ZMIME
Comparison · 2 models · Updated Nov 2, 2026

GPT-6.1 Terra vs Claude Sonnet 5.5

GPT-6.1 Terra comes out ahead, 76 to 72 on our weighted score, and it is the cheaper option too.

  1. Our pick

    OpenAI

    GPT-6.1 Terra

    Released Oct 26, 2026

    76/100
    • ECI168.1
    • Price$1.00 / $5.00
    • Context1.05M
    Full specs Remove GPT-6.1 Terra

  2. Anthropic

    Claude Sonnet 5.5

    Released Sep 28, 2026

    72/100
    • ECI166.7
    • Price$2.00 / $10.00
    • Context1M
    Full specs Remove Claude Sonnet 5.5

  3. Add a model

    Make it a three-way comparison.

01 — Verdict

GPT-6.1 Terra is our pick

GPT-6.1 Terra is the better all-round choice, scoring 76/100 against Claude Sonnet 5.5 (72). It leads on capability and price. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.

  • CapabilityGPT-6.1 TerraCapabilities Index (ECI): GPT-6.1 Terra 168.1 · Claude Sonnet 5.5 166.7
  • Lowest priceGPT-6.1 TerraGPT-6.1 Terra $2.00 · Claude Sonnet 5.5 $4.00 per 1M tokens (3:1 blend)
  • Longest contextGPT-6.1 TerraGPT-6.1 Terra 1,050,000 · Claude Sonnet 5.5 1,000,000 tokens
  • Widest inputsSame inputsGPT-6.1 Terra: Text, Images, PDFs · Claude Sonnet 5.5: Text, Images, PDFs
  • Self-hostingNo open weightsBoth are available only through APIs
How the score is built
MeasureWeightGPT-6.1 TerraClaude Sonnet 5.5
CapabilityCapabilities Index (ECI)50%9997
Price25%3420
Inputs & features15%8080
Context window10%6160
Overall100%76/10072/100
02 — Side by side

Every spec in one table

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

GPT-6.1 Terra vs Claude Sonnet 5.5 specifications side by side
SpecificationGPT-6.1 TerraOpenAIClaude Sonnet 5.5Anthropic
Capability
Capabilities Index (ECI)168.1 (best)166.7
ECI rank#3 of 165 (best)#5 of 165
GPQA DiamondGraduate-level science questions94.3%95.6% (best)
FrontierMath Tiers 1–3Research-level mathematics90.9% (best)88.8%
OTIS Mock AIME 2024–2025Competition mathematics100%100%
SimpleQA VerifiedShort factual questions57.3% (best)46.5%
Price per million tokens
Input$1.00 (best)$2.00
Output$5.00 (best)$10.00
Cached input$0.05 (best)$0.10
Blended (3:1)$2.00 (best)$4.00
Long-context rateOver 272K: $2.00 / $7.50Same rate
Price sourceOfficial OpenAI APIOfficial Anthropic API
Limits
Context window1,050,000 tokens (best)1,000,000 tokens
Max output128,000 tokens128,000 tokens
Inputs and features
TextYesYes
ImagesYesYes
PDFsYesYes
AudioNoNo
VideoNoNo
ReasoningYeslow · medium · high · xhigh · maxYeslow · medium · high · xhigh · max
Tool callingYesYes
Structured outputYesYes
Availability
WeightsProprietaryProprietary
API model IDgpt-6.1-terraclaude-sonnet-5-5
API providers2234 (best)
ReleasedOct 26, 2026Sep 28, 2026
Knowledge cutoffJun 1, 2026Jun 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.

  • GPT-6.1 Terra$20.00
  • Claude Sonnet 5.5$40.00
04 — Questions

Which should you choose?

Which is better: GPT-6.1 Terra or Claude Sonnet 5.5?

GPT-6.1 Terra is the better all-round choice, scoring 76/100 against Claude Sonnet 5.5 (72). It leads on capability and price. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.

Which is cheaper, GPT-6.1 Terra or Claude Sonnet 5.5?

GPT-6.1 Terra is cheaper at $1.00 input / $5.00 output per million tokens (official OpenAI 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 $2.00 per million tokens for GPT-6.1 Terra versus $4.00 for Claude Sonnet 5.5 (2× as much).

Which scores higher on benchmarks?

GPT-6.1 Terra scores higher on the Capabilities Index (ECI): GPT-6.1 Terra 168.1 (#3 of 165) and Claude Sonnet 5.5 166.7 (#5 of 165). The confidence ranges of the top two overlap (164.9–172.9 vs 163.6–171.3), so treat the gap as small. On individual benchmarks: GPQA Diamond — Claude Sonnet 5.5 95.6%, GPT-6.1 Terra 94.3%; FrontierMath Tiers 1–3 — GPT-6.1 Terra 90.9%, Claude Sonnet 5.5 88.8%; OTIS Mock AIME 2024–2025 — GPT-6.1 Terra 100%, Claude Sonnet 5.5 100%; SimpleQA Verified — GPT-6.1 Terra 57.3%, Claude Sonnet 5.5 46.5%.

Which is better for coding?

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

GPT-6.1 Terra has the largest context window at 1,050,000 tokens, against 1,000,000 for Claude Sonnet 5.5. Maximum output per response: GPT-6.1 Terra up to 128,000, Claude Sonnet 5.5 up to 128,000 tokens.

Which can read images, PDFs, audio or video?

GPT-6.1 Terra accepts text, images and PDFs; Claude Sonnet 5.5 accepts text, images and PDFs. They handle the same number of input types.

Are any of these open source?

No. GPT-6.1 Terra and Claude Sonnet 5.5 are proprietary and only available through APIs and apps.

Which is newer?

GPT-6.1 Terra is the newest, released Oct 26, 2026. Claude Sonnet 5.5 came out Sep 28, 2026. Knowledge cutoff: GPT-6.1 Terra Jun 1, 2026, 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 Nov 2, 2026.

05 — Keep comparing

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