GPT-5.5 vs Grok 4.5
At a Glance
| Compare |  GPT-5.5OpenAI | Grok 4.5xAI |
|---|---|---|
| Intelligence, Cost, and Efficiency | ||
| IntelligenceHigher is better · MM Intelligence v2.5 | #7 of 4683.9 score · 3/3 sources · complete | #25 of 4660.1 score · 3/3 sources · complete |
| CostLower is better · Published-token output estimate | #38 of 44$0.341 per LiveBench case | #15 of 44$0.063 per LiveBench case |
| EfficiencyHigher is better · MM Efficiency v1.5 | #18 of 3853.4 score · 3/3 sources · complete | #11 of 3859.2 score · 3/3 sources · complete |
| Pricing and Limits | ||
| Input priceFrom · USD / 1M tokens | $5.00Openai ↗ · Sep 3, 2026 | $2.00Xai ↗ · Sep 3, 2026 |
| Output priceFrom · USD / 1M tokens | $30.00Openai ↗ · Sep 3, 2026 | $6.00Xai ↗ · Sep 3, 2026 |
| Context windowMaximum documented tokens | 1,050K | 500K |
| Model facts checked | Sep 3, 2026View model evidence → | Sep 3, 2026View model evidence → |
Token prices are the lowest available sourced USD rates; input and output may use different providers. Cost ranking estimates output spend on LiveBench, not a full request bill. Ranking methodology →
Available Benchmarks
| Benchmark | GPT-5.5 | Grok 4.5 |
|---|---|---|
| ARC-AGI-1verified-v1-ba05d69f6453 · verified_score · leader | 95.00100% of row best · percent · GPT-5.5 (XHigh) | 87.1792% of row best · percent · Grok 4.5 (Medium) |
| ARC-AGI-2verified-v2-6c676fa3e9af · verified_score · leader | 85.00100% of row best · percent · GPT-5.5 (XHigh) | 52.6462% of row best · percent · Grok 4.5 (Medium) |
| LMArena Agent Arenaagent-2026-09-15-d25aabda0010 · outcome_score · statistical tie | 2.67100% of row best · score · GPT 5.5; 95% CI [1.85777151, 3.48040109]; sessions 81254; observations 2107641; rank 20 | 2.92100% of row best · score · Grok 4.5; 95% CI [1.93207740, 3.90928463]; sessions 38146; observations 1942877; rank 19 |
| LMArena Document Arenadocument-2026-09-13-d25aabda0010 · arena_rating · leader | 1,484.48100% of row best · rating · gpt-5.5-high; 95% CI [1478.10008380, 1490.85597001]; votes 20944; rank 9 | 1,451.9698% of row best · rating · grok-4.5; 95% CI [1443.26182849, 1460.65626012]; votes 4965; rank 26 |
| LMArena Search Arenasearch-2026-08-24-d25aabda0010 · arena_rating · leader | 1,242.05100% of row best · rating · gpt-5.5-search; 95% CI [1236.73488085, 1247.37053078]; votes 89873; rank 3 | 1,212.6598% of row best · rating · grok-4.5; 95% CI [1205.78347274, 1219.50889748]; votes 31505; rank 8 |
| LMArena Text Arenatext-2026-09-13-d25aabda0010 · arena_rating · leader | 1,465.59100% of row best · rating · gpt-5.5; 95% CI [1461.82849712, 1469.35015015]; votes 66317; rank 31 | 1,450.1399% of row best · rating · grok-4.5; 95% CI [1445.44268767, 1454.81726995]; votes 30103; rank 45 |
| LMArena Vision Arenavision-2026-09-13-d25aabda0010 · arena_rating · statistical tie | 1,294.19100% of row best · rating · gpt-5.5-high; 95% CI [1287.85384790, 1300.52893287]; votes 21960; rank 20 | 1,288.54100% of row best · rating · grok-4.5; 95% CI [1280.47745270, 1296.60872281]; votes 8355; rank 24 |
| LiveBench2026-06-25 · overall · leader | 84.54100% of row best · percent · gpt-5.5-xhigh · 11,355 output tokens / case | 80.0195% of row best · percent · grok-4.5 · 10,517 output tokens / case |
| ToneBench2026-09-11-10-task-4ef099199c9c · overall_score · unverified | 82.60100% of row best · points · GPT-5.5 (xhigh) · 4,050 output tokens / case | 82.23100% of row best · points · Grok 4.5 · 2,688 output tokens / case |
| Overall ResultCounted from the protocol-matched rows above · 2 ties | 6 benchmark winsOverall lead | 0 benchmark wins |
Third-party benchmark Only like-for-like primary-publisher results are shown; raw scores, relative scores, configuration, and token spend remain visible.
Side-by-Side Facts
| Field | GPT-5.5 | Grok 4.5 |
|---|---|---|
| Developer | OpenAI | xAI |
| Family | Gpt 5 5 | Grok 4 |
| Model | GPT-5.5 | Grok 4.5 |
| Version | GPT-5.5 | Grok 4.5 |
| Lifecycle | active | active |
| Released | 2026-04-23 | 2026-07-16 |
| Knowledge cutoff | 2025-12-01 | Unknown |
| Input modalities | Text, Image | Text, Image |
| Output modalities | Text | Text |
| Context window | 1,050K | 500K |
| Total parameters | Unknown | Unknown |
| Active parameters | Unknown | Unknown |
| License | Unknown | Unknown |
| Open weights | No | No |
| API available | Yes | Yes |
| Self-hostable | No | No |
| Provider access | Openai (Standard), Openrouter (Standard) | Xai (Standard) |
| Capabilities | chat, generation, reasoning, structured_outputs, tools | chat, generation, reasoning, structured_outputs, tools |
GPT-5.5 Capabilities
Grok 4.5 Capabilities
Related Comparisons
All image comparisons →| A | Pair | B | Context |
|---|---|---|---|
GPT-5.5OpenAI | vs | GPT-6 AstraOpenAI | family variantsimage, text |
Claude Fable 5.1Anthropic | vs | GPT-5.5OpenAI | cross-developer peersimage, text |
 Gemini 3.1 ProGoogle DeepMind | vs | GPT-5.5OpenAI | cross-developer peerstext |
 DeepSeek-V4.1-FlashDeepSeek | vs | GPT-5.5OpenAI | cross-developer peersimage, text |
GPT-5.5OpenAI | vs | Grok 4.6xAI | cross-developer peersimage, text |
GPT-5.5OpenAI | vs |  Qwen3.8-MaxQwen | cross-developer peersimage, text |
 Kimi-K3Moonshot AI | vs | GPT-5.5OpenAI | cross-developer peersimage, text |
 MiniMax-M3MiniMax | vs | GPT-5.5OpenAI | cross-developer peersimage, text |
GPT-5.5OpenAI | vs |  GLM-5.3Z.ai | cross-developer peerstext |
GPT-5.5OpenAI | vs |  Hy4 previewTencent | cross-developer peerstext |
Seed 2.1 ProByteDance Seed | vs | GPT-5.5OpenAI | cross-developer peersimage, text |
 Mistral Large 3Mistral AI | vs | GPT-5.5OpenAI | cross-developer peersimage, text |
Primary Evidence
Sources and Freshness
Questions
GPT-5.5 vs Grok 4.5 FAQs
Is GPT-5.5 or Grok 4.5 better for coding?+
This comparison does not currently contain a protocol-matched coding benchmark for both GPT-5.5 and Grok 4.5, so Model Markets cannot name a coding leader from pricing, context size, or capability labels alone.
Which is cheaper, GPT-5.5 or Grok 4.5?+
GPT-5.5 is $5.00 and Grok 4.5 is $2.00 per million tokens, so Grok 4.5 is cheaper on this metric. GPT-5.5 is $30.00 and Grok 4.5 is $6.00 per million tokens, so Grok 4.5 is cheaper on this metric.
Which has a larger context window, GPT-5.5 or Grok 4.5?+
GPT-5.5 has the larger sourced context window. GPT-5.5 supports 1,050K and Grok 4.5 supports 500K.
Which performs better in benchmarks, GPT-5.5 or Grok 4.5?+
GPT-5.5 leads the current overall benchmark count. The result uses 8 protocol-matched benchmarks from 3 publishers; it is not a universal quality score.
Can GPT-5.5 or Grok 4.5 be self-hosted?+
Both models have the same recorded self-hosting status: unsupported. GPT-5.5 is not marked open weight; Grok 4.5 is not marked open weight.
Can GPT-5.5 and Grok 4.5 understand images?+
GPT-5.5 is documented with image input; Grok 4.5 is documented with image input. This reflects supported input modalities, not vision quality.
Which can generate longer answers, GPT-5.5 or Grok 4.5?+
Neither has a larger sourced maximum output. GPT-5.5 is 128K and Grok 4.5 is —.
Do GPT-5.5 and Grok 4.5 support reasoning and tool use?+
GPT-5.5: reasoning, tool calling, and image input. Grok 4.5: reasoning, tool calling, and image input. Feature support does not establish relative quality.
Which is available from more inference providers, GPT-5.5 or Grok 4.5?+
GPT-5.5 has 2 sourced provider routes; Grok 4.5 has 1, so GPT-5.5 has broader tracked availability.
Which offers better value, GPT-5.5 or Grok 4.5?+
There is no universal value winner. Compare the input and output prices above with the matched benchmark result for your workload: cheaper tokens can be offset by different quality, token usage, latency, or provider availability.