Data points: 138
Model compare
The readout for GPT-5.1 and GPT-5.5, before the detailed comparison sheet.
Weighted outcome: GPT-5.5. Benchmark capability categories carry 80%, while price, API performance, and availability carry 20%.
Decision read
GPT-5.5
GPT-5.5 has the higher weighted result; Model A / B score 16 to 84.
Evidence depth
138 data points
Includes 29 benchmark rows, 3 audit samples, and 6 provider examples.
Selection signal
Start with GPT-5.5
The charts below split 38 high-signal samples across speed, scores, and audit health.
Switch either side of this report to compare another model with the same LMSpeed data pipeline.
Select a different model to open a new comparison URL.
This report only uses LMSpeed data for GPT-5.1 and GPT-5.5: pricing, speed aggregates, third-party benchmark scores, and shared provider samples.
| Model compare | GPT-5.1 | GPT-5.5 |
|---|---|---|
| Overall leader | Contender | Leading |
| Weighted overall score | 16.0 pts | 84.0 pts |
| Benchmark category leads | 0 categories | 6 categories |
| Operational advantages | Cheapest input price, Average speed, First-token latency, Provider coverage | Free providers |
| Context window | 400K tokens | 1.1M tokens |
| Max output | 128K tokens | 128K tokens |
| Modalities | Input ImageTextFile Output Text |
The overall result weights benchmark capability categories at 80% and price, API speed/latency, and availability at 20%. Recent test volume does not affect the winner, and missing benchmark categories are excluded.
| Model compare | GPT-5.1 | GPT-5.5 |
|---|---|---|
| Developer | OpenAI | OpenAI |
| Released | Nov 2025 | Apr 2026 |
| Parameters | No data | No data |
| Tokenizer | GPT | GPT |
| Knowledge cutoff | No data | 2025-12-01 |
| OpenRouter ID | openai/gpt-5.1 | openai/gpt-5.5 |
| References | No data | No data |
This report only uses LMSpeed data for GPT-5.1 and GPT-5.5: pricing, speed aggregates, third-party benchmark scores, and shared provider samples.
GPT-5.1
GPT-5.1 has these operational advantages: Cheapest input price, Average speed, First-token latency, Provider coverage.
GPT-5.5
GPT-5.5 is stronger in benchmark categories (Agents, Coding, Reasoning, Knowledge, Math) and operational dimensions (Free providers).
Third-party benchmark profile synced into LMSpeed; only metrics available for both models are shown.
Compare benchmark category scores on a 0-100 scale. Select a category to inspect the gap.
Avg. score
GPT-5.1
52
Avg. score
GPT-5.5
58.7
GPT-5.5 leads by 14.9
GPT-5.5 leads by 10.9
GPT-5.5 leads by 6.9
GPT-5.5 leads by 6.1
GPT-5.5 leads by 2.9
No data
GPT-5.5
GPT-5.5 leads by 1.2
Metric-level scores with benchmark source, rank depth, confidence, error, and evaluation date where available.
GPT-5.1
56.0
Rank #47/90 · confidence 1 · eval date 2025-11-13
GPT-5.5
winner72.0
Rank #13/90 · confidence 3 · eval date 2026-04-23
GPT-5.1
winner$1.25/M
Rank #110/169 · confidence 4
GPT-5.5
$5.00/M
Rank #152/169 · confidence 4
GPT-5.1
winner$3.44/M
Rank #123/169 · confidence 4
GPT-5.5
$11.25/M
Rank #158/169 · confidence 4
GPT-5.1
winner$10.00/M
Rank #126/169 · confidence 4
GPT-5.5
$30.00/M
Rank #158/169 · confidence 4
GPT-5.1
winner75.0
Rank #3/94 · confidence 1 · eval date 2025-11-13
GPT-5.5
74.3
Rank #5/94 · confidence 3 · eval date 2026-04-23
GPT-5.1
87.3%
Rank #36/194 · confidence 4
GPT-5.5
winner93.5%
Rank #3/194 · confidence 4
GPT-5.1
4.9
Rank #38/77 · confidence 1 · eval date 2025-11-13
GPT-5.5
winner27.1
Rank #7/77 · confidence 3 · eval date 2026-04-23
GPT-5.1
26.5%
Rank #45/193 · confidence 4
GPT-5.5
winner44.3%
Rank #9/193 · confidence 4
GPT-5.1
24.6
Rank #18/33 · confidence 1 · eval date 2025-11-13
GPT-5.5
winner69.8
Rank #2/33 · confidence 3 · eval date 2026-04-23
GPT-5.1
49.4
Rank #36/64 · confidence 1 · eval date 2025-11-13
GPT-5.5
winner74.9
Rank #6/64 · confidence 3 · eval date 2026-04-23
GPT-5.1
43.3
Rank #49/101 · confidence 1 · eval date 2025-11-13
GPT-5.5
winner56.1
Rank #6/101 · confidence 3 · eval date 2026-04-23
GPT-5.1
43.3%
Rank #46/191 · confidence 4
GPT-5.5
winner56.1%
Rank #6/191 · confidence 4
GPT-5.1
31.0
Rank #19/47 · confidence 1 · eval date 2025-11-13
GPT-5.5
winner51.7
Rank #4/47 · confidence 3 · eval date 2026-04-23
GPT-5.1
12.5
Rank #16/35 · confidence 1 · eval date 2025-11-13
GPT-5.5
winner35.4
Rank #6/35 · confidence 3 · eval date 2026-04-23
GPT-5.1
49.9
Rank #31/57 · confidence 1 · eval date 2025-11-13
GPT-5.5
winner71.3
Rank #15/57 · confidence 3 · eval date 2026-04-23
GPT-5.1
87.3
Rank #39/101 · confidence 1 · eval date 2025-11-13
GPT-5.5
winner93.5
Rank #3/101 · confidence 3 · eval date 2026-04-23
GPT-5.1
37.6
Rank #35/95 · confidence 1 · eval date 2025-11-13
GPT-5.5
winner56.9
Rank #3/95 · confidence 3 · eval date 2026-04-23
GPT-5.1
26.5
Rank #43/101 · confidence 1 · eval date 2025-11-13
GPT-5.5
winner44.3
Rank #7/101 · confidence 3 · eval date 2026-04-23
GPT-5.1
36.9
Rank #46/104 · confidence 1 · eval date 2025-11-13
GPT-5.5
winner54.8
Rank #7/104 · confidence 3 · eval date 2026-04-23
GPT-5.1
5.6
Rank #23/34 · confidence 1 · eval date 2025-11-13
GPT-5.5
winner20.1
Rank #10/34 · confidence 3 · eval date 2026-04-23
GPT-5.1
51.3
Rank #67/95 · confidence 1 · eval date 2025-11-13
GPT-5.5
winner85.5
Rank #24/95 · confidence 3 · eval date 2026-04-23
GPT-5.1
75.5
Rank #26/61 · confidence 1 · eval date 2025-11-13
GPT-5.5
winner79.9
Rank #11/61 · confidence 3 · eval date 2026-04-23
GPT-5.1
1212.0
Rank #41/69 · confidence 1 · eval date 2025-11-13
GPT-5.5
winner1280.0
Rank #23/69 · confidence 3 · eval date 2026-04-23
GPT-5.1
72.9
Rank #30/86 · confidence 1 · eval date 2025-11-13
GPT-5.5
winner75.9
Rank #16/86 · confidence 3 · eval date 2026-04-23
GPT-5.1
41.2
Rank #35/50 · confidence 1 · eval date 2025-11-13
GPT-5.5
winner72.9
Rank #2/50 · confidence 3 · eval date 2026-04-23
GPT-5.1
81.9
Rank #54/84 · confidence 1 · eval date 2025-11-13
GPT-5.5
winner98.0
Rank #8/84 · confidence 3 · eval date 2026-04-23
GPT-5.1
21.0
Rank #41/60 · confidence 1 · eval date 2025-11-13
GPT-5.5
winner44.9
Rank #10/60 · confidence 3 · eval date 2026-04-23
GPT-5.1
24.4
Rank #40/55 · confidence 1 · eval date 2025-11-13
GPT-5.5
winner49.6
Rank #12/55 · confidence 3 · eval date 2026-04-23
GPT-5.1
988.0
Rank #40/60 · confidence 1 · eval date 2025-11-13
GPT-5.5
winner1491.0
Rank #12/60 · confidence 3 · eval date 2026-04-23
Latest completed audits from shared providers, with four safety and integrity score groups plus report links.
| Provider | GPT-5.1 | GPT-5.5 |
|---|---|---|
Winner: GPT-5.5 | GPT-5.1 gpt-5.1-2025-11-13 No audit yet | GPT-5.5 gpt-5.5 Audit score 100 100100100100 |
Winner: GPT-5.5 | GPT-5.1 gpt-5.1 No audit yet | GPT-5.5 gpt-5.5 Audit score 96 10084100100 |
Winner: GPT-5.5 | GPT-5.1 gpt-5.1 No audit yet | GPT-5.5 gpt-5.5 Audit score 88 8468100100 |
Speed aggregates and input/output pricing share each provider row for real API selection and migration cost checks.
| Provider | GPT-5.1 | GPT-5.5 |
|---|---|---|
35 tests | GPT-5.1 speed / latency N/A / N/A input / output No data | GPT-5.5 speed / latency 38 tok/s / 8937ms input / output No data |
10 tests | GPT-5.1 speed / latency 137 tok/s / 3299ms input / output No data | GPT-5.5 speed / latency N/A / N/A input / output No data |
10 tests | GPT-5.1 speed / latency N/A / N/A input / output No data | GPT-5.5 speed / latency 43 tok/s / 2874ms input / output No data |
5 tests | GPT-5.1 speed / latency N/A / N/A input / output No data | GPT-5.5 speed / latency 58 tok/s / 3313ms input / output No data |
5 tests | GPT-5.1 speed / latency 96 tok/s / 1862ms input / output No data | GPT-5.5 speed / latency N/A / N/A input / output No data |
GPT-5.1 gpt-5.1-chat-latest speed / latency No data input / output $0/request | GPT-5.5 gpt-5.5 speed / latency No data input / output $0/request |
Weighted outcome: GPT-5.5. Benchmark capability categories carry 80%, while price, API performance, and availability carry 20%.
Input
Output
| Features | Text inputImage inputFile inputText outputTool callingStructured outputsJSON modeReasoning | Text inputImage inputFile inputText outputTool callingStructured outputsJSON modeReasoning |
|---|
