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Comparison · 2 models · Updated Oct 4, 2026

Claude Sonnet 5.5 vs Gemini 3.8 Flash

Too close to call on our weighted score (Gemini 3.8 Flash 75, Claude Sonnet 5.5 72). The right pick depends on what you value most.

  1. Anthropic

    Claude Sonnet 5.5

    Released Sep 28, 2026

    72/100
    • ECI165.2
    • Price$2.00 / $10.00
    • Context1M
    Full specs Remove Claude Sonnet 5.5

  2. Google

    Gemini 3.8 Flash

    Released Sep 2, 2026

    75/100
    • ECI156.9
    • Price$0.75 / $3.75
    • Context1.05M
    Full specs Remove Gemini 3.8 Flash

  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 3 points (Gemini 3.8 Flash 75/100, Claude Sonnet 5.5 72/100), so choose by what matters most for your work: Claude Sonnet 5.5 for raw capability, Gemini 3.8 Flash on price and Gemini 3.8 Flash for long inputs. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.

  • CapabilityClaude Sonnet 5.5Capabilities Index (ECI): Claude Sonnet 5.5 165.2 · Gemini 3.8 Flash 156.9
  • Lowest priceGemini 3.8 FlashGemini 3.8 Flash $1.50 · Claude Sonnet 5.5 $4.00 per 1M tokens (3:1 blend)
  • Longest contextGemini 3.8 FlashGemini 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
  • Self-hostingNo open weightsBoth are available only through APIs
How the score is built
MeasureWeightClaude Sonnet 5.5Gemini 3.8 Flash
CapabilityCapabilities Index (ECI)50%9787
Price25%2142
Inputs & features15%80100
Context window10%6061
Overall100%72/10075/100
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 specifications side by side
SpecificationClaude Sonnet 5.5AnthropicGemini 3.8 FlashGoogle
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%
FrontierMath Tiers 1–3Research-level mathematics88.8% (best)68.4%
OTIS Mock AIME 2024–2025Competition mathematics100% (best)98.9%
SimpleQA VerifiedShort factual questions46.5%69.7% (best)
Price per million tokens
Input$2.00$0.75 (best)
Output$10.00$3.75 (best)
Cached input$0.20$0.075 (best)
Blended (3:1)$4.00$1.50 (best)
Long-context rateSame rateSame rate
Price sourceOfficial Anthropic APIOfficial Google API
Limits
Context window1,000,000 tokens1,048,576 tokens (best)
Max output128,000 tokens (best)65,536 tokens
Inputs and features
TextYesYes
ImagesYesYes
PDFsYesYes
AudioNoYes
VideoNoYes
ReasoningYeslow · medium · high · xhigh · maxYeslow · medium · high
Tool callingYesYes
Structured outputYesYes
Availability
WeightsProprietaryProprietary
API model IDclaude-sonnet-5-5gemini-3.8-flash
API providers23 (best)21
ReleasedSep 28, 2026Sep 2, 2026
Knowledge cutoffJun 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
04 — Questions

Which should you choose?

Which is better: Claude Sonnet 5.5 or Gemini 3.8 Flash?

It is close. Our weighted score puts them within 3 points (Gemini 3.8 Flash 75/100, Claude Sonnet 5.5 72/100), so choose by what matters most for your work: Claude Sonnet 5.5 for raw capability, Gemini 3.8 Flash on price and Gemini 3.8 Flash for long inputs. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.

Which is cheaper, Claude Sonnet 5.5 or Gemini 3.8 Flash?

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). 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).

Which scores higher on benchmarks?

Claude Sonnet 5.5 scores higher on the Capabilities Index (ECI): Claude Sonnet 5.5 165.2 (#3 of 148) and Gemini 3.8 Flash 156.9 (#15 of 148). Their confidence ranges do not overlap (161.8–169.4 vs 154.6–160.4), so the gap is a real one. On individual benchmarks: GPQA Diamond — Claude Sonnet 5.5 95.6%, Gemini 3.8 Flash 95.4%; FrontierMath Tiers 1–3 — Claude Sonnet 5.5 88.8%, Gemini 3.8 Flash 68.4%; OTIS Mock AIME 2024–2025 — Claude Sonnet 5.5 100%, Gemini 3.8 Flash 98.9%; SimpleQA Verified — 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 and Gemini 3.8 Flash yet, so there is no like-for-like coding score. On overall capability, Claude Sonnet 5.5 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 3.8 Flash has the largest context window at 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 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. Gemini 3.8 Flash handles the widest range of inputs.

Are any of these open source?

No. Claude Sonnet 5.5 and Gemini 3.8 Flash are proprietary and only available through APIs and apps.

Which is newer?

Claude Sonnet 5.5 is the newest, released Sep 28, 2026. Gemini 3.8 Flash came out Sep 2, 2026. Knowledge cutoff: Claude Sonnet 5.5 Jun 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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