5 82.7%. On individual benchmarks: GPQA Diamond — Claude Sonnet 5.5 95.6%, Gemini 3.8 Flash 95.4%, GPT-6.1 Sol 95.4%; FrontierMath Tiers 1–3 — GPT-6.1 Sol 93.7%, Claude Sonnet 5.5 88.8%, Gemini 3.8 Flash 68.4%; OTIS Mock AIME 2024–2025 — Claude Sonnet 5.5 100%, GPT-6.1 Sol 100%, Gemini 3.8 Flash 98.9%; SimpleQA Verified — GPT-6.1 Sol 73.9%, Gemini 3.8 Flash 69.7%, Claude Sonnet 5.5 46.5%.

Which is better for coding?

There are no published SWE-bench Verified results for Claude Sonnet 5.5, Gemini 3.8 Flash and GPT-6.1 Sol yet, so there is no like-for-like coding score. On overall capability, GPT-6.1 Sol 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?

GPT-6.1 Sol and Gemini 3.8 Flash have the largest context windows (1,050,000 and 1,048,576 tokens), against 1,000,000 for Claude Sonnet 5.5. Maximum output per response: Claude Sonnet 5.5 up to 128,000, Gemini 3.8 Flash up to 65,536, GPT-6.1 Sol up to 128,000 tokens.

Which can read images, PDFs, audio or video?

Claude Sonnet 5.5 accepts text, images and PDFs; Gemini 3.8 Flash accepts text, images, PDFs, audio and video; GPT-6.1 Sol accepts text, images and PDFs. Gemini 3.8 Flash handles the widest range of inputs.

Are any of these open source?

No. Claude Sonnet 5.5, Gemini 3.8 Flash and GPT-6.1 Sol are proprietary and only available through APIs and apps.

Which is newer?

GPT-6.1 Sol is the newest, released Sep 29, 2026. Claude Sonnet 5.5 came out Sep 28, 2026; Gemini 3.8 Flash came out Sep 2, 2026. Knowledge cutoff: Claude Sonnet 5.5 Jun 2026, GPT-6.1 Sol Apr 30, 2026.

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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