Kimi K3 vs GPT-5.1
Detailed pricing comparison and cost analysis.
Updated September 2026
Cost Simulator
| Feature | Kimi K3 | GPT-5.1 |
|---|---|---|
| Provider | Moonshot AI | OpenAI |
| Input Price (1M) | $3.00 | $1.25 |
| Output Price (1M) | $15.00 | $10.00 |
| Context Window | 1,000,000 | 400,000 |
Verdict
Kimi K3 costs $3.00 per 1M input tokens and $15.00 per 1M output tokens. GPT-5.1 costs $1.25 per 1M input tokens and $10.00 per 1M output tokens. GPT-5.1 is 58% cheaper on input tokens than Kimi K3. For output tokens, GPT-5.1 is the more affordable option at $10.00/1M vs $15.00.
On context window, Kimi K3 supports 1,000,000 tokens — meaning it can fit more conversation history, documents, or code in a single request. This matters for RAG pipelines, long document analysis, and agentic workflows where context builds up over many turns.
When to choose Kimi K3
- ✓ You need a larger context window (1,000,000 tokens)
- ✓ You are already integrated with Moonshot AI
When to choose GPT-5.1
- ✓ You need the lowest input token cost ($ 1.25/1M)
- ✓ Your workload is output-heavy — GPT-5.1 generates text cheaper
- ✓ You are already integrated with OpenAI
Use the calculator above to simulate your specific workload and find the exact break-even point. For most applications, the cheapest model is the one that minimises your total monthly bill given your input-to-output token ratio.
Frequently Asked Questions
Is Kimi K3 cheaper than GPT-5.1? ▼
GPT-5.1 is cheaper on input tokens at $1.25/1M vs $3.00/1M for Kimi K3 — a 58% saving.
What is the context window of Kimi K3 vs GPT-5.1? ▼
Kimi K3 has a 1,000,000-token context window. GPT-5.1 has a 400,000-token context window. Kimi K3 supports the larger context, suitable for longer documents and agentic workflows.
Which model is better: Kimi K3 or GPT-5.1? ▼
The best choice depends on your use case. For cost efficiency on input tokens, GPT-5.1 is the cheaper option. For maximum context length, Kimi K3 supports 1,000,000 tokens. Use the comparison table above to find the right fit for your workload.