Model comparison
Grok 4.20 vs Grok 4 Fast (Reasoning)
Head-to-head evidence from 1 shared benchmark result across 1 category. Overall scores shown here use the public BenchAlign v5 ranking lane.
Public leaderboard positions: Grok 4.20 #88 (Estimated); Grok 4 Fast (Reasoning) #76 (Supported). Intervals and evidence labels describe ranking uncertainty, not a guarantee for a specific workload.
Evidence parity. Grok 4.20 and Grok 4 Fast (Reasoning) share 1 comparable benchmark result. 0 of 8 categories are comparable. 17 results are unique to Grok 4.20; 12 to Grok 4 Fast (Reasoning).
Updated July 23, 2026- Shared results
- 1
- Grok 4.20 only
- 17
- Grok 4 Fast (Reasoning) only
- 12
- Comparable categories
- 0 / 8
Benchmark data for Grok 4.20 and Grok 4 Fast (Reasoning) is coming soon on BenchLM.
Confidence note. This is a partial-evidence comparison with 1 shared benchmark result across 1 evidence category; 0 of 8 categories currently have scoreable aggregates for both models. Treat the verdict as directional until coverage is more balanced.
Why this result
BenchLM has partial data for these models, but not enough overlapping benchmark coverage to produce a fair score-level comparison yet.
Category breakdown
Exact category averages are shown below. Not measured means BenchLM does not have enough sourced public coverage for that model and category.
| Category | Grok 4.20 | Δ | Grok 4 Fast (Reasoning) |
|---|---|---|---|
| Agentic | Grok 4.2047.1 | MarginNo overlap | Grok 4 Fast (Reasoning)Not measured |
| Coding | Grok 4.2067.1 | MarginNo overlap | Grok 4 Fast (Reasoning)Not measured |
| Reasoning | Grok 4.2053.3 | MarginNo overlap | Grok 4 Fast (Reasoning)Not measured |
| Multimodal | Grok 4.2070.1 | MarginNo overlap | Grok 4 Fast (Reasoning)Not measured |
Operational comparison
Runtime and commercial metrics are compared only when both models have a complete sourced value.
| Metric | Grok 4.20 | Grok 4 Fast (Reasoning) | Comparison |
|---|---|---|---|
| Input / output priceUSD per 1M tokens | Grok 4.20$2 input / $6 output | Grok 4 Fast (Reasoning)Not available | A complete price comparison is not available. |
| Generation speedtokens per second | Grok 4.20233 tok/s | Grok 4 Fast (Reasoning)Not available | A complete speed comparison is not available. |
| First-answer latencyseconds to first token | Grok 4.2010.33 s | Grok 4 Fast (Reasoning)Not available | A complete latency comparison is not available. |
| Context windowmaximum listed tokens | Grok 4.202M | Grok 4 Fast (Reasoning)2M | Listed context windows are equal. |
Benchmark Deep Dive
Agentic4 benchmarks
Coding5 benchmarks
Reasoning3 benchmarks
Knowledge10 benchmarks
| Benchmark | Grok 4.20 | Grok 4 Fast (Reasoning) | Result |
|---|---|---|---|
| GPQA-DSource | 88.5% | — | Not comparable |
| HLE w/o toolsSource | 31.6% | — | Not comparable |
| HealthBench HardSource | 20.3% | — | Not comparable |
| MedXpertQA (Text)Source | 50.2% | — | Not comparable |
| Artificial Analysis Intelligence IndexSource | — | 27.4% | Not comparable |
| AA-GPQA DiamondSource | — | 84.7% | Not comparable |
| AA-HLESource | — | 17.0% | Not comparable |
| AA-Omniscience IndexSource | — | -28.4% | Not comparable |
| AA-Omniscience AccuracySource | — | 22.6% | Not comparable |
| AA-Omniscience Hallucination RateSource | — | 66.0% | Not comparable |
Multimodal7 benchmarks
| Benchmark | Grok 4.20 | Grok 4 Fast (Reasoning) | Result |
|---|---|---|---|
| MMMU-ProSource | 75.2% | — | Not comparable |
| CharXivSource | 60.9% | — | Not comparable |
| ERQASource | 54.1% | — | Not comparable |
| SimpleVQASource | 57.4% | — | Not comparable |
| MedXpertQA (MM)Source | 65.8% | — | Not comparable |
| Design Arena WebsiteSource | 1257 | — | Not comparable |
| AA-MMMU-ProSource | — | 61.8% | Not comparable |
Inst. Following1 benchmarks
| Benchmark | Grok 4.20 | Grok 4 Fast (Reasoning) | Result |
|---|---|---|---|
| AA-IFBenchSource | — | 50.5% | Not comparable |
Frequently Asked Questions (3)
Can I compare Grok 4.20 and Grok 4 Fast (Reasoning) on BenchLM yet?
Not fully yet. BenchLM is tracking both models, but the sourced benchmark breakdown for this comparison is still coming soon.
Why does this comparison show “coming soon”?
BenchLM only shows category winners and benchmark-level calls when we have sourced results that can be compared fairly. For these models, the public benchmark coverage is not complete enough yet.
What data is available for Grok 4.20 and Grok 4 Fast (Reasoning) today?
Grok 4.20: $2.00 input / $6.00 output per 1M tokens Both model pages still include creator, context window, reasoning mode, and other metadata while benchmark coverage fills in.
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