LLM Comparison

GPT-5.5 Pro vs Grok 4.20

Side-by-side specs, pricing & capabilities · Updated October 2026

Price vs Intelligence

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2/6 models

Same tier:

	GPT-5.5 Pro	Grok 4.20
Organization	OpenAI	xAI
OpenTools Score	95 0.9	72 18.1
Family	GPT	Grok
Status	Current	Current
Release Date	Apr 2026	Mar 2026
Context Window	1.1M tokens	2.0M tokens
Input Price	$30.00/M tokens	$2.00/M tokens
Output Price	$180.00/M tokens	$6.00/M tokens
Pricing Notes	No cached input discount. Long context (>272K tokens): 2x input, 1.5x output. Batch API: 50% discount. Regional processing: 10% uplift.	Cache read: $0.2000/M tokens
Capabilities	textvisioncodetool-useextended-thinkingweb-search	textvisioncode
Training Cutoff	Dec 01, 2025	—
Max Output	128K tokens	—
API Identifier	`openai/gpt-5.5-pro`	`x-ai/grok-4.20`
Benchmarks
FrontierMath Tier 4	39.6openai	—
FrontierMath Tier 1-3	52.4openai	—
HLE (with tools)	57.2openai	—
HLE (no tools)	43.1openai	—
BrowseComp	90.1openai	—
GeneBench	33.2openai	—
GDPval	82.3openai	—
Investment Banking Modeling	88.6openai	—
GPQA Diamond	—	91.1111artificial-analysis
	View GPT-5.5 Pro	View Grok 4.20

Cost Calculator

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Input tokens / month

Output tokens / month

Model	Input	Output	Total / mo	vs Best
Grok 4.20Cheapest	$2.00	$3.00	$5.00	—
GPT-5.5 Pro	$30.00	$90.00	$120.00	+2300%

OpenAI

GPT-5.5 Pro

GPT-5.5 Pro uses more compute to think harder and provide consistently better answers than GPT-5.5. Designed for the toughest problems, some requests may take several minutes. It excels at FrontierMath Tier 4 (39.6%) and BrowseComp (90.1%), offering the highest intelligence available from OpenAI at a premium price point.

xAI

Grok 4.20

Grok 4.20 is a multimodal llm from xAI. Supports up to 2,000,000 token context window. Available from $2.00/M input tokens.