As of August 20, 2026, Grok-4 Fast Reasoning is 91% cheaper per million tokens than Grok 4.6. Grok-4 Fast Reasoning is $0.20 / $0.50 per million input/output tokens versus Grok 4.6 at $2.00 / $6.00. Source: https://docs.x.ai/docs/models
Source: xAI API pricing (https://docs.x.ai/docs/models)
Grok-4 Fast Reasoning
xAI
Input
$0.20
Output
$0.50
Grok 4.6
xAI
Input
$2.00
Output
$6.00
Token pricing, specs, and benchmarks side by side
Grok-4 Fast ReasoningGrok 4.6Verdict
Grok-4 Fast Reasoning offers significantly lower pricing, while Grok 4.6 leads on benchmark performance. Your choice depends on whether cost efficiency or raw capability matters more for your use case.
As of August 20, 2026, Grok-4 Fast Reasoning is 91% cheaper on blended LLM API pricing. Grok-4 Fast Reasoning costs $0.20 per million input tokens and $0.50 per million output tokens ($0.70 blended 1M-in + 1M-out). Grok 4.6 costs $2.00 / $6.00 per million tokens ($8.00 blended). Sources: https://docs.x.ai/docs/models and https://docs.x.ai/docs/models. The cheapest LLM for your app still depends on how many output tokens you generate.
Grok-4 Fast Reasoning xAI API pricing is $0.20 input and $0.50 output per million tokens via xAI. Grok 4.6 xAI API pricing is $2.00 input and $6.00 output per million tokens via xAI. Use those four numbers, not ChatGPT Plus or Claude Pro subscription prices, when you are comparing APIs.
Grok 4.6 leads on SWE-bench Verified: Grok-4 Fast Reasoning at 45.4% vs Grok 4.6 at 95.6%. SWE-bench measures real GitHub fixes; LiveCodeBench measures contest programming.
Grok-4 Fast Reasoning supports a 2M token context window, while Grok 4.6 supports 500K 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.
Grok 4.6 leads on 11 of 14 shared benchmarks versus Grok-4 Fast Reasoning's 3 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.
Both Grok-4 Fast Reasoning and Grok 4.6 are production API models. For cost-sensitive production traffic, Grok-4 Fast Reasoning 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.
Yes. Call Grok-4 Fast Reasoning through xAI and Grok 4.6 through xAI 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.
List rates are the latest published xAI API pricing and xAI API pricing, quoted per million tokens. Official rate sheets: https://docs.x.ai/docs/models and https://docs.x.ai/docs/models. 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.
Grok-4 Fast Reasoning supports up to 30K output tokens per request, while Grok 4.6 supports up to an unspecified number of output tokens. Output tokens are usually the expensive half of API pricing, so a higher max output cap is a capability, not a discount.
Grok-4 Fast Reasoning runs at approximately 90 tokens/second while Grok 4.6 runs at 4.687848222704461 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.
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 Grok 4.6 from the sidebar for the single-model API pricing page, or go back to the LLM pricing table to sort by cheapest blended cost.
This comparison covers API pricing, context window, throughput, and benchmark scores. Grok-4 Fast Reasoning costs $0.20/M input and $0.50/M output. Grok 4.6 costs $2.00/M input and $6.00/M output.
Rank both on the LLM leaderboard, SWE-bench, and Humanity's Last Exam.
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