Which is cheaper, Grok-4 Fast Reasoning or Phi 4?
As of August 22, 2026, Phi 4 is 70% cheaper on blended LLM API pricing. Phi 4 costs $0.07 per million input tokens and $0.14 per million output tokens ($0.21 blended 1M-in + 1M-out). Grok-4 Fast Reasoning costs $0.20 / $0.50 per million tokens ($0.70 blended). Sources: https://docs.x.ai/docs/models and https://azure.microsoft.com/en-us/pricing/details/cognitive-services/openai-service/. The cheapest LLM for your app still depends on how many output tokens you generate.
How much does Grok-4 Fast Reasoning vs Phi 4 cost per million tokens?
Grok-4 Fast Reasoning xAI API pricing is $0.20 input and $0.50 output per million tokens via xAI. Phi 4 Microsoft API pricing is $0.07 input and $0.14 output per million tokens via Microsoft. Use those four numbers, not ChatGPT Plus or Claude Pro subscription prices, when you are comparing APIs.
Which is better for coding, Grok-4 Fast Reasoning or Phi 4?
Grok-4 Fast Reasoning has a published SWE-bench Verified score of 45.4%. Phi 4 does not have that eval on this page yet.
What is the context window for Grok-4 Fast Reasoning vs Phi 4?
Grok-4 Fast Reasoning supports a 2M token context window, while Phi 4 supports 16K tokens. Grok-4 Fast Reasoning offers a larger context window. Filling a larger window bills more input tokens, so the cheaper-per-million model can still cost more on long documents.
Which model performs better on benchmarks, Grok-4 Fast Reasoning or Phi 4?
Grok-4 Fast Reasoning leads on 4 of 4 shared benchmarks versus Phi 4's 0 wins. Check the comparison table for GPQA Diamond, SWE-bench, MMLU, HLE, and the other evals we track. Token price and benchmark score together are the usual LLM comparison, not either number alone.
Is Grok-4 Fast Reasoning or Phi 4 better for production use?
Both Grok-4 Fast Reasoning and Phi 4 are production API models. For cost-sensitive production traffic, Phi 4 has better economics on the blended 1M-in + 1M-out scale. For maximum capability, weight the benchmark table for your domain. Many production stacks route cheap models for drafts and a frontier model for the hard turn, which is usually cheaper than sending everything to the expensive API.
Can I switch between Grok-4 Fast Reasoning and Phi 4 in my app?
Yes. Call Grok-4 Fast Reasoning through xAI and Phi 4 through Microsoft with separate API keys, or through a gateway that already wraps both. Keep prompts in tokens, not characters, when you estimate the invoice. AnotherWrapper templates can swap providers without rewriting auth and billing.
How accurate is this Grok-4 Fast Reasoning vs Phi 4 pricing data?
List rates are the latest published xAI API pricing and Microsoft API pricing, quoted per million tokens. Official rate sheets: https://docs.x.ai/docs/models and https://azure.microsoft.com/en-us/pricing/details/cognitive-services/openai-service/. Prompt caching, batch APIs, and committed-use discounts can change the invoice. Benchmark scores are from official publications and independent evals, updated as new numbers land.
What is the output token limit for Grok-4 Fast Reasoning and Phi 4?
Grok-4 Fast Reasoning supports up to 30K output tokens per request, while Phi 4 supports up to 16K output tokens. Output tokens are usually the expensive half of API pricing, so a higher max output cap is a capability, not a discount.
Which model has better throughput, Grok-4 Fast Reasoning or Phi 4?
Grok-4 Fast Reasoning runs at approximately 90 tokens/second while Phi 4 runs at 33 tokens/second. Grok-4 Fast Reasoning is faster in raw throughput. Throughput (tokens per second) and time-to-first-token are why two models with the same per-million-token price can still feel different in chat and agents.
How do I switch the models in this Grok-4 Fast Reasoning vs Phi 4 comparison?
Use the model pickers at the top of this LLM comparison. Search any model in the index and the URL updates. Open Grok-4 Fast Reasoning or Phi 4 from the sidebar for the single-model API pricing page, or go back to the LLM pricing table to sort by cheapest blended cost.
