Claude Opus 4.8 vs Grok 4.6 vs GPT-5.5
Too close to call on our weighted score (Grok 4.6 65, GPT-5.5 63, Claude Opus 4.8 63). The right pick depends on what you value most.
AnthropicClaude Opus 4.8
63/100- ECI158.3
- Price$5.00 / $25.00
- Context1M
xAIGrok 4.6
65/100- ECI156.6
- Price$2.00 / $6.00
- Context500K
OpenAIGPT-5.5
63/100- ECI159.2
- Price$5.00 / $30.00
- Context1.05M
Too close to call
It is close. Our weighted score puts them within 2 points (Grok 4.6 65/100, GPT-5.5 63/100, Claude Opus 4.8 63/100), so choose by what matters most for your work: GPT-5.5 for raw capability and Grok 4.6 on price. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.
- CapabilityGPT-5.5Capabilities Index (ECI): GPT-5.5 159.2 · Claude Opus 4.8 158.3 · Grok 4.6 156.6
- Lowest priceGrok 4.6Grok 4.6 $3.00 · Claude Opus 4.8 $10.00 · GPT-5.5 $11.25 per 1M tokens (3:1 blend)
- Longest contextGPT-5.5GPT-5.5 1,050,000 · Claude Opus 4.8 1,000,000 · Grok 4.6 500,000 tokens
- Widest inputsClaude Opus 4.8 and GPT-5.5Claude Opus 4.8: Text, Images, PDFs · Grok 4.6: Text, Images · GPT-5.5: Text, Images, PDFs
- Self-hostingNo open weightsAll three are available only through APIs
| Measure | Weight | Claude Opus 4.8 | Grok 4.6 | GPT-5.5 |
|---|---|---|---|---|
| CapabilityCapabilities Index (ECI) | 50% | 89 | 86 | 90 |
| Price | 25% | 2 | 27 | 0 |
| Inputs & features | 15% | 80 | 70 | 80 |
| Context window | 10% | 60 | 48 | 61 |
| Overall | 100% | 63/100 | 65/100 | 63/100 |
Every spec in one table
Highlighted cells lead their row. Dashes mean the data is not published.
| Specification | Claude Opus 4.8Anthropic | Grok 4.6xAI | GPT-5.5OpenAI |
|---|---|---|---|
| Capability | |||
| Capabilities Index (ECI) | 158.3 | 156.6 | 159.2 (best) |
| ECI rank | #12 of 148 | #19 of 148 | #10 of 148 (best) |
| GPQA DiamondGraduate-level science questions | 91.0% | 94.0% (best) | 94.0% (best) |
| FrontierMath Tiers 1–3Research-level mathematics | 80.0% | 66.0% | 85.3% (best) |
| OTIS Mock AIME 2024–2025Competition mathematics | 98.3% | 99.2% | 100% (best) |
| SWE-bench VerifiedFixing real GitHub issues | — | — | 80.6% |
| SimpleQA VerifiedShort factual questions | 53.0% | 49.3% | 63.0% (best) |
| Price per million tokens | |||
| Input | $5.00 | $2.00 (best) | $5.00 |
| Output | $25.00 | $6.00 (best) | $30.00 |
| Cached input | $0.50 | $0.50 | $0.50 |
| Blended (3:1) | $10.00 | $3.00 (best) | $11.25 |
| Long-context rate | Same rate | Over 200K: $4.00 / $12.00 | Over 272K: $10.00 / $45.00 |
| Price source | Official Anthropic API | Official xAI API | Official OpenAI API |
| Limits | |||
| Context window | 1,000,000 tokens | 500,000 tokens | 1,050,000 tokens (best) |
| Max output | 128,000 tokens | 500,000 tokens (best) | 128,000 tokens |
| Inputs and features | |||
| Text | Yes | Yes | Yes |
| Images | Yes | Yes | Yes |
| PDFs | Yes | No | Yes |
| Audio | No | No | No |
| Video | No | No | No |
| Reasoning | Yeslow · medium · high · xhigh · max | Yeslow · medium · high · xhigh | Yeslow · medium · high · xhigh |
| Tool calling | Yes | Yes | Yes |
| Structured output | Yes | Yes | Yes |
| Availability | |||
| Weights | Proprietary | Proprietary | Proprietary |
| API model ID | claude-opus-4-8 | grok-4.6 | gpt-5.5 |
| API providers | 45 (best) | 29 | 42 |
| Released | May 28, 2026 | Aug 12, 2026 | Apr 23, 2026 |
| Knowledge cutoff | Jan 2026 | Feb 1, 2026 | Dec 1, 2025 |
What would a month cost?
Enter your expected volume in millions of tokens. List prices only; caching and batch discounts would lower these.
- Claude Opus 4.8$100.00
- Grok 4.6$32.00
- GPT-5.5$110.00
Which should you choose?
Which is better: Claude Opus 4.8, Grok 4.6 or GPT-5.5?
It is close. Our weighted score puts them within 2 points (Grok 4.6 65/100, GPT-5.5 63/100, Claude Opus 4.8 63/100), so choose by what matters most for your work: GPT-5.5 for raw capability and Grok 4.6 on price. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.
Which is cheaper, Claude Opus 4.8, Grok 4.6 or GPT-5.5?
Grok 4.6 is cheaper at $2.00 input / $6.00 output per million tokens (official xAI API price). Claude Opus 4.8 costs $5.00 input / $25.00 output per million tokens (official Anthropic API price); GPT-5.5 costs $5.00 input / $30.00 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 4.6 versus $10.00 for Claude Opus 4.8 (3.3× as much) and $11.25 for GPT-5.5 (3.8× as much).
Which scores higher on benchmarks?
GPT-5.5 scores higher on the Capabilities Index (ECI): GPT-5.5 159.2 (#10 of 148), Claude Opus 4.8 158.3 (#12 of 148) and Grok 4.6 156.6 (#19 of 148). The confidence ranges of the top two overlap (156.9–162.4 vs 156.1–160.7), so treat the gap as small. On individual benchmarks: GPQA Diamond — Grok 4.6 94.0%, GPT-5.5 94.0%, Claude Opus 4.8 91.0%; FrontierMath Tiers 1–3 — GPT-5.5 85.3%, Claude Opus 4.8 80.0%, Grok 4.6 66.0%; OTIS Mock AIME 2024–2025 — GPT-5.5 100%, Grok 4.6 99.2%, Claude Opus 4.8 98.3%; SimpleQA Verified — GPT-5.5 63.0%, Claude Opus 4.8 53.0%, Grok 4.6 49.3%.
Which is better for coding?
There are no published SWE-bench Verified results for Claude Opus 4.8 and Grok 4.6 yet, so there is no like-for-like coding score. On overall capability, GPT-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-5.5 has the largest context window at 1,050,000 tokens, against 1,000,000 for Claude Opus 4.8 and 500,000 for Grok 4.6. Maximum output per response: Claude Opus 4.8 up to 128,000, Grok 4.6 up to 500,000, GPT-5.5 up to 128,000 tokens.
Which can read images, PDFs, audio or video?
Claude Opus 4.8 accepts text, images and PDFs; Grok 4.6 accepts text and images; GPT-5.5 accepts text, images and PDFs. Claude Opus 4.8 handles the widest range of inputs.
Are any of these open source?
No. Claude Opus 4.8, Grok 4.6 and GPT-5.5 are proprietary and only available through APIs and apps.
Which is newer?
Grok 4.6 is the newest, released Aug 12, 2026. Claude Opus 4.8 came out May 28, 2026; GPT-5.5 came out Apr 23, 2026. Knowledge cutoff: Claude Opus 4.8 Jan 2026, Grok 4.6 Feb 1, 2026, GPT-5.5 Dec 1, 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.
