API cost decision in 10 seconds

New🔥Gemini 3.5 Flash vs Grok 4.20

Pick Grok 4.20 when budget and context both matter.

Page updated: 2026-05-26T12:03:47Z Data confirmed: 2026-05-26T12:43:06Z Prices normalized to USD per 1M tokens Sample workload: 1M input + 500K output

Budget verdict

Pick Grok 4.20 when budget and context both matter.

On the standard 1M input plus 500K output workload, Grok 4.20 is estimated at $2.5 vs $6 for Gemini 3.5 Flash, saving $3.5 (58.3% lower).

Cost-first pickGrok 4.20

Context-first pickGrok 4.20

Sample savings$3.558.3%

10x traffic gap$35

Grok 4.20 is cheaper on the standard workload and also has the larger context window. At 10x that traffic, the same price gap is about $35. Use the calculator below to replace the sample workload with your own token volume.

Cost sensitivity

Workload Sensitivity

Same prices, different token mixes.

Grok 4.20 stays cheaper across input-heavy, balanced, and output-heavy sample workloads.

Workload shape	Token mix	Better pick	Gemini 3.5 Flash	Grok 4.20
Input-heavy / RAG	5M input + 500K output	Grok 4.20	$12	$7.5
Balanced workload	1M input + 1M output	Grok 4.20	$10.5	$3.75
Output-heavy chatbot	1M input + 5M output	Grok 4.20	$46.5	$13.75

Cheaper input Grok 4.20 $1.5 vs $1.25 / 1M

Grok 4.20 is $0.25 cheaper per 1M input tokens (16.7% lower; 1.2x difference).

Cheaper output Grok 4.20 $9 vs $2.5 / 1M

Grok 4.20 is $6.5 cheaper per 1M output tokens (72.2% lower; 3.6x difference).

Larger context Grok 4.20 1.05M vs 2M

Grok 4.20 has 951.42K more context (1.91x larger).

Sample workload Grok 4.20 $6 vs $2.5

Grok 4.20 is $3.5 cheaper on the standard workload (58.3% lower).

Estimate your workload cost

Your Workload Cost

Prices are normalized to USD per 1M tokens.

Monthly input tokens Monthly output tokens

Gemini 3.5 Flash Calculating… Estimated API cost

Grok 4.20 Calculating… Estimated API cost

Cheaper for this workload Calculating… Difference: calculating…

This estimate uses normalized public API pricing per 1M tokens. It is a planning aid, not a billing quote. Verify provider pricing, limits, and terms before production use.

Quick Decision

Verdict

Grok 4.20 has the lower input price; Grok 4.20 has the lower output price; Grok 4.20 offers the larger context window. For the 1M input plus 500K output sample, Grok 4.20 is cheaper for the standard workload.

For a 1M input token plus 500K output token workload, the estimated API cost is $6 for Gemini 3.5 Flash and $2.5 for Grok 4.20.

Best Fit

Choose Gemini 3.5 Flash when its provider, model quality, latency, or availability is more important than the numeric price/context winner.

Choose Grok 4.20 when you care most about lower input-token price, lower output-token price, and larger context window.

Decision Notes

On the standard 1M input plus 500K output workload, Grok 4.20 is estimated at $2.5 vs $6 for Gemini 3.5 Flash, saving $3.5 (58.3% lower).
Grok 4.20 is $3.5 cheaper on the standard workload (58.3% lower).
Grok 4.20 is $0.25 cheaper per 1M input tokens (16.7% lower; 1.2x difference).
Grok 4.20 is $6.5 cheaper per 1M output tokens (72.2% lower; 3.6x difference).
Grok 4.20 has 951.42K more context (1.91x larger).

Head-to-Head Specs

Feature	New🔥Gemini 3.5 Flash (Google)	Grok 4.20 (xAI)
Input Price prompt tokens per 1M	$1.5	$1.25
Completion Price per 1M tokens	$9	$2.5
Sample Workload Cost 1M input + 500K output	$6	$2.5
Context Window	1.05M	2M
Release Date	2026-05-19	2026-03-31
Popularity	#11

Use-Case Decision Matrix

Use case	Better pick	Why
Budget-constrained production	Grok 4.20	On the standard 1M input plus 500K output workload, Grok 4.20 is estimated at $2.5 vs $6 for Gemini 3.5 Flash, saving $3.5 (58.3% lower).
High-volume input processing	Grok 4.20	Lower prompt-token price matters most when prompts, retrieved passages, or documents dominate the bill.
Long responses and chatbots	Grok 4.20	Lower output-token price matters most when assistants generate many completion tokens.
RAG or long-document work	Grok 4.20	A larger context window leaves more room for retrieved passages, conversation history, or source files.

Related Alternatives

Same-provider lower-cost swaps

Gemma 4 26B A4B (free) can replace Gemini 3.5 Flash when lower sample workload cost matters most: $0.
Gemma 4 31B (free) can replace Gemini 3.5 Flash when lower sample workload cost matters most: $0.
Lyria 3 Pro Preview can replace Gemini 3.5 Flash when lower sample workload cost matters most: $0.
Lyria 3 Clip Preview can replace Gemini 3.5 Flash when lower sample workload cost matters most: $0.

Larger context near this budget

Llama 4 Scout offers 10M context with $0.23 sample workload cost.

Popular competitors

DeepSeek V4 Flash · DeepSeek · #1
Hy3 preview · Tencent · #2
Claude Opus 4.7 · Anthropic · #3
Claude Sonnet 4.6 · Anthropic · #4

Cheaper alternatives

Review low-cost models sorted by a standard 1M input plus 500K output workload.

Open cheapest models

Larger context alternatives

Find models with larger context windows for RAG, long documents, and codebase review.

Open largest context models

Provider catalogs

Compare models within provider hubs before choosing a final API vendor.

Open provider hubs

Google catalog

Review all tracked Google models before deciding whether this matchup is the right shortlist.

Open Google models

xAI catalog

Check other xAI models with comparable pricing, context, or release timing.

Open xAI models

Gemini 3.5 Flash

Gemini 3.5 Flash is Google's high-efficiency multimodal model, bringing near-Pro level coding and reasoning at Flash-tier cost and speed. It is highly optimized for coding proficiency and parallel agentic execution...

Grok 4.20

Grok 4.20 is a reasoning model from xAI with industry-leading speed and agentic tool calling capabilities. It combines the lowest hallucination rate on the market with strict prompt adherance, delivering...