Model comparison
GPT-5.5 Instant vs Kimi K2 (Jul 2025)
GPT-5.5 Instant is the stronger model overall, scoring 42.5 to 40.9 on the Noometry Index.
Last verified . 18 shared benchmarks.
Summary
- They share 18 benchmarks with published results for both. GPT-5.5 Instant scores higher in 6 categories and Kimi K2 (Jul 2025) in 2 categories; 6 gaps are clear of the uncertainty.
- The widest gap is in math, where Kimi K2 (Jul 2025) leads 40.1 to 26.1.
- Kimi K2 (Jul 2025) has downloadable open weights; the other is API-only.
Side by side
| GPT-5.5 Instant | Kimi K2 (Jul 2025) | |
|---|---|---|
| Provider | OpenAI | Moonshot AI |
| Noometry Index | 42.5 | 40.9 |
| Released | 2026-05-05 | 2025-07-12 |
| Weights | Proprietary | Open |
| Context window | — | 262K |
| Max output | — | 262K |
| Input $ / M tokens | — | $0.57 |
| Output $ / M tokens | — | $2.30 |
| Results tracked | 27 | 42 |
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Category by category
Coding Too close to call
GPT-5.5 Instant: 43.7 (#73), Kimi K2 (Jul 2025): 43.1 (#83)
| Benchmark | GPT-5.5 Instant | Kimi K2 (Jul 2025) |
|---|---|---|
| LMArena Coding | 1433 | 1399 |
| SWE-bench Verified (bash only) | — | 63.4% |
| Aider Polyglot | — | 59.1% |
| SciCode | 48.6% | — |
| GSO | — | 4.9% |
| WeirdML | — | 42.8% |
| ALE-Bench | — | 597.5 |
Agentic & Tool Use Not comparable
GPT-5.5 Instant: —, Kimi K2 (Jul 2025): 32.2 (#59)
| Benchmark | GPT-5.5 Instant | Kimi K2 (Jul 2025) |
|---|---|---|
| Terminal-Bench | — | 35.7% |
| Berkeley Function Calling Leaderboard | — | 59.1% |
| METR Time Horizons | — | 59.2% |
Reasoning GPT-5.5 Instant leads
GPT-5.5 Instant: 24.2 (#149), Kimi K2 (Jul 2025): 22.7 (#173)
| Benchmark | GPT-5.5 Instant | Kimi K2 (Jul 2025) |
|---|---|---|
| LMArena Hard Prompts | 1426 | 1384 |
| Epoch Capabilities Index | 142.48 | 146.02 |
| SimpleBench | — | 26.3% |
| Kagi LLM Benchmark | — | 64.4% |
| CritPt | 0% | — |
| Chess Puzzles | 12% | — |
| ForecastBench | — | 60.2 |
Math Kimi K2 (Jul 2025) leads
GPT-5.5 Instant: 26.1 (#241), Kimi K2 (Jul 2025): 40.1 (#81)
| Benchmark | GPT-5.5 Instant | Kimi K2 (Jul 2025) |
|---|---|---|
| LMArena Math | 1420 | 1396 |
| FrontierMath (Tiers 1-3) | 26.3% | — |
| FrontierMath Tier 4 | 2.4% | — |
| OTIS Mock AIME 2024-2025 | 68.1% | — |
| Omni-MATH | — | 65.4% |
| FrontierMath (Feb 2025 set) | — | 21.4% |
| FrontierMath Tier 4 (v1) | — | 0% |
Knowledge GPT-5.5 Instant leads
GPT-5.5 Instant: 48.9 (#68), Kimi K2 (Jul 2025): 36.9 (#153)
| Benchmark | GPT-5.5 Instant | Kimi K2 (Jul 2025) |
|---|---|---|
| LMArena Expert | 1409 | 1363 |
| GPQA Diamond | 82.5% | — |
| MMLU-Pro | — | 81.9% |
| Confabulations | — | 20.4% |
| Vectara Hallucination Rate | — | 17.9% |
| GPQA (HELM) | — | 65.3% |
Multimodal Not comparable
GPT-5.5 Instant: 39.3 (#48), Kimi K2 (Jul 2025): —
| Benchmark | GPT-5.5 Instant | Kimi K2 (Jul 2025) |
|---|---|---|
| LMArena Vision | 1250 | — |
| LMArena Document | 1403 | — |
Multilingual GPT-5.5 Instant leads
GPT-5.5 Instant: 53.0 (#76), Kimi K2 (Jul 2025): 49.8 (#125)
| Benchmark | GPT-5.5 Instant | Kimi K2 (Jul 2025) |
|---|---|---|
| LMArena Non-English | 1417 | 1372 |
| LMArena Chinese | 1457 | 1416 |
| LMArena French | 1428 | 1379 |
| LMArena German | 1410 | 1386 |
| LMArena Japanese | 1408 | 1349 |
| LMArena Korean | 1393 | 1324 |
| LMArena Russian | 1430 | 1384 |
| LMArena Spanish | 1430 | 1383 |
Instruction Following GPT-5.5 Instant leads
GPT-5.5 Instant: 74.4 (#94), Kimi K2 (Jul 2025): 71.3 (#151)
| Benchmark | GPT-5.5 Instant | Kimi K2 (Jul 2025) |
|---|---|---|
| LMArena Instruction Following | 1407 | 1347 |
| IFEval | — | 85% |
Long Context GPT-5.5 Instant leads
GPT-5.5 Instant: 43.4 (#92), Kimi K2 (Jul 2025): 41.2 (#140)
| Benchmark | GPT-5.5 Instant | Kimi K2 (Jul 2025) |
|---|---|---|
| LMArena Longer Query | 1422 | 1353 |
| Fiction.LiveBench | — | 66.7% |
| CL-bench | — | 17.6% |
Writing & Preference Too close to call
GPT-5.5 Instant: 62.0 (#81), Kimi K2 (Jul 2025): 62.5 (#76)
| Benchmark | GPT-5.5 Instant | Kimi K2 (Jul 2025) |
|---|---|---|
| LMArena Text | 1419 | 1380 |
| LMArena Creative Writing | 1420 | 1349 |
| LMArena Multi-Turn | 1434 | 1371 |
| Short-Story Creative Writing | — | 85.6% |
| EQ-Bench Creative Writing | — | 1666 |
| WildBench | — | 86.2% |
Frequently asked questions
Is GPT-5.5 Instant better than Kimi K2 (Jul 2025)?
GPT-5.5 Instant is the stronger model overall, scoring 42.5 to 40.9 on the Noometry Index.
Is GPT-5.5 Instant or Kimi K2 (Jul 2025) better for coding?
They score almost the same on coding (43.7 vs 43.1); test both on your own repository before choosing.
How many benchmarks do GPT-5.5 Instant and Kimi K2 (Jul 2025) share?
18 benchmarks have published results for both models. GPT-5.5 Instant has 27 scored results on Noometry and Kimi K2 (Jul 2025) has 42.