Gemini 3.5 Flash vs GPT-5.1-Codex-Mini, API pricing and model comparison

Compare Gemini 3.5 Flash vs GPT-5.1-Codex-Mini side by side by input/output token price, context window, benchmark signals, capabilities, and example monthly API cost.

Quick comparison summary

This page compares Gemini 3.5 Flash vs GPT-5.1-Codex-Mini in one matrix. Current records: Gemini 3.5 Flash on OpenRouter: $1.5/$9 per 1M tokens, 1049K context window; GPT-5.1-Codex-Mini on OpenRouter: $0.25/$2 per 1M tokens, 400K context window. Prices are estimates—verify official provider pages before production use.

Gemini 3.5 Flash

google/gemini-3.5-flash

OpenRouter

Input: $1.50 / 1M
Output: $9.00 / 1M
Context: 1.0m
Model page: Details

GPT-5.1-Codex-Mini

openai/gpt-5.1-codex-mini

OpenRouter

Input: $0.2500 / 1M
Output: $2.00 / 1M
Context: 400k
Model page: Details

Comparison matrixLLM Table

Models to compare2/4

Model 1

1.0M

Select model344 models

Model 2

400K

Select model344 models

Google: Gemini 3.5 Flash

OpenRouter

Input

$1.50 / 1M

Output

$9.00 / 1M

Context

1.0MLargest context

Monthly cost

$420.00

Benchmark

—

VisionToolsJSONReasoningAudioLong context

OpenAI: GPT-5.1-Codex-Mini

OpenRouter

Cheapest (this scenario)

Input

$0.2500 / 1M

Output

$2.00 / 1M

Context

400K

Monthly cost

$85.00

Benchmark

1,240Top benchmarkLMArena WebDev Arena

VisionToolsJSONReasoningLong context

Google: Gemini 3.5 Flash

OpenRouter

OpenAI: GPT-5.1-Codex-Mini

OpenRouter

Input

$1.50 / 1M

$0.2500 / 1MCheapest (this scenario)

Output

$9.00 / 1M

$2.00 / 1MCheapest (this scenario)

Context

1.0MLargest context

400K

Benchmark

—

1,240Top benchmark

LMArena WebDev Arena

Monthly cost

$420.00

$85.00Cheapest (this scenario)

Capabilities

VisionToolsJSONReasoningAudioLong context

VisionToolsJSONReasoningLong context

FAQ

Model comparison notes

How do Gemini 3.5 Flash vs GPT-5.1-Codex-Mini API prices compare?

Compare input and output prices per 1M tokens side by side. The same underlying model can list different prices by route (Direct API vs OpenRouter); this table uses the selected route records.

Which model looks cheaper?

Scenario cost depends on your input/output mix. The example monthly cost in the table uses default token volumes—adjust with the cost calculator for your traffic.

Are benchmark scores included?

Independent or provider-reported benchmark signals appear when available. Benchmarks do not replace price analysis—evaluate both for your quality requirements.

Related comparisons

Anthropic Anthropic Claude 3 5 Haiku Openrouter vs Openai Openai GPT 5 1 Codex Mini Openrouter Anthropic Anthropic Claude 3 Haiku Openrouter vs Openai Openai GPT 5 1 Codex Mini Openrouter Anthropic Anthropic Claude Haiku 4 5 Openrouter vs Google Google Gemini 3 5 Flash Openrouter Anthropic Anthropic Claude Haiku 4 5 Openrouter vs Openai Openai GPT 5 1 Codex Mini Openrouter Anthropic Anthropic Claude Haiku Latest Openrouter vs Openai Openai GPT 5 1 Codex Mini Openrouter Anthropic Anthropic Claude Opus 4 1 Openrouter vs Google Google Gemini 3 5 Flash Openrouter Anthropic Anthropic Claude Opus 4 1 Openrouter vs Openai Openai GPT 5 1 Codex Mini Openrouter Anthropic Anthropic Claude Opus 4 5 Openrouter vs Google Google Gemini 3 5 Flash Openrouter

Popular comparisons

Open high-intent model matchups directly with ready-made links.