o3-pro vs Grok 4.20 (Reasoning)
Benchmarks, API Token Pricing, Context Window & Speed Comparison
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o3-pro by OpenAI and Grok 4.20 (Reasoning) by xAI represent two of the frontier AI models analyzed in our comprehensive 2026 AI benchmark and LLM comparison. In this head-to-head evaluation, we examine API token pricing, context window specifications, inference speed (tokens per second), and empirical reasoning performance. From a pure economic perspective, Grok 4.20 (Reasoning) holds a notable pricing advantage for token ingestion. On output generation, Grok 4.20 (Reasoning) is more economical per million generated tokens. In data-heavy architectures requiring extensive repository or document analysis, Grok 4.20 (Reasoning) provides an expanded memory horizon with 1,000K tokens. In latency-sensitive production environments, Grok 4.20 (Reasoning) leads in tokens-per-second throughput, making it ideal for real-time conversational agents and high-concurrency workflows. Below is the complete empirical head-to-head breakdown across cost, speed, context, and capability matrices.
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o3-pro
High-Effort o3A maximum-effort o3 tier built for the hardest technical questions and deep analysis.
$20.00 / 1M
$80.00 / 1M
200K tokens
71.5%
Grok 4.20 (Reasoning)
Document AnalysisxAI's reasoning model engineered for heavy document analysis, complex logic deduction, and long-horizon agentic tool use.
$3.00 / 1M
$15.00 / 1M
1M tokens
68.2%
Key Differences at a Glance
- Grok 4.20 (Reasoning) is 5.7x cheaper for API usage (input + output tokens combined).
- Grok 4.20 (Reasoning) has a larger context window (1M vs 200K tokens).
- Grok 4.20 (Reasoning) is faster at 95 tok/s vs 30 tok/s.
- o3-pro leads on SWE-bench coding (71.5% vs 68.2%).
| Feature | o3-pro | Grok 4.20 (Reasoning) |
|---|---|---|
Intelligence Index Composite reasoning & knowledge score (0-100) | 58 | 68 |
Provider | OpenAI | xAI |
Input Price Cost per million input tokens | $20.00 / 1M | $3.00 / 1M |
Output Price Cost per million output tokens | $80.00 / 1M | $15.00 / 1M |
Blended Price Weighted 7:2:1 cache:input:output per 1M | $15.50 / 1M | $2.63 / 1M |
Context Window Maximum input + output tokens | 200K tokens~300 A4 pages of text | 1M tokens~1,500 A4 pages of text |
Max Output Tokens Per single request | 100K | 66K |
Throughput Speed Tokens generated per second | 30 tok/s | 95 tok/s |
SWE-bench Verified Real-world software engineering | 71.5% | 68.2% |
GPQA Diamond Graduate-level reasoning | 79.5% | 72.8% |
Cached Input Price Prompt caching discount per 1M tokens | $5.00 / 1M | $0.75 / 1M |
Who Wins Where?
At-a-glance decision frameworkEmpirical Head-to-Head Benchmark Scores
Official evaluation metrics verified by independent third-party research labs.
Industry benchmark evaluating real-world GitHub issue resolution and multi-file debugging.
Challenging questions created by domain experts to test complex PhD-level reasoning.
Hardened reasoning and academic knowledge benchmark with reduced lucky-guess probability.
Crowdsourced human preference evaluation based on blind, head-to-head model battles.
Extremely difficult, closed-ended questions spanning the frontier of human expert knowledge.
Autonomous multi-step tasks executed inside a real command-line terminal environment.
Research-grade coding problems drawn from real scientific and numerical workloads.
Contamination-free competitive programming problems collected continuously over time.
American Invitational Mathematics Examination — multi-step Olympiad-level reasoning.
Accuracy when reasoning over very large inputs that fill the model context window.
Tokens emitted per second during active generation streaming.
Latency & Response Time
Time to first token (TTFT) and estimated end-to-end response time for a typical 500-token response.
Real-Time Interactive Token Cost Simulator
Adjust sliders to calculate projected monthly cloud API spending with prompt caching discounts.
o3-pro · Strengths & Key Advantages
- More accurate than o3 on genuinely hard reasoning problems
- Excellent for verifiable, high-stakes analysis
- Best-in-family consistency across repeated runs
Considerations & Trade-offs
- Slow and roughly ten times the price of o3
- Not designed for interactive, low-latency use
- GPT-5 Pro now offers better accuracy for less
Grok 4.20 (Reasoning) · Strengths & Key Advantages
- Expansive 1M-token context window tailored for dense repository and legal document intake
- Robust multi-step chain-of-thought reasoning with persistent long-horizon tool execution
- Multimodal ingestion across technical diagrams, multi-page PDFs, and complex charts
- Direct real-time knowledge synthesis from xAI Colossus cluster
Considerations & Trade-offs
- Outperformed by Grok 4.7 and late-2026 frontier leaders on competitive coding benchmarks
- Higher output latency during extended chain-of-thought generation cycles
Token Use & Task Economics
Estimated cost and token consumption to complete one representative agentic task.
| Metric | o3-pro | Grok 4.20 (Reasoning) |
|---|---|---|
Cost per Task Estimated USD to finish one task | $11.68 | $1.45 |
Output Tokens / Task Tokens generated per task | 58K | 45K |
Reasoning Tokens / Task Thinking tokens burned per task | 38K | 28K |
Technical Specifications
Architecture, release timeline, capabilities, and modalities.
| Feature | o3-pro | Grok 4.20 (Reasoning) |
|---|---|---|
| Official API Model ID (SDK) | o3-pro | grok-4-20-reasoning-latest |
| API Protocol | OpenAI Responses API & Chat Completions v1 | xAI REST API (OpenAI-Compatible) |
| Release Date | 2025-06 | 2026-03 |
| Knowledge Cutoff | June 2024 | November 2025 |
| Architecture | High-effort reasoning transformer | Colossus-Scale Reasoning Sparse MoE |
| Parameters | Confidential | Confidential |
| Enterprise Rate Limits (RPM / TPM) | 10,000 – 30,000 RPM (Tier 5 Enterprise) · 800,000 – 2,000,000 TPM | 5,000 – 15,000 RPM (Production Tier) · 4,000,000 – 10,000,000 TPM |
| Long-Context Tier (>128K/200K) | Flat rate ($20/1M in) across full 200K window | Flat rate ($3/1M in) across full 1000K window |
| Prompt Cache Policy & TTL | Automatic prefix caching at $5/1M (no extra cache-write fee) | Cached input at $0.75/1M tokens |
| Computer Use / GUI Agent | Supported (Screen coordinate grounding, browser & desktop GUI action loops) | API / CLI Tool-Use & DOM Agent ready (no raw pixel desktop click loop) |
| MCP & Parallel Tool Calling | Native MCP Client/Server ready · Parallel function calling · 100% Strict JSON Schema | Native MCP Client/Server ready · Parallel function calling · 100% Strict JSON Schema |
| Web Search Grounding & Sandbox | Native Web Search tool + Hosted Code Interpreter & File Search RAG | Real-time Web & X (Twitter) Search Grounding + Code Execution |
| Official Fine-Tuning Support | Supervised Fine-Tuning (SFT), Direct Preference (DPO) & Reinforcement Fine-Tuning (RFT) | API Prompt Engineering & RAG Distillation |
| Multimodal Token Billing | Text BPE (~4 chars/token) · Vision (~258–765 tokens per image tile) | Text BPE (~4 chars/token) · Vision (~258–765 tokens per image tile) |
| Quantization & Min GPU VRAM | Cloud-Hosted Proprietary (FP8 / BF16 Tensor Core Cluster) · Zero Local VRAM Required (100% Serverless Cloud API) | Cloud-Hosted Proprietary (FP8 / BF16 Tensor Core Cluster) · Zero Local VRAM Required (100% Serverless Cloud API) |
| Safety & Frontier Classification | OpenAI Preparedness Framework Audited & System Card Published | xAI Production Safety & Alignment Verified |
| Enterprise Compliance (ZDR/HIPAA/SOC2) | SOC2 Type II · GDPR · Zero Data Retention (ZDR) & HIPAA BAA Available on Enterprise Tier | SOC2 Type II · GDPR · Zero Data Retention (ZDR) & HIPAA BAA Available on Enterprise Tier |
| Input Modalities | text, vision | text, vision |
| Output Modalities | text | text |
o3-pro vs Grok 4.20 (Reasoning): Quick Answers
Which is more intelligent, o3-pro or Grok 4.20 (Reasoning)?
Grok 4.20 (Reasoning) is more intelligent. It scores 68 compared with 58 on the composite Intelligence Index.
Which model is faster?
Grok 4.20 (Reasoning) is faster, generating 95 tokens per second compared with 30 tokens per second.
Which model is cheaper to run?
Grok 4.20 (Reasoning) is cheaper at $2.63 per 1M tokens blended, compared with $15.50 (7:2:1 cache:input:output ratio).
Which model has lower latency?
Grok 4.20 (Reasoning) has lower latency, with a time to first token of 0.98s compared with 5.20s.
Which model has a larger context window?
Grok 4.20 (Reasoning) has a larger context window, supporting 1M tokens compared with 200K tokens.
Verdict
Verdict & Model Selection Recommendation: Choose o3-pro if your priority is Batch and mission-critical analysis rather than chat. Its performance in demanding tasks justifies its operational token cost. Choose Grok 4.20 (Reasoning) if your workflow prioritizes Deep document analysis, multi-stage enterprise research, and extensive tool-driven workflows. For large-scale batch processing or customer-facing conversational interfaces, its balance of speed and economics delivers superior ROI.
Frequently asked questions
How does o3-pro compare to Grok 4.20 (Reasoning) in API token pricing and cost per token?+
o3-pro costs $20.00 per 1M input tokens and $80.00 per 1M output tokens, whereas Grok 4.20 (Reasoning) costs $3.00 input and $15.00 output. Overall, Grok 4.20 (Reasoning) is the more cost-effective model for high-volume API pipelines. Both models support prompt caching discounts of up to 90% for repeated prompt prefixes.
Which model has a larger context window: o3-pro or Grok 4.20 (Reasoning)?+
o3-pro supports a context window of 200K tokens (~150k words), while Grok 4.20 (Reasoning) supports 1,000K tokens (~750k words). Therefore, Grok 4.20 (Reasoning) can process more textual data and document context in a single prompt.
Which AI model is better for software engineering and coding: o3-pro or Grok 4.20 (Reasoning)?+
o3-pro scores 71.5% on SWE-bench Verified while Grok 4.20 (Reasoning) scores 68.2%. For autonomous software engineering and multi-file debugging, o3-pro holds the verified benchmark lead.
What is the difference in reasoning capability and extended thinking between o3-pro and Grok 4.20 (Reasoning)?+
o3-pro features native chain-of-thought extended thinking mode with configurable reasoning effort. In contrast, Grok 4.20 (Reasoning) provides chain-of-thought reasoning depth for complex math and science.
How does inference speed (tokens per second) compare between o3-pro and Grok 4.20 (Reasoning)?+
o3-pro generates approximately 30 tokens per second, while Grok 4.20 (Reasoning) delivers 95 tokens per second. In latency-sensitive production environments, Grok 4.20 (Reasoning) provides faster time-to-first-token (TTFT) and higher streaming response velocity.
Can you implement a tiered LLM routing setup combining o3-pro and Grok 4.20 (Reasoning) to optimize costs?+
Yes! High-efficiency architectures route high-frequency routine classification and conversational tasks to Grok 4.20 (Reasoning) to save operational costs, and dynamically escalate complex architectural queries or reasoning tasks to o3-pro. This tiered routing pattern cuts overall API bills by up to 70%.
Understand key metrics like context window, token pricing, reasoning mode, and SWE-bench scores in our comprehensive AI glossary.
Related reading
- GPT-5 Chat vs o3-pro: Benchmarks, Pricing & Speed ComparisonCompare
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- Grok 4.20 (Reasoning) vs DeepSeek R1: Benchmarks, Pricing & Speed ComparisonCompare
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- Grok 4.20 (Reasoning) vs o3: Benchmarks, Pricing & Speed ComparisonCompare
- Grok Build 0.1 vs Grok 4.20 (Reasoning): Benchmarks, Pricing & Speed ComparisonCompare
Benchmark scores, token prices, and rate limits evolve rapidly as AI labs release model updates. Always verify current specifications and pricing on the official provider documentation.
Sources: GetInfoUs Independent AI Benchmarks & Official API Specs