o3 Mini vs Phi-3 Mini 4k
o3 Mini (2025) and Phi-3 Mini 4k (2024) are frontier reasoning models from OpenAI and Microsoft Research. o3 Mini ships a 200k-token context window, while Phi-3 Mini 4k ships a 4k-token context window. On MMLU PRO, o3 Mini leads by 33.4 pts. On pricing, Phi-3 Mini 4k costs $0.05/1M input tokens versus $1.10/1M for the alternative. This comparison covers specs, pricing, API access, capabilities, benchmarks, input and output token costs, and production fit for coding and agent workloads.
Phi-3 Mini 4k is ~2100% cheaper at $0.05/1M; pay for o3 Mini only for coding workflow support.
Decision scorecard
Local evidence first| Signal | o3 Mini | Phi-3 Mini 4k |
|---|---|---|
| Best for | reasoning-heavy apps, tool-calling agents, and provider-routed production | provider-routed production |
| Decision fit | Coding, RAG, and Agents | Coding and Classification |
| Context window | 200k | 4k |
| Cheapest output | $4.40/1M tokens | $0.25/1M tokens |
| Provider routes | 4 tracked | 4 tracked |
| Shared benchmarks | MMLU PRO leader | 2 rows |
Decision tradeoffs
- o3 Mini holds a shared-benchmark lead on MMLU PRO, ahead by 33.4 points.
- o3 Mini has the larger context window for long prompts, retrieval packs, or transcript analysis.
- o3 Mini uniquely exposes Reasoning, Function calling, and Tool use in local model data.
- Local decision data tags o3 Mini for Coding, RAG, and Agents.
- Phi-3 Mini 4k has the lower cheapest tracked output price at $0.25/1M tokens.
- Local decision data tags Phi-3 Mini 4k for Coding and Classification.
Monthly cost at traffic
Estimate token spend from the cheapest tracked input and output route or tier on this page.
o3 Mini
$1,980
Cheapest tracked route/tier: OpenRouter
Phi-3 Mini 4k
$103
Cheapest tracked route/tier: Replicate API
Estimated monthly gap: $1,878. Batch, cache, alternate speed tiers, and negotiated pricing are excluded from this local estimate.
Switch friction
- No overlapping tracked provider route is sourced for o3 Mini and Phi-3 Mini 4k; plan for SDK, billing, or endpoint changes.
- Phi-3 Mini 4k is $4.15/1M tokens lower on cheapest tracked output pricing before cache, batch, or negotiated discounts.
- Check replacement coverage for Reasoning, Function calling, and Tool use before moving production traffic.
- No overlapping tracked provider route is sourced for Phi-3 Mini 4k and o3 Mini; plan for SDK, billing, or endpoint changes.
- o3 Mini is $4.15/1M tokens higher on cheapest tracked output pricing, so quality gains need to justify the spend.
- o3 Mini adds Reasoning, Function calling, and Tool use in local capability data.
Specs
| Specification | ||
|---|---|---|
| Released | 2025-01-31 | 2024-04-23 |
| Context window | 200k | 4k |
| Parameters | — | 3.8B |
| Architecture | decoder only | decoder only |
| License | Proprietary | MIT(OSI) |
| Openness | Proprietary | Open source |
| Commercial use | Commercial use with conditions | Commercial use allowed |
| Knowledge cutoff | 2025-04 | 2023-10 |
Pricing and availability
| Pricing attribute | o3 Mini | Phi-3 Mini 4k |
|---|---|---|
| Input price | $1.10/1M tokens | $0.05/1M tokens |
| Output price | $4.40/1M tokens | $0.25/1M tokens |
| Providers |
Capabilities
| Capability | o3 Mini | Phi-3 Mini 4k |
|---|---|---|
| Vision | No | No |
| Multimodal | No | No |
| Reasoning | Yes | No |
| Function calling | Yes | No |
| Tool use | Yes | No |
| Structured outputs | Yes | No |
| Code execution | Yes | No |
| IDE integration | No | No |
| Computer use | No | No |
| Parallel agents | No | No |
Benchmarks
| Benchmark | o3 Mini | Phi-3 Mini 4k |
|---|---|---|
| MMLU PRO | 79.1 | 45.7 |
| Google-Proof Q&A | 79.7 | 40.9 |
Deep dive
On shared benchmark coverage, MMLU PRO has o3 Mini at 79.1 and Phi-3 Mini 4k at 45.7, with o3 Mini ahead by 33.4 points; Google-Proof Q&A has o3 Mini at 79.7 and Phi-3 Mini 4k at 40.9, with o3 Mini ahead by 38.8 points. The largest visible gap is 38.8 points on Google-Proof Q&A, 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 reasoning mode: o3 Mini, function calling: o3 Mini, tool use: o3 Mini, structured outputs: o3 Mini, and code execution: o3 Mini. 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, o3 Mini lists $1.10/1M input and $4.40/1M output tokens on the cheapest tracked provider, 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 $1.98 per million blended tokens. Availability is 4 providers versus 4, so concentration risk also matters.
Choose o3 Mini when coding workflow support and larger context windows 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, o3 Mini or Phi-3 Mini 4k?
o3 Mini 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, o3 Mini or Phi-3 Mini 4k?
Phi-3 Mini 4k is cheaper on tracked token pricing. o3 Mini costs $1.10/1M input and $4.40/1M 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 o3 Mini or Phi-3 Mini 4k open source?
o3 Mini is listed under Proprietary. Phi-3 Mini 4k is listed under MIT. 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 reasoning mode, o3 Mini or Phi-3 Mini 4k?
o3 Mini has the clearer documented reasoning mode signal in this comparison. If reasoning mode is mission-critical, validate it against the provider endpoint because model-level support and API-level exposure can differ.
Which is better for function calling, o3 Mini or Phi-3 Mini 4k?
o3 Mini has the clearer documented function calling signal in this comparison. If function calling is mission-critical, validate it against the provider endpoint because model-level support and API-level exposure can differ.
Where can I run o3 Mini and Phi-3 Mini 4k?
o3 Mini is available on OpenRouter, Azure OpenAI, OpenAI API, and Vercel AI Gateway. 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.
Continue comparing
Last reviewed: 2026-06-04. Data sourced from public model cards and provider documentation.