Claude Sonnet 4.5 vs Phi-3 Mini 4k
Claude Sonnet 4.5 (2025) and Phi-3 Mini 4k (2024) are frontier reasoning models from Anthropic and Microsoft Research. Claude Sonnet 4.5 ships a 200K-token context window, while Phi-3 Mini 4k ships a 4K-token context window. On MMLU PRO, Claude Sonnet 4.5 leads by 40.3 pts. On pricing, Phi-3 Mini 4k costs $0.05/1M input tokens versus $3/1M for the alternative. This comparison covers specs, pricing, capabilities, benchmarks, provider availability, and production fit.
Phi-3 Mini 4k is ~5900% cheaper at $0.05/1M; pay for Claude Sonnet 4.5 only for reasoning depth.
Specs
| Released | 2025-09-29 | 2024-04-23 |
| Context window | 200K | 4K |
| Parameters | — | 3.8B |
| Architecture | decoder only | decoder only |
| License | Proprietary | Open Source |
| Knowledge cutoff | 2025-12 | - |
Pricing and availability
| Claude Sonnet 4.5 | Phi-3 Mini 4k | |
|---|---|---|
| Input price | $3/1M tokens | $0.05/1M tokens |
| Output price | $15/1M tokens | $0.25/1M tokens |
| Providers |
Capabilities
| Claude Sonnet 4.5 | Phi-3 Mini 4k | |
|---|---|---|
| Vision | ||
| Multimodal | ||
| Reasoning | ||
| Function calling | ||
| Tool use | ||
| Structured outputs | ||
| Code execution |
Benchmarks
| Benchmark | Claude Sonnet 4.5 | Phi-3 Mini 4k |
|---|---|---|
| MMLU PRO | 86.0 | 45.7 |
Deep dive
On shared benchmark coverage, MMLU PRO has Claude Sonnet 4.5 at 86 and Phi-3 Mini 4k at 45.7, with Claude Sonnet 4.5 ahead by 40.3 points. The largest visible gap is 40.3 points on MMLU PRO, which matters most when that benchmark mirrors your workload. Treat isolated benchmark wins as directional, because provider routing, prompt style, and tool access can move real application results.
The capability footprint differs most on vision: Claude Sonnet 4.5, multimodal input: Claude Sonnet 4.5, reasoning mode: Claude Sonnet 4.5, function calling: Claude Sonnet 4.5, tool use: Claude Sonnet 4.5, and structured outputs: Claude Sonnet 4.5. Both models share the core language-model surface, so the practical split is not just feature count. Use those differences to decide whether the page is about raw model quality, agentic coding support, multimodal ingestion, or predictable structured API behavior.
For cost, Claude Sonnet 4.5 lists $3/1M input and $15/1M output tokens, while Phi-3 Mini 4k lists $0.05/1M input and $0.25/1M output tokens on the cheapest tracked provider. A 70/30 input-output blend puts Phi-3 Mini 4k lower by about $6.49 per million blended tokens. Availability is 8 providers versus 4, so concentration risk also matters.
Choose Claude Sonnet 4.5 when reasoning depth, larger context windows, and broader provider choice are central to the workload. Choose Phi-3 Mini 4k when provider fit and lower input-token cost are more important. For production, rerun your own prompts through the exact provider, region, and tool stack you plan to ship.
FAQ
Which has a larger context window, Claude Sonnet 4.5 or Phi-3 Mini 4k?
Claude Sonnet 4.5 supports 200K tokens, while Phi-3 Mini 4k supports 4K tokens. That gap matters most for long documents, large codebases, retrieval-heavy agents, and conversations where earlier context must remain visible.
Which is cheaper, Claude Sonnet 4.5 or Phi-3 Mini 4k?
Phi-3 Mini 4k is cheaper on tracked token pricing. Claude Sonnet 4.5 costs $3/1M input and $15/1M output tokens. Phi-3 Mini 4k costs $0.05/1M input and $0.25/1M output tokens. Provider discounts or batch pricing can still change the final bill.
Is Claude Sonnet 4.5 or Phi-3 Mini 4k open source?
Claude Sonnet 4.5 is listed under Proprietary. Phi-3 Mini 4k is listed under Open Source. License labels affect whether you can self-host, redistribute weights, or rely only on hosted APIs, so confirm the upstream license before deployment.
Which is better for vision, Claude Sonnet 4.5 or Phi-3 Mini 4k?
Claude Sonnet 4.5 has the clearer documented vision signal in this comparison. If vision is mission-critical, validate it against the provider endpoint because model-level support and API-level exposure can differ.
Which is better for multimodal input, Claude Sonnet 4.5 or Phi-3 Mini 4k?
Claude Sonnet 4.5 has the clearer documented multimodal input signal in this comparison. If multimodal input is mission-critical, validate it against the provider endpoint because model-level support and API-level exposure can differ.
Where can I run Claude Sonnet 4.5 and Phi-3 Mini 4k?
Claude Sonnet 4.5 is available on Microsoft Foundry, Anthropic, Snowflake Cortex, GCP Vertex AI, and AWS Bedrock. Phi-3 Mini 4k is available on Microsoft Foundry, NVIDIA NIM, Baseten API, and Replicate API. Provider coverage can affect latency, region availability, compliance posture, and fallback options.
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Last reviewed: 2026-04-24. Data sourced from public model cards and provider documentation.