Grok 4 Fast API Pricing
Grok 4 Fast is now an archive row: historical pricing was $0.20/M input, $0.05/M cached input, and $0.50/M output. SpaceXSI's May 15 retirement guide says retired Fast slugs redirect to Grok 4.3.
Grok 4 Fast API cost calculator.
Calculator pre-loaded with Grok 4 Fast archive rates. After May 15, 2026, SpaceXSI (formerly xAI) routes retired fast slugs to Grok 4.3 pricing.
Grok 4 Fast cost on real workloads.
Invoice replay
Legacy agent task
Migration cost comparison
Archived RAG answer
This is a chars-per-token approximation, not a real tokenizer. Actual tokens vary by language, code density, and tool-call overhead — counts are typically ±10–20% off for English prose, more for code or non-Latin scripts. For exact billing, use the vendor's official tokenizer.
| Model | Input /M | Output /M | Effective blended | Context | Best for |
|---|---|---|---|---|---|
| Grok 4 Fast Current | $0.20 cache $0.05 | $0.50 | $0.111 agentic 92/8 | 2M | Archive fast-tier invoices |
| Grok 4.3 | $1.25 cache $0.20 | $2.50 | $0.558 +5.0× | 1M | Current Grok default |
| Gemini 3.8 Flash | $0.75 cache $0.075 | $3.75 | $0.481 +4.3× · promo | 1M | Mainstream multimodal work |
| GPT-6.1 Terra | $1.00 cache $0.05 | $5.00 | $0.645 +5.8× | 1.05M | OpenAI's fast, efficient GPT-6 tier |
| DeepSeek V4 Pro | $1.32 cache $0.044 | $3.96 | $0.569 +5.1× | 1M | Low-cost reasoning alternative |
Grok 4 Fast has published scores on 2 benchmarks we track; its best placing is #70 of 105 on ARC-AGI-2. All of these scores come from independent leaderboards, not from the lab.
| Benchmark | Score | Rank | Leader | Source |
|---|---|---|---|---|
| ARC-AGI-2 Reasoning | 5.3% ARC Prize verified, best result | #70 of 105 | GPT-6 Astra · 95% | Official leaderboard ARC Prize Foundation |
| ARC-AGI-1 Reasoning | 48.5% ARC Prize verified, best result | #70 of 99 | 6 tied · 98.5% | Official leaderboard ARC Prize Foundation |
Grok 4 Fast API pricing FAQ.
Grok 4 Fast pricing questions, with archive status separated from token math.
Q · 01 What was Grok 4 Fast's API price? +
$0.2/M input, $0.05/M cached input, and $0.5/M output. Use it for historical billing and migration math, not fresh production routing.Q · 02 Is Grok 4 Fast still available? +
grok-4-fast-reasoning and grok-4-fast-non-reasoning as retired. After retirement, requests redirect to grok-4.3.Q · 03 What should replace it? +
grok-4.3. SpaceXSI's current pricing page lists Grok 4.3 at $1.25/M input, $0.20/M cached input, and $2.50/M output.Q · 04 Does prompt caching apply? +
$0.05/M. The effective blend assumes 82% cache hits; set cache to off in the calculator for fresh-input workloads.Q · 05 Why keep an archive page? +
Q · 06 How accurate is the tokenizer estimate? +
4.875 characters per token as a planning estimate. Exact billing can vary with language, hidden reasoning, cached prompt boundaries, and tool usage.