Which is more cost-effective, Gemini 3.1 Pro or GPT-4o?

Based on 1M input + 1M output tokens, Gemini 3.1 Pro costs $14.00/month versus GPT-4o at $12.50/month. The cheaper option depends on your token volume and prompt-to-completion ratio. Use the interactive calculator on this page to enter your exact usage.

How accurate is this cost comparison?

List prices come from each provider's own pricing page and every model page shows when they were last verified. The capability scores are iOPTERA's editorial composites — informed by public benchmarks, not benchmark results themselves; the methodology page explains how they are set.

Which model scores higher on benchmarks?

Gemini 3.1 Pro scores 88 in coding and 89 in reasoning benchmarks. GPT-4o scores 87 in coding and 90 in reasoning. See the full 5-category breakdown in the Benchmark Comparison section above.

What are the context window sizes of Gemini 3.1 Pro and GPT-4o?

Gemini 3.1 Pro supports a 1.0M-token context window while GPT-4o supports 128K tokens. A larger context window lets you process more text in a single API call.

Which model is faster for real-time applications?

Gemini 3.1 Pro has a speed score of 82/100 and GPT-4o scores 90/100 on our latency benchmark. For interactive chatbots and low-latency tasks, the higher speed score is preferable.

Can I calculate costs for my specific token volume?

Yes. Use the interactive cost calculator on this page. Enter your monthly token volume and adjust the prompt-to-completion ratio. You can also use presets for common scenarios like Customer Support Bots (~30M tokens/month) or Document Summarizers (~15M tokens/month).

Cost and performance comparison

Gemini 3.1 Pro vs GPT-4o

Model AGoogle

Gemini 3.1 Pro

Capability score (editorial)89/100

Cost / 1M Tokens: $5.00; 70% in · 30% out mix
Value Index (score÷cost): 18.4; Higher = better value

Speed: 82/100
Context: 1.0M
Tier: Smart Tier

List price from the Google pricing page, verified October 19, 2026.

Check the source

How we verify prices

Model BOpenAI

GPT-4o

Capability score (editorial)90/100

Cost / 1M Tokens: $4.75; 70% in · 30% out mix
Value Index (score÷cost): 18.9; Higher = better value

Speed: 90/100
Context: 128K
Tier: Smart Tier

List price from the OpenAI pricing page, verified September 30, 2026.

Check the source

How we verify prices

In-depth analysis

Gemini 3.1 Pro vs GPT-4o: Detailed Comparison

Gemini 3.1 Pro is Google's mid-range-tier language model with a 1.0M-token context window, excelling at vision/multimodal. GPT-4o from OpenAI is a mid-range-tier model supporting 128K tokens in context, with standout performance in vision/multimodal.

Price is not the deciding factor here. For the same text, GPT-4o and Gemini 3.1 Pro land within 2% of each other, which is inside the margin your own input/output ratio will move anyway. Pick on capability, context, or latency instead — the monthly bill will look much the same either way. Gemini 3.1 Pro is priced at $2.00/M input tokens and $12.00/M output tokens. GPT-4o costs $2.50/M input and $10.00/M output.

On iOPTERA's editorial scores, Gemini 3.1 Pro leads with 88/100 for coding and 89/100 for reasoning, against GPT-4o's 87/100 and 90/100.

Capability breakdown

Across the five core benchmark categories, here is how Gemini 3.1 Pro and GPT-4o stack up head to head:

coding

Gemini 3.1 leads

reasoning

GPT-4o leads

data extraction

GPT-4o leads

creative tasks

GPT-4o leads

vision/multimodal

Tie

Best model by task

coding: Gemini 3.1 Pro wins with 88/100
reasoning: GPT-4o wins with 90/100
data extraction: GPT-4o wins with 92/100
creative tasks: GPT-4o wins with 92/100

Estimated monthly cost at scale

For 10M + 2M tokens of text a month (counted the way OpenAI's tokenizer counts), Gemini 3.1 Pro runs about $42.68 while GPT-4o runs about $45.00 — Gemini 3.1 Pro saves roughly $2.32 (5%) every month.

What actually decides it

Gemini 3.1 Pro and GPT-4o come from different labs, which means different tokenizers, different API shapes, and a second vendor relationship. The same English text does not produce the same token count on both, so a price-per-million comparison understates the difference — measure your own prompts on each before treating the headline rates as the full story.

Gemini 3.1 Pro and GPT-4o are 21 months apart, which is more than one generation in this market. Benchmark comparisons across that gap flatter the older model: it was measured against the evaluations that existed at the time. Treat GPT-4o's scores as a floor for what it does well and be sceptical of a close-looking result.

The context gap is the largest single difference on this pair: Gemini 3.1 Pro takes 1.0M tokens against 128K for GPT-4o, roughly 8.2x. That is the difference between feeding in a whole repository or a full contract set and having to chunk it. If your work involves documents you cannot split cleanly, this decides it on its own.

Throughput is close enough to ignore — 90/100 versus 82/100. Neither model will feel noticeably quicker in an interactive product, so latency is not a reason to choose between them.

With prices this close (2% apart), pick on fit rather than cost. Gemini 3.1 Pro holds the benchmark edge; weigh that against where each one is weakest — coding and coding respectively — and use the calculator above with your own token mix.

What you actually pay

The list price is only the start. Prompt caching, batch processing and long prompts change the bill, and each provider sets them differently. Prices per 1M tokens.

Pricing terms beyond the list price, per 1M tokens
Pricing term	Gemini 3.1 Pro	GPT-4o
List price (input / output)	$2.00 / $12.00	$2.50 / $10.00
Cached input	$0.2010% of the input price	$1.2550% of the input price
Batch API	50% off input and output	50% off input and output
Long prompts	Over 200K tokens: $4.00 / $18.00	—
Input with 80% cache hits	$0.56	$1.50

With 80% of input served from the cache, Gemini 3.1 Pro costs 64% less than GPT-4o for the same input text, counting each model's tokenizer.The tokenizer factor for Gemini 3.1 Pro is our estimate until it is measured.

The last row assumes 80% of input tokens are read from the cache, as in a chat app that re-sends a long system prompt or RAG over the same documents. Cache-write and storage charges are not included.

Gemini also bills cache storage by the hour.

Checked on October 8, 2026 against the pricing pages of Google, OpenAI.

Capability scores

iOPTERA editorial scores across 5 categories — informed by public benchmarks, not measured by us

CategoryGemini 3.1GPT-4oWinner

Coding

Reasoning

Extraction

Creative

Vision

Tied

Gemini 3.1 Pro: 1 wins

GPT-4o: 3 wins

GPT-4o leads overall

Speed Score

82/100vs90/100

GeminiGPT-4o

Context Window

1049Kvs128K

GeminiGPT-4o

What Is a Token?

Models don't read words — they process tokens.

A token is roughly 4 characters of English text (~¾ of a word). Your API bill is priced per million tokens — understanding this directly reduces your costs.

Short phrase

"Hello, world!"

4 tokens

Gemini 3.1 Pro: $0.78
GPT-4o: $1.00

Business email

One typical email (~200 words)

~270 tokens

Gemini 3.1 Pro: $52.38
GPT-4o: $67.50

Code file

50-line Python script

~400 tokens

Gemini 3.1 Pro: $77.60
GPT-4o: $100.00

Prices shown are for 100,000 runs of each workload — one run costs a fraction of a cent on both Gemini 3.1 Pro and GPT-4o, so the number only becomes meaningful at production volume. Input tokens only; add your output volume in the calculator below.

How to check your token usage

response.usage.total_tokens

Every API response includes a usage object. Sum total_tokens across all calls to get your monthly figure, then use the calculator below.

Your Cost Calculator

Enter your actual monthly token usage to see real savings

Quick Presets

Monthly Token Volume

30M tokens

Prompt / Completion Split

Prompt 70%Completion 30%

Gemini 3.1 Pro

$145.50/mo

$1,746.00/yr

$2.00/M input$12.00/M output

Cheaper

GPT-4o

$142.50/mo

$1,710.00/yr

$2.50/M input$10.00/M output

Annual Savings

$36.00 saved per year

GPT-4o cheaper · $3.00/mo

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