Compare / head-to-head
GPT-5.5vsGrok 4.20 Reasoning
GPT-5.5 leads 4 of 5 shared benchmarks. Grok 4.20 Reasoning is 9.3x cheaper per token. Both offer a 1M-token context window.
Benchmarks from cited public sources; pricing from official pages; status from official provider feeds.
Shared benchmarks
4 – 1
GPT-5.5 leads
Cheaper per token
Grok 4.20 Reasoning
9.3x cheaper, input + output
Larger context
Tie
both 1M tokens
Provider uptime (30d)
95.4802% · —
OpenAI · xAI
GPT-5.5
OpenAI · released 2026-04-23
textvision
Grok 4.20 Reasoning
xAI · released 2026-03-09
textvision
Quality
Benchmark matrix
5 shared · 16 only GPT-5.5 · 0 only Grok 4.20 Reasoning| Benchmark | GPT-5.5 | Grok 4.20 Reasoning | Δ | Edge |
|---|---|---|---|---|
| Reported by both · 5 | ||||
| GPQA Diamond | 90.7% ↗epoch | 89.3% ↗epoch | +1.4 pt | GPT-5.5 |
| FrontierMath Tier 4 v2 (Epoch AI run) | 72.5% ↗epoch | 17.1% ↗epoch | +55.4 pt | GPT-5.5 |
| FrontierMath Tiers 1-3 v2 (Epoch AI run) | 85.3% ↗epoch | 44.9% ↗epoch | +40.4 pt | GPT-5.5 |
| OTIS Mock AIME 2024-2025 (Epoch AI run) | 84.4% ↗epoch | 92.2% ↗epoch | -7.8 pt | Grok 4.20 Reasoning |
| SimpleQA Verified | 63% ↗epoch | 30.2% ↗epoch | +32.8 pt | GPT-5.5 |
| Only GPT-5.5 reports · 16 | ||||
| AIME 2026 | 100% ↗matharena ⚠ | not reported | — | — |
| LMArena Elo | 1465.6 ↗ | not reported | — | — |
| ARC-AGI-1 (Verified) | 95% ↗ | not reported | — | — |
| ARC-AGI-2 (Verified) | 85% ↗ | not reported | — | — |
| BrowseComp | 84.4% ↗ | not reported | — | — |
| FrontierMath Tier 1-3 | 51.7% ↗ | not reported | — | — |
| FrontierMath Tier 4 | 35.4% ↗ | not reported | — | — |
| GDPval (wins or ties) | 84.9% ↗ | not reported | — | — |
| MCP Atlas | 75.3% ↗ | not reported | — | — |
| MMMU-Pro (no tools) | 81.2% ↗ | not reported | — | — |
| MMMU-Pro (with tools) | 83.2% ↗ | not reported | — | — |
| OSWorld-Verified | 78.7% ↗ | not reported | — | — |
| SWE-Bench Pro | 58.6% ↗ | not reported | — | — |
| Tau2-bench Telecom | 98% ↗ | not reported | — | — |
| Terminal-Bench 2.0 | 82.7% ↗ | not reported | — | — |
| Toolathlon | 55.6% ↗ | not reported | — | — |
| Only Grok 4.20 Reasoning reports · 0 | ||||
| Grok 4.20 Reasoning reports nothing GPT-5.5 does not. | ||||
Scores tagged "epoch" or "matharena" are independent runs, used only where the lab has not published its own; ⚠ marks rows MathArena flags as released after the competition. Higher is better on every row. Δ is GPT-5.5 minus Grok 4.20 Reasoning in the benchmark's own unit. "Not reported" means the lab has not published that figure; it is not a zero. ↗ opens the source.
Specs & pricing
Side by side
Official pricing pages and model cards| Spec | GPT-5.5 | Grok 4.20 Reasoning | Edge |
|---|---|---|---|
| Context window | 1M tokens | 1M tokens | Tie |
| Max output | 128K tokens | — | — |
| Input price / 1M | $5 ↗ | $1.25 ↗ | Grok 4.20 Reasoning |
| Output price / 1M | $30 ↗ | $2.5 ↗ | Grok 4.20 Reasoning |
| Cached input / 1M | $0.5 ↗ | $0.2 ↗ | Grok 4.20 Reasoning |
| Input + output / 1M Lower is cheaper. List prices; batch, tool and regional fees excluded. | $35 | $3.75 | Grok 4.20 Reasoning |
| Modalities | text · vision | text · vision | Tie |
| Released | 2026-04-23 | 2026-03-09 | — |
| Cited benchmark scores | 21 | 5 | — |
Reliability
Provider status
Last 60 days · refreshed daily on this page · live on /statusMore matchups
GPT-5.5 vs …
Models sharing the most benchmarksMore matchups
Grok 4.20 Reasoning vs …
Models sharing the most benchmarksBuilt by Respan
Which one wins on your data?
Public benchmarks are a starting point. Run GPT-5.5 and Grok 4.20 Reasoning on your own prompts with Respan evals, or route to either through one gateway key with automatic failover.