High-volume, cost-sensitive work
Choose Gemini 3 Flash
Gemini 3 Flash costs 28% less on a typical mix of three input tokens for every output token ($1.13 against $1.56 per million tokens).
Gemini 3 Flash vs Grok 4.20 Reasoning: price, context and capabilities
Choose Gemini 3 Flash for high-volume, cost-sensitive work and reused prompts and documents (RAG, agents). Choose Grok 4.20 Reasoning for writing and code generation and the latest release.
In short
- Gemini 3 Flash is 28% cheaper than Grok 4.20 Reasoning at the headline price ($1.13 / 1M tokens vs $1.56 / 1M tokens).
- Gemini 3 Flash reads more per request: 1.05M tokens against 1M.
- Grok 4.20 Reasoning is the newer model (March 2026, against December 2025).
Which should you choose?
Each answer below comes straight from the published prices, specifications and independent benchmark results.
Writing and code generation
Choose Grok 4.20 Reasoning
Grok 4.20 Reasoning charges $2.50 per million output tokens, against $3.00 for Gemini 3 Flash. Output dominates the bill when answers are long.
Reused prompts and documents (RAG, agents)
Choose Gemini 3 Flash
Gemini 3 Flash charges $0.05 per million cached input tokens, against $0.20 for Grok 4.20 Reasoning.
Latest release
Choose Grok 4.20 Reasoning
Grok 4.20 Reasoning is the newer release (March 2026, against December 2025 for Gemini 3 Flash).
Monthly cost at three volumes
| Volume | Gemini 3 Flash | Grok 4.20 Reasoning | Difference |
|---|---|---|---|
| Prototype: 1M input, 250K output tokens | $1.25 | $1.88 | Gemini 3 Flash, $0.63 less |
| Production: 20M input, 5M output tokens | $25.00 | $37.50 | Gemini 3 Flash, $12.50 less |
| Scale: 500M input, 100M output tokens | $550.00 | $875.00 | Gemini 3 Flash, $325.00 less |
Standard rates, without caching or batch discounts. Volumes are per month.
Specifications side by side
| Gemini 3 Flash | Grok 4.20 Reasoning | |
|---|---|---|
| Provider | xAI | |
| Category | Language models | Language models |
| Status | Legacy | Generally available |
| Headline price | $1.13 / 1M tokens | $1.56 / 1M tokens |
| Input | $0.50 / 1M tokens | $1.25 / 1M tokens |
| Output | $3.00 / 1M tokens | $2.50 / 1M tokens |
| Cached input | $0.05 / 1M tokens | $0.20 / 1M tokens |
| Context window | 1.05M | 1M |
| Max output | 66k | No data |
| Released | December 2025 | March 2026 |
| Knowledge cutoff | No data | No data |
| Licence | Proprietary | Proprietary |
| Capabilities | Vision, Reasoning, Tool calling, Structured output, Prompt caching, Batch API | Vision, Reasoning, Tool calling, Structured output, Prompt caching, Batch API |
| API model id | gemini-3-flash-preview | grok-4.20-0309-reasoning |
Frequently asked questions
Should I choose Gemini 3 Flash or Grok 4.20 Reasoning?
Choose Gemini 3 Flash for high-volume, cost-sensitive work and reused prompts and documents (RAG, agents). Choose Grok 4.20 Reasoning for writing and code generation and the latest release.
Which is cheaper, Gemini 3 Flash or Grok 4.20 Reasoning?
Gemini 3 Flash is 28% cheaper than Grok 4.20 Reasoning at the headline price ($1.13 / 1M tokens vs $1.56 / 1M tokens).
Which has the larger context window, Gemini 3 Flash or Grok 4.20 Reasoning?
Gemini 3 Flash reads more per request: 1.05M tokens against 1M.
What is the difference between Gemini 3 Flash and Grok 4.20 Reasoning?
Gemini 3 Flash is made by Google and Grok 4.20 Reasoning by xAI. Gemini 3 Flash is 28% cheaper than Grok 4.20 Reasoning at the headline price ($1.13 / 1M tokens vs $1.56 / 1M tokens). Gemini 3 Flash reads more per request: 1.05M tokens against 1M. Grok 4.20 Reasoning is the newer model (March 2026, against December 2025).
How much do Gemini 3 Flash and Grok 4.20 Reasoning cost per month?
At 20 million input and 5 million output tokens a month, Gemini 3 Flash costs $25.00 and Grok 4.20 Reasoning costs $37.50, at standard rates.
Which is newer, Gemini 3 Flash or Grok 4.20 Reasoning?
Grok 4.20 Reasoning was released on March 2026 and Gemini 3 Flash on December 2025.