Model comparison
Gemini 3.5 Flash Lite vs GPT-5.1-Codex
Gemini 3.5 Flash Lite is the stronger model overall, scoring 41.5 to 38.6 on the Noometry Index.
Last verified . 3 shared benchmarks.
GoogleSummary
- They share 3 benchmarks with published results for both. Gemini 3.5 Flash Lite scores higher in 1 category and GPT-5.1-Codex in 2 categories; 2 gaps are clear of the uncertainty.
- The widest gap is in agentic & tool use, where GPT-5.1-Codex leads 38.0 to 25.7.
- Gemini 3.5 Flash Lite is cheaper at $0.30 / $2.50 per million input/output tokens, against $1.25 / $10 for GPT-5.1-Codex.
- Gemini 3.5 Flash Lite accepts more context: 1.05M tokens versus 400K.
Side by side
| Gemini 3.5 Flash Lite | GPT-5.1-Codex | |
|---|---|---|
| Provider | OpenAI | |
| Noometry Index | 41.5 | 38.6 |
| Released | 2026-07-21 | 2025-11-12 |
| Weights | Proprietary | Proprietary |
| Context window | 1.05M | 400K |
| Max output | 66K | 128K |
| Input $ / M tokens | $0.30 | $1.25 |
| Output $ / M tokens | $2.50 | $10 |
| Results tracked | 39 | 6 |
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Category by category
Coding Too close to call
Gemini 3.5 Flash Lite: 42.4 (#104), GPT-5.1-Codex: 41.9 (#116)
| Benchmark | Gemini 3.5 Flash Lite | GPT-5.1-Codex |
|---|---|---|
| LMArena WebDev | 1440 | 1337 |
| ALE-Bench | 765.27 | 1,245 |
| SWE-bench Verified (bash only) | — | 66% |
| SciCode | 41.3% | — |
| WeirdML | 39% | — |
| LMArena Coding | 1453 | — |
Agentic & Tool Use GPT-5.1-Codex leads
Gemini 3.5 Flash Lite: 25.7 (#107), GPT-5.1-Codex: 38.0 (#33)
| Benchmark | Gemini 3.5 Flash Lite | GPT-5.1-Codex |
|---|---|---|
| Terminal-Bench | — | 60.4% |
| APEX-Agents | 29.3% | — |
| GDP.pdf | 10% | — |
| METR Time Horizons | — | 70.8% |
Reasoning Not comparable
Gemini 3.5 Flash Lite: 27.8 (#114), GPT-5.1-Codex: —
| Benchmark | Gemini 3.5 Flash Lite | GPT-5.1-Codex |
|---|---|---|
| ARC-AGI-2 | 10.3% | — |
| NYT Connections (extended) | 60.4% | — |
| ARC-AGI-1 | 53.5% | — |
| CritPt | 0% | — |
| Chess Puzzles | 22% | — |
| LMArena Hard Prompts | 1441 | — |
| Mystery Game Puzzles | 19% | — |
| DTBench | 83.5% | — |
| LMCA | 37.6% | — |
| Epoch Capabilities Index | 145.13 | — |
Math GPT-5.1-Codex leads
Gemini 3.5 Flash Lite: 25.9 (#264), GPT-5.1-Codex: 30.3 (#235)
| Benchmark | Gemini 3.5 Flash Lite | GPT-5.1-Codex |
|---|---|---|
| ProofBench | 13% | 9% |
| FrontierMath (Tiers 1-3) | 26% | — |
| FrontierMath Tier 4 | 0% | — |
| OTIS Mock AIME 2024-2025 | 71.1% | — |
| LMArena Math | 1433 | — |
Knowledge Not comparable
Gemini 3.5 Flash Lite: 50.1 (#72), GPT-5.1-Codex: —
| Benchmark | Gemini 3.5 Flash Lite | GPT-5.1-Codex |
|---|---|---|
| GPQA Diamond | 83.3% | — |
| LMArena Expert | 1435 | — |
Multimodal Not comparable
Gemini 3.5 Flash Lite: 41.1 (#40), GPT-5.1-Codex: —
| Benchmark | Gemini 3.5 Flash Lite | GPT-5.1-Codex |
|---|---|---|
| LMArena Vision | 1268 | — |
Multilingual Not comparable
Gemini 3.5 Flash Lite: 53.5 (#63), GPT-5.1-Codex: —
| Benchmark | Gemini 3.5 Flash Lite | GPT-5.1-Codex |
|---|---|---|
| LMArena Non-English | 1427 | — |
| LMArena Chinese | 1469 | — |
| LMArena French | 1451 | — |
| LMArena German | 1454 | — |
| LMArena Japanese | 1427 | — |
| LMArena Korean | 1407 | — |
| LMArena Russian | 1443 | — |
| LMArena Spanish | 1442 | — |
Instruction Following Not comparable
Gemini 3.5 Flash Lite: 74.8 (#85), GPT-5.1-Codex: —
| Benchmark | Gemini 3.5 Flash Lite | GPT-5.1-Codex |
|---|---|---|
| LMArena Instruction Following | 1420 | — |
Long Context Not comparable
Gemini 3.5 Flash Lite: 43.9 (#84), GPT-5.1-Codex: —
| Benchmark | Gemini 3.5 Flash Lite | GPT-5.1-Codex |
|---|---|---|
| LMArena Longer Query | 1435 | — |
Writing & Preference Not comparable
Gemini 3.5 Flash Lite: 64.2 (#57), GPT-5.1-Codex: —
| Benchmark | Gemini 3.5 Flash Lite | GPT-5.1-Codex |
|---|---|---|
| LMArena Text | 1435 | — |
| LMArena Creative Writing | 1420 | — |
| EQ-Bench Creative Writing | 1559 | — |
| LMArena Multi-Turn | 1445 | — |
Frequently asked questions
Is Gemini 3.5 Flash Lite better than GPT-5.1-Codex?
Gemini 3.5 Flash Lite is the stronger model overall, scoring 41.5 to 38.6 on the Noometry Index.
Which is cheaper, Gemini 3.5 Flash Lite or GPT-5.1-Codex?
Gemini 3.5 Flash Lite is cheaper. It lists at $0.30 per million input tokens and $2.50 per million output tokens; GPT-5.1-Codex lists at $1.25 and $10.
Is Gemini 3.5 Flash Lite or GPT-5.1-Codex better for coding?
They score almost the same on coding (42.4 vs 41.9); test both on your own repository before choosing.
Which has the bigger context window?
Gemini 3.5 Flash Lite does, with 1.05M tokens against 400K.
How many benchmarks do Gemini 3.5 Flash Lite and GPT-5.1-Codex share?
3 benchmarks have published results for both models. Gemini 3.5 Flash Lite has 39 scored results on Noometry and GPT-5.1-Codex has 6.