Model comparison
GPT-5.5 Pro vs Grok 4.6
OpenAI against xAI, compared on context, price, and verified benchmark results.
Catalog record checked September 3, 2026Individual provider fields may changeEvidence confidence: High — see receipts below
OpenAI
GPT-5.5 Pro
Frontier
xAI
Grok 4.6
Frontier
| Specification | GPT-5.5 Pro | Grok 4.6 |
|---|---|---|
| Provider | OpenAI | xAI |
| Tier | Frontier | Frontier |
| Context window | Winner: 1.05M | 500K |
| Max output | 128K | Winner: 131K |
| Input / 1M tokens | $30 | Winner: $2 |
| Output / 1M tokens | $180 | Winner: $6 |
| Weights | Closed | Closed |
| Parameters | Not disclosedUnverified | Not disclosedUnverified |
| Reasoning levels | none, low, medium, high, xhigh, max | low, medium, high, xhigh |
| Modalities | text, image | text, image |
| API model id | gpt-5.5-pro | grok-4.6 |
| Released | April 23, 2026 | August 12, 2026 |
| Artificial Analysis Intelligence Index [xhigh] (2026-08-14) | 60 | Not verifiedUnverified |
| Artificial Analysis Intelligence Index [high] (2026-08-14) | Not verifiedUnverified | 61 |
| Terminal-Bench 2.1 (2026-08-18) | Not verifiedUnverified | 88 |
| GPQA Diamond (2026-08-18) | Not verifiedUnverified | 94.9 |
Prices are USD per million tokens at standard rates, excluding batch and caching discounts. Bold indicates the better figure where one is objectively better. Values we could not confirm from the provider are shown as “Not verified” rather than estimated.
Benchmark receipts
- 2026-08-18: Artificial Analysis measurement (independent; tied 1st with Gemini 3.7 Flash high)Agentic terminal work: multi-step tasks executed in a sandboxed shell environment. Comparability: comparable with caveat — Scores across Terminal-Bench major versions (v1 vs v2) are NOT comparable; harness configuration (container, time limits) also shifts results.
- 2026-08-14: Artificial AnalysisComposite index blending reasoning, knowledge, and coding evals into one 0–100 score. Comparability: directly comparable — AA occasionally rebaselines the index scale between snapshots — a score captured on one date is only comparable to same-snapshot scores (check measuredAt).
Pricing tiers: GPT-5.5 Pro: Standard $30/$180 per MTok; no cached-input discount. Batch $15/$90. · Grok 4.6: $2/$6 per MTok (<200K prompt); $4/$12 (≥200K). Cached input $0.50/MTok. Knowledge cutoff Feb 1 2026.
GPT-5.5 Pro
GPT-5.5 Pro is OpenAI's highest-effort tier for maximal accuracy on the hardest tasks.
Best for
- Maximum-accuracy reasoning
- Research
- Hard enterprise workloads
Watch out
At $30/$180 per MTok it is the most expensive OpenAI tier; reserve for work that needs it.
Grok 4.6
Grok 4.6 is xAI's current flagship coding model, strong on LMArena WebDev.
Best for
- Coding agents
- Chat and knowledge
- Cost-sensitive frontier work
Watch out
Token rates double above a 200K-token prompt.
When the cheaper one wins
Grok 4.6 is cheaper on output at $6 per million tokens against $180 for GPT-5.5 Pro — about 30×. Use the cheaper tier for classification, extraction, summarisation, and any task where the expensive model’s extra score does not change the accepted output. The expensive one only pays if your hardest task actually fails on the cheap tier. These are standard-tier API rates, excluding batch and cache discounts.
Run the model pickerEvidence confidence: High
How strong and complete the evidence behind this comparison is — not a prediction of which model is better.
- Pricing verified on both sides — Input and output rates are verified for both models.
- 4/5 core specs verified on both sides — Not published for at least one side: parameter count.
- 1 shared named benchmark (scores match) — Measured on: Artificial Analysis Intelligence Index — scores are equivalent, so the benchmark does not separate the pair.
- Verified within the last 90 days — Newest catalog check was 8 days ago.
- Both models carry source citations — Each side has at least two catalog sources on record.
Source receipts
Each catalog figure was checked against the provider or an independent second source on the date shown.
- GPT-5.5 Pro: OpenAI — Introducing GPT-5.5 (accessed 2026-08-29)
- GPT-5.5 Pro: OpenAI API pricing (gpt-5.5-pro $30/$180) (accessed 2026-08-29)
- Grok 4.6: xAI — Grok 4.6 (accessed 2026-08-29)
- Grok 4.6: xAI pricing (grok-4.6 $2/$6, 500K) (accessed 2026-08-29)
Related comparisons
- Gemini 3.7 Flash vs Grok 4.6
- GPT-5.6 Luna vs Grok 4.6
- Claude Fable 5.1 vs GPT-5.5 Pro
- Claude Fable 5.1 vs Grok 4.6
- Claude Fable 5 vs GPT-5.5 Pro
- Claude Fable 5 vs Grok 4.6
Diving deeper on one model? GPT-5.5 Pro · Grok 4.6
Common questions
GPT-5.5 Pro vs Grok 4.6
Answered from the verified figures on this page rather than general guidance.
Is GPT-5.5 Pro or Grok 4.6 cheaper for input?
Grok 4.6 is cheaper at $2 per million input tokens, against $30 for GPT-5.5 Pro — roughly 15× the price. Output tokens usually dominate a real bill, so weigh the output rate more heavily than the input rate. These are base rates; GPT-5.5 Pro has tiered pricing: Standard $30/$180 per MTok; no cached-input discount. Batch $15/$90. Grok 4.6 has tiered pricing: $2/$6 per MTok (<200K prompt); $4/$12 (≥200K). Cached input $0.50/MTok. Knowledge cutoff Feb 1 2026.
Is GPT-5.5 Pro or Grok 4.6 cheaper for output?
Grok 4.6 is cheaper at $6 per million output tokens, against $180 for GPT-5.5 Pro — roughly 30× the price. Output tokens usually dominate a real bill, so weigh the output rate more heavily than the input rate. These are base rates; GPT-5.5 Pro has tiered pricing: Standard $30/$180 per MTok; no cached-input discount. Batch $15/$90. Grok 4.6 has tiered pricing: $2/$6 per MTok (<200K prompt); $4/$12 (≥200K). Cached input $0.50/MTok. Knowledge cutoff Feb 1 2026.
Which has the larger context window, GPT-5.5 Pro or Grok 4.6?
GPT-5.5 Pro accepts 1.05M tokens against 500K for Grok 4.6. This only matters if you routinely send very long documents or large codebases.
Do GPT-5.5 Pro and Grok 4.6 support the same reasoning levels?
GPT-5.5 Pro exposes none, low, medium, high, xhigh, max, while Grok 4.6 exposes low, medium, high, xhigh.
Should I use GPT-5.5 Pro or Grok 4.6?
Both sit in the frontier tier, so the choice usually comes down to price and context rather than capability. GPT-5.5 Pro suits maximum-accuracy reasoning; Grok 4.6 suits coding agents.
Next step
Choosing between them
The verified figures that separate this pair, computed from the catalog rather than restated boilerplate.
- Input price: Grok 4.6 costs $2 per 1M tokens versus $30 for GPT-5.5 Pro — a 15x difference at the headline tier.
- Context: GPT-5.5 Pro takes 1.05M against 500K for Grok 4.6 — only decisive if your prompts approach the smaller window.
- Measured capability: Grok 4.6 leads Artificial Analysis Intelligence Index 61 to 60 (measured 2026-08-14).
Choosing a harness rather than a model — Cursor, Copilot, Claude Code, Windsurf, or Lovable? Compare agentic harnesses · Latest releases.