GPT-6.1 Terra vs Claude Opus 5.5 vs Claude Sonnet 5.5
GPT-6.1 Terra comes out ahead, 76 to 72 and 69 on our weighted score, and it is the cheaper option too.
- Our pick
OpenAIGPT-6.1 Terra
76/100- ECI168.1
- Price$1.00 / $5.00
- Context1.05M
AnthropicClaude Opus 5.5
69/100- ECI168.4
- Price$4.00 / $20.00
- Context1M
- Anthropic
Claude Sonnet 5.5
72/100- ECI166.7
- Price$2.00 / $10.00
- Context1M
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) and Claude Opus 5.5 (69). It leads on price. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.
- CapabilityClaude Opus 5.5Capabilities Index (ECI): Claude Opus 5.5 168.4 · 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 · Claude Opus 5.5 $8.00 per 1M tokens (3:1 blend)
- Longest contextGPT-6.1 TerraGPT-6.1 Terra 1,050,000 · Claude Opus 5.5 1,000,000 · Claude Sonnet 5.5 1,000,000 tokens
- Widest inputsSame inputsGPT-6.1 Terra: Text, Images, PDFs · Claude Opus 5.5: Text, Images, PDFs · Claude Sonnet 5.5: Text, Images, PDFs
- Self-hostingNo open weightsAll three are available only through APIs
| Measure | Weight | GPT-6.1 Terra | Claude Opus 5.5 | Claude Sonnet 5.5 |
|---|---|---|---|---|
| CapabilityCapabilities Index (ECI) | 50% | 99 | 99 | 97 |
| Price | 25% | 34 | 7 | 20 |
| Inputs & features | 15% | 80 | 80 | 80 |
| Context window | 10% | 61 | 60 | 60 |
| Overall | 100% | 76/100 | 69/100 | 72/100 |
Every spec in one table
Highlighted cells lead their row. Dashes mean the data is not published.
| Specification | GPT-6.1 TerraOpenAI | Claude Opus 5.5Anthropic | Claude Sonnet 5.5Anthropic |
|---|---|---|---|
| Capability | |||
| Capabilities Index (ECI) | 168.1 | 168.4 (best) | 166.7 |
| ECI rank | #3 of 165 | #2 of 165 (best) | #5 of 165 |
| GPQA DiamondGraduate-level science questions | 94.3% | 90.6% | 95.6% (best) |
| FrontierMath Tiers 1–3Research-level mathematics | 90.9% | 91.2% (best) | 88.8% |
| OTIS Mock AIME 2024–2025Competition mathematics | 100% | 100% | 100% |
| SimpleQA VerifiedShort factual questions | 57.3% | 72.2% (best) | 46.5% |
| Price per million tokens | |||
| Input | $1.00 (best) | $4.00 | $2.00 |
| Output | $5.00 (best) | $20.00 | $10.00 |
| Cached input | $0.05 (best) | $0.20 | $0.10 |
| Blended (3:1) | $2.00 (best) | $8.00 | $4.00 |
| Long-context rate | Over 272K: $2.00 / $7.50 | Same rate | Same rate |
| Price source | Official OpenAI API | Official Anthropic API | Official Anthropic API |
| Limits | |||
| Context window | 1,050,000 tokens (best) | 1,000,000 tokens | 1,000,000 tokens |
| Max output | 128,000 tokens | 128,000 tokens | 128,000 tokens |
| Inputs and features | |||
| Text | Yes | Yes | Yes |
| Images | Yes | Yes | Yes |
| PDFs | Yes | Yes | Yes |
| Audio | No | No | No |
| Video | No | No | No |
| Reasoning | Yeslow · medium · high · xhigh · max | Yeslow · medium · high · xhigh · max | Yeslow · medium · high · xhigh · max |
| Tool calling | Yes | Yes | Yes |
| Structured output | Yes | Yes | Yes |
| Availability | |||
| Weights | Proprietary | Proprietary | Proprietary |
| API model ID | gpt-6.1-terra | claude-opus-5-5 | claude-sonnet-5-5 |
| API providers | 22 | 36 (best) | 34 |
| Released | Oct 26, 2026 | Sep 22, 2026 | Sep 28, 2026 |
| Knowledge cutoff | Jun 1, 2026 | Jun 2026 | Jun 2026 |
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 Opus 5.5$80.00
- Claude Sonnet 5.5$40.00
Which should you choose?
Which is better: GPT-6.1 Terra, Claude Opus 5.5 or Claude Sonnet 5.5?
GPT-6.1 Terra is the better all-round choice, scoring 76/100 against Claude Sonnet 5.5 (72) and Claude Opus 5.5 (69). It leads on price. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.
Which is cheaper, GPT-6.1 Terra, Claude Opus 5.5 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); Claude Opus 5.5 costs $4.00 input / $20.00 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) and $8.00 for Claude Opus 5.5 (4× as much).
Which scores higher on benchmarks?
Claude Opus 5.5 scores higher on the Capabilities Index (ECI): Claude Opus 5.5 168.4 (#2 of 165), 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 (165.4–173.0 vs 164.9–172.9), so treat the gap as small. On individual benchmarks: GPQA Diamond — Claude Sonnet 5.5 95.6%, GPT-6.1 Terra 94.3%, Claude Opus 5.5 90.6%; FrontierMath Tiers 1–3 — Claude Opus 5.5 91.2%, GPT-6.1 Terra 90.9%, Claude Sonnet 5.5 88.8%; OTIS Mock AIME 2024–2025 — GPT-6.1 Terra 100%, Claude Opus 5.5 100%, Claude Sonnet 5.5 100%; SimpleQA Verified — Claude Opus 5.5 72.2%, 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, Claude Opus 5.5 and Claude Sonnet 5.5 yet, so there is no like-for-like coding score. On overall capability, Claude Opus 5.5 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 Terra has the largest context window at 1,050,000 tokens, against 1,000,000 for Claude Opus 5.5 and 1,000,000 for Claude Sonnet 5.5. Maximum output per response: GPT-6.1 Terra up to 128,000, Claude Opus 5.5 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 Opus 5.5 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, Claude Opus 5.5 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; Claude Opus 5.5 came out Sep 22, 2026. Knowledge cutoff: GPT-6.1 Terra Jun 1, 2026, Claude Opus 5.5 Jun 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.
