Kimi K2 Thinking vs GPT-5.1 Chat
Kimi K2 Thinking comes out ahead, 42 to 38 on our weighted score, and it is the cheaper option too.
- Our pick
Moonshot AIKimi K2 Thinking
42/100- ECI146.0
- Price$0.60 / $2.50
- Context262K
OpenAIGPT-5.1 Chat
38/100- ECI—
- Price$1.25 / $10.00
- Context128K
Add a model
Make it a three-way comparison.
Kimi K2 Thinking is our pick
Kimi K2 Thinking is the better all-round choice, scoring 42/100 against GPT-5.1 Chat (38). It leads on price and context window. GPT-5.1 Chat wins on inputs & features. The score weighs price 50%, inputs & features 30%, context window 20%. None of the shared benchmarks cover every model here yet, so capability is left out of this verdict.
- CapabilityNot enough dataNo independent benchmark covers every model here yet
- Lowest priceKimi K2 ThinkingKimi K2 Thinking $1.07 · GPT-5.1 Chat $3.44 per 1M tokens (3:1 blend)
- Longest contextKimi K2 ThinkingKimi K2 Thinking 262,144 · GPT-5.1 Chat 128,000 tokens
- Widest inputsGPT-5.1 ChatKimi K2 Thinking: Text · GPT-5.1 Chat: Text, Images
- Self-hostingKimi K2 ThinkingPublishes downloadable weights
| Measure | Weight | Kimi K2 Thinking | GPT-5.1 Chat |
|---|---|---|---|
| Price | 50% | 48 | 24 |
| Inputs & features | 30% | 35 | 70 |
| Context window | 20% | 37 | 24 |
| Overall | 100% | 42/100 | 38/100 |
Left out because at least one model lacks the data: capability. The remaining weights were rescaled.
Every spec in one table
Highlighted cells lead their row. Dashes mean the data is not published.
| Specification | Kimi K2 ThinkingMoonshot AI | GPT-5.1 ChatOpenAI |
|---|---|---|
| Capability | ||
| Capabilities Index (ECI) | 146.0 | — |
| ECI rank | #72 of 148 | — |
| GPQA DiamondGraduate-level science questions | 84.2% | — |
| OTIS Mock AIME 2024–2025Competition mathematics | 83.1% | — |
| Price per million tokens | ||
| Input | $0.60 (best) | $1.25 |
| Output | $2.50 (best) | $10.00 |
| Cached input | — | — |
| Blended (3:1) | $1.07 (best) | $3.44 |
| Long-context rate | Same rate | Same rate |
| Price source | Median of 10 providers | Median of 2 providers |
| Limits | ||
| Context window | 262,144 tokens (best) | 128,000 tokens |
| Max output | 262,144 tokens (best) | 16,384 tokens |
| Inputs and features | ||
| Text | Yes | Yes |
| Images | No | Yes |
| PDFs | No | No |
| Audio | No | No |
| Video | No | No |
| Reasoning | Yes | Yes |
| Tool calling | Yes | Yes |
| Structured output | No | Yes |
| Availability | ||
| Weights | Open | Proprietary |
| API model ID | — | — |
| API providers | 10 (best) | 2 |
| Released | Nov 6, 2025 | Nov 13, 2025 |
| Knowledge cutoff | Aug 2024 | Sep 30, 2024 |
What would a month cost?
Enter your expected volume in millions of tokens. List prices only; caching and batch discounts would lower these.
- Kimi K2 Thinking$11.00
- GPT-5.1 Chat$32.50
Which should you choose?
Which is better: Kimi K2 Thinking or GPT-5.1 Chat?
Kimi K2 Thinking is the better all-round choice, scoring 42/100 against GPT-5.1 Chat (38). It leads on price and context window. GPT-5.1 Chat wins on inputs & features. The score weighs price 50%, inputs & features 30%, context window 20%. None of the shared benchmarks cover every model here yet, so capability is left out of this verdict.
Which is cheaper, Kimi K2 Thinking or GPT-5.1 Chat?
Kimi K2 Thinking is cheaper at $0.60 input / $2.50 output per million tokens (median across 10 API providers). GPT-5.1 Chat costs $1.25 input / $10.00 output per million tokens (median across 2 API providers). At a typical mix of three input tokens to one output token, that is $1.07 per million tokens for Kimi K2 Thinking versus $3.44 for GPT-5.1 Chat (3.2× as much).
Which scores higher on benchmarks?
There is no independent benchmark that covers both models yet. Kimi K2 Thinking has an ECI of 146.0 and GPT-5.1 Chat has not been scored yet.
Which is better for coding?
There are no published SWE-bench Verified results for Kimi K2 Thinking and GPT-5.1 Chat yet, so there is no like-for-like coding score. Test both on a sample of your own tasks. Both support tool calling for agent workflows.
Which has the bigger context window?
Kimi K2 Thinking has the largest context window at 262,144 tokens, against 128,000 for GPT-5.1 Chat. Maximum output per response: Kimi K2 Thinking up to 262,144, GPT-5.1 Chat up to 16,384 tokens.
Which can read images, PDFs, audio or video?
Kimi K2 Thinking accepts text; GPT-5.1 Chat accepts text and images. GPT-5.1 Chat handles the widest range of inputs.
Are any of these open source?
Kimi K2 Thinking publishes its weights and can be self-hosted; GPT-5.1 Chat is proprietary.
Which is newer?
GPT-5.1 Chat is the newest, released Nov 13, 2025. Kimi K2 Thinking came out Nov 6, 2025. Knowledge cutoff: Kimi K2 Thinking Aug 2024, GPT-5.1 Chat Sep 30, 2024.
How do you decide the winner?
Each model gets a 0–100 score on capability (50%, independent benchmark results); price (25%, blended price per million tokens (3 input : 1 output), log scale); inputs & features (15%, image, PDF, audio and video input, tool calling, structured output and reasoning); context window (10%, maximum tokens per request, log scale). Dimensions missing for any model are dropped and the remaining weights rescaled, so every model is judged on the same evidence. Specs and prices come from public model listings and the labs’ own API pages; capability scores come from independent benchmark runs. Data updated Oct 4, 2026.
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