Model comparison
Devstral Small 2505 vs GPT-5.5 Pro
GPT-5.5 Pro is the stronger model overall, scoring 64.3 to 33.9 on the Noometry Index. Devstral Small 2505 costs 450× less per token, which makes it the better buy when GPT-5.5 Pro's lead doesn't matter for your workload.
Last verified . 1 shared benchmarks.
Mistral AISummary
- They share 1 benchmark with published results for both. Devstral Small 2505 scores higher in 0 categories and GPT-5.5 Pro in 1 category; one gap is clear of the uncertainty.
- The widest gap is in reasoning, where GPT-5.5 Pro leads 73.6 to 19.1.
- The biggest single-benchmark swing is CritPt: 0% for Devstral Small 2505 and 30.6% for GPT-5.5 Pro.
- Devstral Small 2505 is cheaper at $0.10 / $0.30 per million input/output tokens, against $30 / $180 for GPT-5.5 Pro.
- GPT-5.5 Pro accepts more context: 1.05M tokens versus 128K.
- Devstral Small 2505 has downloadable open weights; the other is API-only.
Side by side
| Devstral Small 2505 | GPT-5.5 Pro | |
|---|---|---|
| Provider | Mistral AI | OpenAI |
| Noometry Index | 33.9 | 64.3 |
| Released | 2025-05-07 | 2026-04-23 |
| Weights | Open | Proprietary |
| Context window | 128K | 1.05M |
| Max output | 128K | 128K |
| Input $ / M tokens | $0.10 | $30 |
| Output $ / M tokens | $0.30 | $180 |
| Results tracked | 4 | 14 |
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Category by category
Coding Not comparable
Devstral Small 2505: 38.6 (#160), GPT-5.5 Pro: —
| Benchmark | Devstral Small 2505 | GPT-5.5 Pro |
|---|---|---|
| SWE-bench Verified (bash only) | 56.4% | — |
| SciCode | 28.8% | — |
Reasoning GPT-5.5 Pro leads
Devstral Small 2505: 19.1 (#243), GPT-5.5 Pro: 73.6 (#7)
| Benchmark | Devstral Small 2505 | GPT-5.5 Pro |
|---|---|---|
| CritPt | 0% | 30.6% |
| ARC-AGI-2 | — | 84.6% |
| SimpleBench | — | 76.9% |
| Kagi LLM Benchmark | 37.7% | — |
| ARC-AGI-1 | — | 96.5% |
| Chess Puzzles | — | 64% |
| DTBench | — | 96% |
| LMCA | — | 53.9% |
| Epoch Capabilities Index | — | 162.45 |
Math Not comparable
Devstral Small 2505: —, GPT-5.5 Pro: 83.8 (#8)
| Benchmark | Devstral Small 2505 | GPT-5.5 Pro |
|---|---|---|
| FrontierMath (Tiers 1-3) | — | 87.7% |
| FrontierMath Tier 4 | — | 78% |
| OTIS Mock AIME 2024-2025 | — | 100% |
| FrontierMath (Feb 2025 set) | — | 52.4% |
| FrontierMath Tier 4 (v1) | — | 39.6% |
Knowledge Not comparable
Devstral Small 2505: —, GPT-5.5 Pro: 64.2 (#17)
| Benchmark | Devstral Small 2505 | GPT-5.5 Pro |
|---|---|---|
| GPQA Diamond | — | 93.9% |
Frequently asked questions
Is Devstral Small 2505 better than GPT-5.5 Pro?
GPT-5.5 Pro is the stronger model overall, scoring 64.3 to 33.9 on the Noometry Index. Devstral Small 2505 costs 450× less per token, which makes it the better buy when GPT-5.5 Pro's lead doesn't matter for your workload.
Which is cheaper, Devstral Small 2505 or GPT-5.5 Pro?
Devstral Small 2505 is cheaper. It lists at $0.10 per million input tokens and $0.30 per million output tokens; GPT-5.5 Pro lists at $30 and $180.
Which has the bigger context window?
GPT-5.5 Pro does, with 1.05M tokens against 128K.
How many benchmarks do Devstral Small 2505 and GPT-5.5 Pro share?
1 benchmark has published results for both models. Devstral Small 2505 has 4 scored results on Noometry and GPT-5.5 Pro has 14.