text model comparison
Gemini 3.8 Flash vs Grok 4.20
Gemini 3.8 Flash and Grok 4.20 are both current text models, from Google and xAI. Gemini 3.8 Flash is 40% cheaper per 1M input tokens than Grok 4.20, $0.75 vs $1.25. On Arena Text, Gemini 3.8 Flash scores 1497 Elo and Grok 4.20 1472 Elo (Arena, measured October 8, 2026). Both accept about 1.05M tokens of context (1,048,576 and 1,000,000).
Data verified October 12, 2026 · Dataset 2026-10-12
Side by side
Standard-tier prices in effect today. The better value in each row is highlighted.
| Fact | Gemini 3.8 Flash | Grok 4.20 |
|---|---|---|
| Price per 1M input tokens | $0.75 (better) | $1.25 |
| Price per 1M output tokens | $3.75 | $2.50 (better) |
| Cost of 10M input and 2M output tokens | $15 (better) | $17.50 |
| Arena Text | 1497 Elo (#4 of 39) (better) | 1472 Elo (#22 of 39) |
| GPQA Diamond | 95.4% (#3 of 37) (better) | 89.3% (#28 of 37) |
| FrontierMath Tiers 1-3 (v2) | 68.4% (#21 of 37) (better) | 44.9% (#31 of 37) |
| SimpleQA Verified | 69.7% (#7 of 34) (better) | 30.2% (#30 of 34) |
| Provider | xAI | |
| Release date | September 2, 2026 | March 10, 2026 |
| Access | API only | API only |
| Context window | 1,048,576 tokens | 1,000,000 tokens |
| Max output | 65,536 tokens | Not reported |
| Input | text, image, audio, video | text, image |
| Output | text | text |
When to choose each
Gemini 3.8 Flash
Best for
- High-volume agentic and coding workloads where per-token cost dominates the decision
- Multimodal pipelines that need audio, video and PDF input in one model
Watch out for
- The listed price is promotional and ends 31 December 2026; on 1 January 2027 input and output both double, to $1.50 and $7.50, and cached input goes from $0.075 to $0.15
- Output pricing is billed inclusive of thinking tokens, so reasoning-heavy prompts cost more than the output length suggests
- Google’s published comparisons are against its own previous Flash release and were not independently reproduced here
Grok 4.20
Best for
- Comparing single-agent and multi-agent reasoning on long-context workloads
Watch out for
- The published base rates double when requests reach the provider's 200,000-token long-context threshold
Gemini 3.8 Flash vs Grok 4.20 FAQ
Which is cheaper, Gemini 3.8 Flash or Grok 4.20?
Gemini 3.8 Flash is 40% cheaper per 1M input tokens than Grok 4.20, $0.75 vs $1.25. For 10M input and 2M output tokens, Gemini 3.8 Flash costs $15 and Grok 4.20 $17.50 at standard rates.
Which scores higher on independent benchmarks, Gemini 3.8 Flash or Grok 4.20?
Gemini 3.8 Flash leads on Arena Text, 1497 Elo to 1472 Elo; Gemini 3.8 Flash leads on GPQA Diamond, 95.4% to 89.3%; Gemini 3.8 Flash leads on FrontierMath Tiers 1-3 (v2), 68.4% to 44.9%. Scores are independent evaluations, not either vendor's launch figures.
Which has the larger context window, Gemini 3.8 Flash or Grok 4.20?
Both accept about 1.05M tokens of context (1,048,576 and 1,000,000).
Related comparisons
- Claude Opus 4.8 vs Gemini 3.8 Flash
- Claude Opus 5.5 vs Gemini 3.8 Flash
- Claude Opus 5 vs Gemini 3.8 Flash
- Claude Sonnet 5.5 vs Gemini 3.8 Flash
- DeepSeek-V4.1-Flash vs Gemini 3.8 Flash
- DeepSeek-V4.1-Flash vs Grok 4.20
- Gemini 3.1 Pro Preview vs Grok 4.20
- Gemini 3.6 Flash vs Gemini 3.8 Flash
- Gemini 3.6 Flash vs Grok 4.20
- Gemini 3.7 Flash vs Gemini 3.8 Flash
Production evaluation
Choosing between Gemini 3.8 Flash and Grok 4.20?
Public benchmarks narrow the shortlist. We run both on your own tasks, data and cost limits, then build the routing and review controls to run the winner in production.
- A head-to-head evaluation on your real workload
- Routing between models by cost and difficulty