Model comparison
GPT-5.1 vs GPT-5.5
Head-to-head evidence from 21 shared benchmark results across 7 categories. Overall scores shown here use the public BenchAlign v5 ranking lane.
Public leaderboard positions: GPT-5.1 #94 (Estimated); GPT-5.5 #9 (Estimated). Intervals and evidence labels describe ranking uncertainty, not a guarantee for a specific workload.
Evidence parity. GPT-5.1 and GPT-5.5 share 21 comparable benchmark results. 1 of 8 categories are comparable. 0 results are unique to GPT-5.1; 36 to GPT-5.5.
Updated July 22, 2026- Shared results
- 21
- GPT-5.1 only
- 0
- GPT-5.5 only
- 36
- Comparable categories
- 1 / 8
Pick GPT-5.5 if you want the stronger benchmark profile. GPT-5.1 only becomes the better choice if you want the cheaper token bill.
Confidence note. This is a partial-evidence comparison with 21 shared benchmark results across 7 evidence categories; 1 of 8 categories currently have scoreable aggregates for both models. Treat the verdict as directional until coverage is more balanced.
Why this result
GPT-5.5 is clearly ahead on the BenchAlign aggregate, 73.51 to 53.65. The gap is large enough that you do not need to squint at the spreadsheet to see the difference.
GPT-5.5's sharpest advantage is in mathematics, where it averages 47.6 against 26.4. The single biggest benchmark swing on the page is FrontierMath v2 (Tier 4), 12.500% to 35.400%.
GPT-5.5 is also the more expensive model on tokens at $5.00 input / $30.00 output per 1M tokens, versus $1.25 input / $10.00 output per 1M tokens for GPT-5.1. That is roughly 3.0x on output cost alone. GPT-5.5 gives you the larger context window at 1M, compared with 200K for GPT-5.1.
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 | GPT-5.1 | Δ | GPT-5.5 |
|---|---|---|---|
| Math | GPT-5.126.4 | Margin→ 21.2 | GPT-5.547.6 |
| Agentic | GPT-5.1Not measured | MarginNo overlap | GPT-5.581.6 |
| Coding | GPT-5.1Not measured | MarginNo overlap | GPT-5.558.6 |
| Reasoning | GPT-5.1Not measured | MarginNo overlap | GPT-5.585.0 |
| Knowledge | GPT-5.1Not measured | MarginNo overlap | GPT-5.557.8 |
| Multimodal | GPT-5.1Not measured | MarginNo overlap | GPT-5.570.4 |
Decisive benchmark drivers
The largest measured benchmark gaps in this matchup, with exact reported values.
More
- Source ↗
FrontierMath v2 (Tier 4)
MathA 12.500%B 35.400%Winner: GPT-5.5Δ 22.9FrontierMath v2 (Tier 4): GPT-5.1 scored 12.500%; GPT-5.5 scored 35.400%. GPT-5.5 wins this benchmark. - Source ↗
FrontierMath v2 (Tiers 1-3)
MathA 31.034%B 51.700%Winner: GPT-5.5Δ 20.7FrontierMath v2 (Tiers 1-3): GPT-5.1 scored 31.034%; GPT-5.5 scored 51.700%. GPT-5.5 wins this benchmark.
Operational comparison
Runtime and commercial metrics are compared only when both models have a complete sourced value.
| Metric | GPT-5.1 | GPT-5.5 | Comparison |
|---|---|---|---|
| Input / output priceUSD per 1M tokens | GPT-5.1$1.25 input / $10 output | GPT-5.5$5 input / $30 output | GPT-5.1 has the lower combined listed price. |
| Generation speedtokens per second | GPT-5.1111 tok/s | GPT-5.5Not available | A complete speed comparison is not available. |
| First-answer latencyseconds to first token | GPT-5.157.47 s | GPT-5.5Not available | A complete latency comparison is not available. |
| Context windowmaximum listed tokens | GPT-5.1200K | GPT-5.51M | GPT-5.5 lists the larger context window. |
Benchmark Deep Dive
Agentic24 benchmarks
| Benchmark | GPT-5.1 | GPT-5.5 | Result |
|---|---|---|---|
| AA Agentic IndexSource | 21.0% | 44.9% | GPT-5.5 leads |
| τ²-bench resultsSource | 81.9% | 93.9% | GPT-5.5 leads |
| Gert LabsSource | 41.24% | 72.93% | GPT-5.5 leads |
| GDPval-AASource | 24.4% | 49.5% | GPT-5.5 leads |
| GDPval-AASource | 987 | 1490 | GPT-5.5 leads |
| Terminal-Bench 2.0Source | — | 82% | Not comparable |
| CyberGymSource | — | 81.8% | Not comparable |
| BrowseCompSource | — | 84.4% | Not comparable |
| OSWorld-VerifiedSource | — | 78.7% | Not comparable |
| MCP AtlasSource | — | 75.3% | Not comparable |
| ToolathlonSource | — | 55.6% | Not comparable |
| APEX-Agents-AASource | — | 37.7% | Not comparable |
| ResearchClawBenchSource | — | 17.0% | Not comparable |
| OSWorld 2.0Source | — | 13.0% | Not comparable |
| JobBenchSource | — | 42.7% | Not comparable |
| ExploitGymSource | — | 13.4% | Not comparable |
| AA BriefcaseSource | — | 1154 | Not comparable |
| AA AutomationBenchSource | — | 42.1% | Not comparable |
| AA EnterpriseOps-GymSource | — | 46.6% | Not comparable |
| AA Harvey LABSource | — | 86.3% | Not comparable |
| AA ITBenchSource | — | 45.8% | Not comparable |
| AA Tau3 BankingSource | — | 31.3% | Not comparable |
| terminalBenchHardSource | — | 60.6% | Not comparable |
| aaTerminalBench21Source | — | 84.3% | Not comparable |
Coding9 benchmarks
| Benchmark | GPT-5.1 | GPT-5.5 | Result |
|---|---|---|---|
| Vibe Code BenchSource | 24.61% | 69.85% | GPT-5.5 leads |
| AA Coding IndexSource | 49.4% | 74.9% | GPT-5.5 leads |
| AA-SciCodeSource | 43.3% | 56.1% | GPT-5.5 leads |
| SWE-bench ProSource | — | 58.6% | Not comparable |
| Terminal-Bench 2.0Source | — | 82.0% | Not comparable |
| React Native EvalsSource | — | 84.7% | Not comparable |
| cursorBench31Source | — | 59.2% | Not comparable |
| cursorBench32Source | — | 58.4% | Not comparable |
| FrontierCode 1.1 MainSource | — | 43.0% | Not comparable |
Reasoning5 benchmarks
Knowledge10 benchmarks
| Benchmark | GPT-5.1 | GPT-5.5 | Result |
|---|---|---|---|
| Artificial Analysis Intelligence IndexSource | 36.9% | 54.8% | GPT-5.5 leads |
| AA-GPQA DiamondSource | 87.3% | 93.5% | GPT-5.5 leads |
| AA-HLESource | 26.5% | 44.3% | GPT-5.5 leads |
| AA-Omniscience IndexSource | 5.6% | 20.1% | GPT-5.5 leads |
| AA-Omniscience AccuracySource | 37.6% | 56.9% | GPT-5.5 leads |
| AA-Omniscience Hallucination RateSource | 51.3% | 85.5% | GPT-5.1 leads |
| GPQASource | — | 93.6% | Not comparable |
| GPQA-DSource | — | 93.6% | Not comparable |
| HLESource | — | 52.2% | Not comparable |
| HLE w/o toolsSource | — | 41.4% | Not comparable |
MathGPT-5.5 wins3 benchmarks
Multimodal5 benchmarks
Inst. Following1 benchmarks
| Benchmark | GPT-5.1 | GPT-5.5 | Result |
|---|---|---|---|
| AA-IFBenchSource | 72.9% | 75.9% | GPT-5.5 leads |
Frequently Asked Questions (2)
Which is better, GPT-5.1 or GPT-5.5?
GPT-5.5 is ahead on BenchLM's BenchAlign leaderboard, 73.51 to 53.65. The biggest single separator in this matchup is FrontierMath v2 (Tier 4), where the scores are 12.500% and 35.400%.
Which is better for math, GPT-5.1 or GPT-5.5?
GPT-5.5 has the edge for math in this comparison, averaging 47.6 versus 26.4. Inside this category, FrontierMath v2 (Tier 4) is the benchmark that creates the most daylight between them.
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