API cost decision in 10 seconds

Gemini 3.1 Pro Preview Custom Tools vs GPT-5.3-Codex

Pick Gemini 3.1 Pro Preview Custom Tools when budget and context both matter.

Page updated: 2026-05-26T10:03:26Z Data confirmed: 2026-05-26T12:38:15Z Prices normalized to USD per 1M tokens Sample workload: 1M input + 500K output

Budget verdict

Pick Gemini 3.1 Pro Preview Custom Tools when budget and context both matter.

On the standard 1M input plus 500K output workload, Gemini 3.1 Pro Preview Custom Tools is estimated at $8 vs $8.75 for GPT-5.3-Codex, saving $0.75 (8.6% lower).

Cost-first pickGemini 3.1 Pro Preview Custom Tools

Context-first pickGemini 3.1 Pro Preview Custom Tools

Sample savings$0.758.6%

10x traffic gap$7.5

Gemini 3.1 Pro Preview Custom Tools is cheaper on the standard workload and also has the larger context window. At 10x that traffic, the same price gap is about $7.5. Use the calculator below to replace the sample workload with your own token volume.

Cost sensitivity

Workload Sensitivity

Same prices, different token mixes.

Cost winner changes by workload shape: input-heavy / RAG favors GPT-5.3-Codex, balanced workload favors Gemini 3.1 Pro Preview Custom Tools, and output-heavy chatbot favors Gemini 3.1 Pro Preview Custom Tools.

Workload shape	Token mix	Better pick	Gemini 3.1 Pro Preview Custom Tools	GPT-5.3-Codex
Input-heavy / RAG	5M input + 500K output	GPT-5.3-Codex	$16	$15.75
Balanced workload	1M input + 1M output	Gemini 3.1 Pro Preview Custom Tools	$14	$15.75
Output-heavy chatbot	1M input + 5M output	Gemini 3.1 Pro Preview Custom Tools	$62	$71.75

Cheaper input GPT-5.3-Codex $2 vs $1.75 / 1M

GPT-5.3-Codex is $0.25 cheaper per 1M input tokens (12.5% lower; 1.14x difference).

Cheaper output Gemini 3.1 Pro Preview Custom Tools $12 vs $14 / 1M

Gemini 3.1 Pro Preview Custom Tools is $2 cheaper per 1M output tokens (14.3% lower; 1.17x difference).

Larger context Gemini 3.1 Pro Preview Custom Tools 1.05M vs 400K

Gemini 3.1 Pro Preview Custom Tools has 648.76K more context (2.62x larger).

Sample workload Gemini 3.1 Pro Preview Custom Tools $8 vs $8.75

Gemini 3.1 Pro Preview Custom Tools is $0.75 cheaper on the standard workload (8.6% lower).

Estimate your workload cost

Your Workload Cost

Prices are normalized to USD per 1M tokens.

Monthly input tokens Monthly output tokens

Gemini 3.1 Pro Preview Custom Tools Calculating… Estimated API cost

GPT-5.3-Codex 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

GPT-5.3-Codex has the lower input price; Gemini 3.1 Pro Preview Custom Tools has the lower output price; Gemini 3.1 Pro Preview Custom Tools offers the larger context window. For the 1M input plus 500K output sample, Gemini 3.1 Pro Preview Custom Tools is cheaper for the standard workload.

For a 1M input token plus 500K output token workload, the estimated API cost is $8 for Gemini 3.1 Pro Preview Custom Tools and $8.75 for GPT-5.3-Codex.

Best Fit

Choose Gemini 3.1 Pro Preview Custom Tools when you care most about lower output-token price, and larger context window.

Choose GPT-5.3-Codex when you care most about lower input-token price.

Decision Notes

On the standard 1M input plus 500K output workload, Gemini 3.1 Pro Preview Custom Tools is estimated at $8 vs $8.75 for GPT-5.3-Codex, saving $0.75 (8.6% lower).
Gemini 3.1 Pro Preview Custom Tools is $0.75 cheaper on the standard workload (8.6% lower).
GPT-5.3-Codex is $0.25 cheaper per 1M input tokens (12.5% lower; 1.14x difference).
Gemini 3.1 Pro Preview Custom Tools is $2 cheaper per 1M output tokens (14.3% lower; 1.17x difference).
Gemini 3.1 Pro Preview Custom Tools has 648.76K more context (2.62x larger).

Head-to-Head Specs

Feature	Gemini 3.1 Pro Preview Custom Tools (Google)	GPT-5.3-Codex (OpenAI)
Input Price prompt tokens per 1M	$2	$1.75
Completion Price per 1M tokens	$12	$14
Sample Workload Cost 1M input + 500K output	$8	$8.75
Context Window	1.05M	400K
Release Date	2026-02-25	2026-02-24

Use-Case Decision Matrix

Use case	Better pick	Why
Budget-constrained production	Gemini 3.1 Pro Preview Custom Tools	On the standard 1M input plus 500K output workload, Gemini 3.1 Pro Preview Custom Tools is estimated at $8 vs $8.75 for GPT-5.3-Codex, saving $0.75 (8.6% lower).
High-volume input processing	GPT-5.3-Codex	Lower prompt-token price matters most when prompts, retrieved passages, or documents dominate the bill.
Long responses and chatbots	Gemini 3.1 Pro Preview Custom Tools	Lower output-token price matters most when assistants generate many completion tokens.
RAG or long-document work	Gemini 3.1 Pro Preview Custom Tools	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 3.1 Pro Preview Custom Tools when lower sample workload cost matters most: $0.
Gemma 4 31B (free) can replace Gemini 3.1 Pro Preview Custom Tools when lower sample workload cost matters most: $0.
Lyria 3 Pro Preview can replace Gemini 3.1 Pro Preview Custom Tools when lower sample workload cost matters most: $0.
Lyria 3 Clip Preview can replace Gemini 3.1 Pro Preview Custom Tools 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.
Grok 4.20 Multi-Agent offers 2M context with $5 sample workload cost.
Grok 4.20 offers 2M context with $2.5 sample workload cost.
GPT-5.4 offers 1.05M context with $10 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

OpenAI catalog

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

Open OpenAI models

Gemini 3.1 Pro Preview Custom Tools

Gemini 3.1 Pro Preview Custom Tools is a variant of Gemini 3.1 Pro that improves tool selection behavior by preventing overuse of a general bash tool when more efficient third-party...

GPT-5.3-Codex

GPT-5.3-Codex is OpenAI’s most advanced agentic coding model, combining the frontier software engineering performance of GPT-5.2-Codex with the broader reasoning and professional knowledge capabilities of GPT-5.2. It achieves state-of-the-art results...