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Cost and performance comparison

Grok 4.5 vs Gemini 3.1 Pro

Model AxAI

Grok 4.5

Capability score (editorial)90/100
Cost / 1M Tokens
$3.20
70% in · 30% out mix
Value Index (score÷cost)
28.1
Higher = better value
Speed
89/100
Context
500K
Tier
Smart Tier

List price from the xAI pricing page, verified October 12, 2026.

Check the source

How we verify prices

Model BGoogle

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 12, 2026.

Check the source

How we verify prices

In-depth analysis

Grok 4.5 vs Gemini 3.1 Pro: Detailed Comparison

Grok 4.5 is xAI's mid-range-tier language model with a 500K-token context window, excelling at reasoning. Gemini 3.1 Pro from Google is a mid-range-tier model supporting 1.0M tokens in context, with standout performance in vision/multimodal.

Grok 4.5 is both the cheaper and the stronger model here — for the same text it costs 34% less than Gemini 3.1 Pro and still leads on combined coding and reasoning by 2 points. There is no tradeoff to weigh on this pair: unless you need something specific from Gemini 3.1 Pro, the cheaper model is simply the better one. Grok 4.5 is priced at $2.00/M input tokens and $6.00/M output tokens. Gemini 3.1 Pro costs $2.00/M input and $12.00/M output.

On iOPTERA's editorial scores, Grok 4.5 leads with 89/100 for coding and 90/100 for reasoning, against Gemini 3.1 Pro's 88/100 and 89/100.

Capability breakdown

Across the five core benchmark categories, here is how Grok 4.5 and Gemini 3.1 Pro stack up head to head:

coding
89
88
reasoning
90
89
data extraction
88
90
creative tasks
89
88
vision/multimodal
86
95

Best model by task

  • coding: Grok 4.5 wins with 89/100
  • reasoning: Grok 4.5 wins with 90/100
  • data extraction: Gemini 3.1 Pro wins with 90/100
  • creative tasks: Grok 4.5 wins with 89/100
  • vision/multimodal: Gemini 3.1 Pro wins with 95/100

Estimated monthly cost at scale

For 10M + 2M tokens of text a month (counted the way OpenAI's tokenizer counts), Grok 4.5 runs about $32.00 while Gemini 3.1 Pro runs about $42.68 — Grok 4.5 saves roughly $10.68 (25%) every month.

What actually decides it

Grok 4.5 and Gemini 3.1 Pro 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.

Grok 4.5 and Gemini 3.1 Pro were released within 5 months of each other, so they are competing on the same evaluations under roughly the same conditions. That makes a direct benchmark comparison meaningful here in a way it usually is not — neither model has the advantage of being measured on a newer, easier set of tests.

Gemini 3.1 Pro carries the larger context window at 1.0M tokens versus 500K for Grok 4.5. The gap is real but not decisive — it matters if your prompts routinely run long, and is irrelevant if they sit where most production prompts sit, well under 100K. Bear in mind that filling a large window is also what makes a request expensive.

Throughput is close enough to ignore — 89/100 versus 82/100. Neither model will feel noticeably quicker in an interactive product, so latency is not a reason to choose between them.

One practical asymmetry: Gemini 3.1 Pro offers a batch API at 50% off standard rates, and Grok 4.5 does not. For anything that does not need an answer immediately — nightly enrichment, backfills, evaluation runs — that discount can be worth more than the difference in list price, and it is easy to overlook when comparing headline rates.

Grok 4.5 wins this comparison outright — cheaper and stronger. Choose Gemini 3.1 Pro only if it has a specific capability you need; on price and benchmarks it is behind on both.

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 termGrok 4.5Gemini 3.1 Pro
List price (input / output)$2.00 / $6.00$2.00 / $12.00
Cached input$0.3015% of the input price$0.2010% of the input price
Batch APINot on the price page50% off input and output
Long promptsFrom 200K tokens: $4.00 / $12.00Over 200K tokens: $4.00 / $18.00
Input with 80% cache hits$0.64$0.56

With 80% of input served from the cache, Gemini 3.1 Pro costs 15% less than Grok 4.5 for the same input text, counting each model's tokenizer.The tokenizer factor for Grok 4.5, 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 xAI, Google.

Capability scores

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

CategoryGrok 4.5Gemini 3.1Winner

Coding

89
88
A

Reasoning

90
89
A

Extraction

88
90
B

Creative

89
88
A

Vision

86
95
B
Grok 4.5: 3 wins
Gemini 3.1 Pro: 2 wins
Grok 4.5 leads overall

Speed Score

89/100vs82/100
GrokGemini

Context Window

500Kvs1049K
GrokGemini

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
Grok 4.5
$0.80
Gemini 3.1 Pro
$0.78

Business email

One typical email (~200 words)

~270 tokens
Grok 4.5
$54.00
Gemini 3.1 Pro
$52.38

Code file

50-line Python script

~400 tokens
Grok 4.5
$80.00
Gemini 3.1 Pro
$77.60

Prices shown are for 100,000 runs of each workload — one run costs a fraction of a cent on both Grok 4.5 and Gemini 3.1 Pro, 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

30M tokens
Prompt 70%Completion 30%
Cheaper

Grok 4.5

$96.00/mo

$1,152.00/yr

$2.00/M input$6.00/M output

Gemini 3.1 Pro

$145.50/mo

$1,746.00/yr

$2.00/M input$12.00/M output

Annual Savings

$594.00 saved per year

Grok 4.5 cheaper · $49.50/mo

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