Model comparison
Grok 4 Fast (Reasoning) vs o3
Head-to-head evidence from 12 shared benchmark results across 6 categories. Overall scores shown here use the public BenchAlign v5 ranking lane.
Public leaderboard positions: Grok 4 Fast (Reasoning) #76 (Supported); o3 #131 (Supported). Intervals and evidence labels describe ranking uncertainty, not a guarantee for a specific workload.
Evidence parity. Grok 4 Fast (Reasoning) and o3 share 12 comparable benchmark results. 0 of 8 categories are comparable. 1 result is unique to Grok 4 Fast (Reasoning); 4 to o3.
Updated July 23, 2026- Shared results
- 12
- Grok 4 Fast (Reasoning) only
- 1
- o3 only
- 4
- Comparable categories
- 0 / 8
Benchmark data for Grok 4 Fast (Reasoning) and o3 is coming soon on BenchLM.
Confidence note. This is a partial-evidence comparison with 12 shared benchmark results across 6 evidence categories; 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.
Grok 4 Fast (Reasoning) has the larger context window at 2M, compared with 200K for o3.
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 Fast (Reasoning) | Δ | o3 |
|---|---|---|---|
| Math | Grok 4 Fast (Reasoning)Not measured | MarginNo overlap | o314.5 |
Operational comparison
Runtime and commercial metrics are compared only when both models have a complete sourced value.
| Metric | Grok 4 Fast (Reasoning) | o3 | Comparison |
|---|---|---|---|
| Input / output priceUSD per 1M tokens | Grok 4 Fast (Reasoning)Not available | o3$2 input / $8 output | A complete price comparison is not available. |
| Generation speedtokens per second | Grok 4 Fast (Reasoning)Not available | o3118 tok/s | A complete speed comparison is not available. |
| First-answer latencyseconds to first token | Grok 4 Fast (Reasoning)Not available | o35.38 s | A complete latency comparison is not available. |
| Context windowmaximum listed tokens | Grok 4 Fast (Reasoning)2M | o3200K | Grok 4 Fast (Reasoning) lists the larger context window. |
Benchmark Deep Dive
Agentic1 benchmarks
| Benchmark | Grok 4 Fast (Reasoning) | o3 | Result |
|---|---|---|---|
| τ²-bench resultsSource | 65.8% | 80.7% | o3 leads |
Coding2 benchmarks
Reasoning2 benchmarks
Knowledge6 benchmarks
| Benchmark | Grok 4 Fast (Reasoning) | o3 | Result |
|---|---|---|---|
| Artificial Analysis Intelligence IndexSource | 27.4% | 30.4% | o3 leads |
| AA-GPQA DiamondSource | 84.7% | 82.7% | Grok 4 Fast (Reasoning) leads |
| AA-HLESource | 17.0% | 20.0% | o3 leads |
| AA-Omniscience IndexSource | -28.4% | -15.3% | o3 leads |
| AA-Omniscience AccuracySource | 22.6% | 38.4% | o3 leads |
| AA-Omniscience Hallucination RateSource | 66.0% | 87.1% | Grok 4 Fast (Reasoning) leads |
Math3 benchmarks
Multimodal2 benchmarks
Inst. Following1 benchmarks
| Benchmark | Grok 4 Fast (Reasoning) | o3 | Result |
|---|---|---|---|
| AA-IFBenchSource | 50.5% | 71.4% | o3 leads |
Frequently Asked Questions (3)
Can I compare Grok 4 Fast (Reasoning) and o3 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 Fast (Reasoning) and o3 today?
o3: $2.00 input / $8.00 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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