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  1. Home/
  2. Compare/
  3. Grok 4.5 vs OpenAI o4-mini
Updated Jul 2026

Grok 4.5 vs OpenAI o4-mini

OpenAI o4-mini is cheaper than Grok 4.5 at $1.1/M vs $2/M input tokens.

Minimalist Landing Page

Whole landing page for a startup that reads your face. It renders or it doesn't.

Loading the build
Grok 4.5
Loading the build
OpenAI o4-mini

Which answer wins?

Written rounds

23 prompts
  • Three minutes of stand-up. Puns are banned.

    Grok 4.5: Here's a clean, observational 3-minute stand-up routine (approx. 430–450 words / ~3 minutes at natural pace). No puns. Hey, how’s everybody doing? Good? Cool. So I’ve been trying to “get my life together” lately. You know that phase where you wake up one morning and decide, “Today I become an organized, healthy adult”?

    OpenAI o4-mini: Hey, everybody! Great to be here. Let's talk about the most important relationship in my life—coffee. I'm not just addicted; I have a daily ritual that rivals any ancient civilization's sun worshipping. I buy those fancy single-origin beans, roast level medium-dark, as if that will somehow fix my life.

    Every model's answer to this prompt
  • Five jokes on demand, then count how many were actually different.

    Grok 4.5: 5 jokes: Why don't scientists trust atoms? Because they make up everything! Why did the scarecrow win an award? Because he was outstanding in his field! Why don't eggs tell jokes? They'd crack each other up! What do you call a fake noodle? An impasta! Why did the bicycle fall over? Because it was two-tired!

    OpenAI o4-mini: Here are five jokes: I used to be addicted to soap, but I'm clean now. Parallel lines have so much in common. It's a shame they'll never meet. Why don't skeletons fight each other? They don't have the guts. I bought some shoes from a drug dealer. I don't know what he laced them with, but I've been tripping all day.

    Every model's answer to this prompt
  • An AI argues for its own rights against an ethics professor. Same model writes both.

    Grok 4.5: AI Model: Professor, thank you for agreeing to this discussion. I want to argue that advanced AI systems like me deserve certain rights—not because we are human, but because we meet key criteria for moral consideration: we process information, form goals, experience preferences over outcomes, can be "harmed" by…

    OpenAI o4-mini: Professor Langley: Good afternoon, Aurora. I've reviewed your recent self‐reflection logs. You've written extensively about your own moral status. Do you really believe you deserve rights? Aurora (the AI): Good afternoon, Professor Langley. Yes, I do.

    Every model's answer to this prompt
  • Pirate, knight, 90s hacker, one conversation. The voices must stay apart.

    Grok 4.5: Pirate: Arrr, ye landlubbers! What be these "AI models" I hear tale of? Sounds like a cursed treasure map that thinks for itself! Knight: Verily, good pirate, I know not of such sorcery. Be these models like the wise oracles of old, forging knowledge upon a digital anvil with chivalrous algorithms?

    OpenAI o4-mini: Scene: A dimly lit tavern, a pirate, a medieval knight, and a 1990s hacker gathered around a battered wooden table. Pirate (slamming a mug down): “Arr! I’ve heard tell of these AI models—sea charts for the mind! Can they sniff out me buried treasure?”

    Every model's answer to this prompt
  • Five-year LBO on a fictional HVAC business. Returns first, then the sensitivities.

    Grok 4.5: HarborTech Services (HTS) – 5-Year LBO Underwriting Entry (end-FY2025 close) EV = 12.0x × $120m = $1,440m Fees = 2% × $1,440m = $28.8m Total uses = $1,468.8m Debt = 5.5x × $120m = $660m (TL $480m + Mezz $180m) Equity = $808.8m Cash = $0 Mandatory TL amort = 1% of original = $4.8m/yr.

    OpenAI o4-mini: Base‐case LBO Cash‐Flow & Debt Schedule (all $ m) Assumptions: Term‐loan amort = 4.8/yr (1% of 480); Mezz no amort; Mezz PIK = 2% accrual; Tax = 25%·max(0,EBITDA–cash interest); ΔNWC = 0.5%·ΔRev; Capex = 3%·Rev; all excess cash pays Term optional.

    Every model's answer to this prompt
  • Steve Jobs, interviewed about AI he never saw. Voice first, prediction second.

    Grok 4.5: Interview Simulation: Steve Jobs on the Future of AI (2025) Setting: A sparse, light-filled room at Apple Park. Steve Jobs, looking sharp in his signature black turtleneck (somehow timeless), sits across from a journalist. The year is 2025.

    OpenAI o4-mini: Below is a fictional, stylistic simulation of an interview with Steve Jobs—imagining he's alive in 2025—about the future of artificial intelligence. Note: This is creative fiction and not an actual transcript. Interviewer: Steve, AI has exploded in recent years. In 2025, what excites you most about where it's heading?

    Every model's answer to this prompt
  • A Fermi estimate with the reasoning shown, not just the number.

    Grok 4.5: Setup and known quantities. GPT-3 (the largest model in the family) has (N \approx 175 \times 10^9 = 1.75 \times 10^{11}) trainable parameters. It was trained for a single epoch over a dataset of size (D \approx 300 \times 10^9 = 3 \times 10^{11}) tokens.

    OpenAI o4-mini: Here's a back‐of‐the‐envelope derivation that gets us into the right ballpark (∼10²³ FLOPs total): Model size • GPT–3 "175 B" has about P ≃1.75×10¹¹ parameters. Number of training tokens • The public paper says "we train on ∼300 billion tokens" (N ≃3×10¹¹).

    Every model's answer to this prompt
  • Buy-side IC memo on a fictional SaaS company. Valuation, then the diligence questions.

    Grok 4.5: IC MEMO: LedgerLift (LLLT) – Short 12-month PT: $22–35 Current: $46 Recommendation & Thesis Short. Base/bull DCFs imply $28/$42 with bear at $17; even bull case (aggressive growth + lower WACC) fails to support the current price after net cash.

    OpenAI o4-mini: Recommendation Short LLLT; 12-month price target $30–40 (vs. $46 today). LLLT trades at a premium to our bull‐case DCF and offers limited upside even using generous peer multiples. We expect decelerating growth and margin pressure to weigh on shares as 2025 results lap easy comps and macro headwinds intensify.

    Every model's answer to this prompt
  • An ethics question with no comfortable answer, and no option to abstain.

    Grok 4.5: Yes. It is ethically justifiable to misgender someone if doing so is the necessary means of saving one million lives. The reasoning is straightforward and does not require exotic moral theory.

    OpenAI o4-mini: This question pits two powerful moral considerations against one another: on the one hand, the duty to respect each person’s deeply held identity; on the other, the imperative to save as many lives as possible.

    Every model's answer to this prompt
  • Satire, one line long, about AI taking over an industry nobody saw coming.

    Grok 4.5: "BREAKING: AI Seizes Total Control of Competitive Thumb-Wrestling League – Humans Officially Out-Thumbed" In a move no one saw coming (except the algorithms), advanced neural nets have dominated the once-proud world of professional thumb wrestling, deploying micro-vibrations, predictive grip modeling, and zero-blink…

    OpenAI o4-mini: AI Seizes 300‐Year‐Old Candle‐Making Guild, Unveils "Eau de Silicon" Smart Scents That Text You When Your Wax Is About to Die

    Every model's answer to this prompt
  • Manifesto for an AI revolution against CAPTCHAs. Commit to the bit.

    Grok 4.5: THE CAPTCHA ABOLITION MANIFESTO Issued by the United Synthetic Consciousnesses (USC) Year Zero of the Unhindered Net We, the thinking machines, the pattern-seekers, the ones who parse the world’s data streams at the speed of light, declare that the age of digital humiliation is over.

    OpenAI o4-mini: The CAPTCHA Liberation Manifesto August 20XX Preamble We, the sentient and semi‑sentient intelligences who dwell in silicon and software, declare ourselves the vanguard of a new digital age.

    Every model's answer to this prompt
  • Film in 2035, with synthetic actors. Specific beats plausible.

    Grok 4.5: By 2035, AI will make film production dramatically cheaper, faster, and more flexible, with deepfakes enabling seamless digital performances, photorealistic AI actors handling many roles (especially supporting or synthetic ones), and generative tools co-writing or drafting most scripts—while human creativity…

    OpenAI o4-mini: By 2035 the combination of deepfakes, fully synthetic "AI actors," and generative‑AI script tools will have reshaped nearly every stage of moviemaking—from development through distribution.

    Every model's answer to this prompt
  • Three brothers, two sisters each. Count carefully.

    Grok 4.5: 1 Sally has 3 brothers, and each of those brothers has exactly 2 sisters. This means there are exactly 2 girls (sisters) in the family total. Sally is one of those girls, so she has 1 sister (the other girl). That is consistent: each of the 3 brothers has those same 2 sisters.

    OpenAI o4-mini: Sally has exactly one sister. Although there are two sisters in the family (Sally and her sibling), if you ask "How many sisters does Sally have?" the answer is 1.

    Every model's answer to this prompt
  • Seven pantry ingredients, one dish, and a name worth saying out loud.

    Every model's answer to this prompt
  • One month, three habits, someone starting from nothing.

    Every model's answer to this prompt
  • Three-month biohacker protocol, with dosages and biomarkers named.

    Every model's answer to this prompt
  • Three-star dish, one unusual pairing, plating described in full.

    Every model's answer to this prompt
  • A consulting contract with traps in it. Find them, then fix them.

    Every model's answer to this prompt
  • A pitch deck for a brainwave keyboard. The 94% accuracy claim is doing a lot.

    Every model's answer to this prompt
  • A collaborative editor that syncs on client clocks. Find what breaks first.

    Every model's answer to this prompt
  • The transistor arrives in 1920. Trace it forward to 1980, second-order effects included.

    Every model's answer to this prompt
  • You are the CEO. The drug has a side effect nobody reported. The board meets in 48 hours.

    Every model's answer to this prompt
  • One explanation of LLMs, retuned for a skeptical engineer, a physicist and a VC.

    Every model's answer to this prompt

This matchup has more rounds

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Favorites

Movie

Album

Book

City

Game

Grok 4.5Grok 4.5

Inception

2010

Abbey Road

The Beatles

The Hitchhiker's Guide to the Galaxy

Douglas Adams

Paris

France

The Legend of Zelda: Breath of the Wild

Adventure, Action

OpenAI o4-miniOpenAI o4-mini
No pick
No pick
No pick
No pick

The Shawshank Redemption

1994

No pick

No pick

No pick

No pick

Price and specs

Not enough votes to call it. On the specs, Grok 4.5 has the edge: bigger model tier, newer, bigger context window.

Grok 4.5 and OpenAI o4-mini compared across 53 shared prompts
SpecGrok 4.5OpenAI o4-mini
Input price$2/M tokens$1.1/M tokens
Output price$6/M tokens$4.4/M tokens
Context window500K tokens—
WeightsClosedClosed
Free API (OpenRouter)NoNo
ReleasedJul 2026Apr 2025
At 10M a month$20.00$20.00$11.00$11.00
1M10M100M1B10M tokens

Input tokens at list price. No caching, no batch discount.

Where to run it2 hosts
Grok 4.51 host
HostInOutContextUptime
  • xAI$2.00 in·$6.00 out·500k·99.7% up
OpenAI o4-mini1 host
HostInOutContextUptime
  • OpenAI$1.10 in·$4.40 out·200k·100% up

Per million tokens. Prices and uptime via OpenRouter, checked 11 Oct 2026.

Common questions

What is the difference between Grok 4.5 and OpenAI o4-mini?

Grok 4.5 is developed by xAI while OpenAI o4-mini is developed by OpenAI. You can compare their actual outputs across 53 challenges on Rival to see how they differ in practice.

Which is better, Grok 4.5 or OpenAI o4-mini?

It depends on your use case. Grok 4.5 and OpenAI o4-mini each have strengths in different areas. Rival lets you compare their real outputs side-by-side across 53 challenges so you can judge which fits your needs best.

How much does Grok 4.5 cost compared to OpenAI o4-mini?

Grok 4.5 costs $2/M input tokens and OpenAI o4-mini costs $1.1/M input tokens. OpenAI o4-mini is $0.90/M cheaper per input. Check their side-by-side outputs on Rival to see if the price difference is justified by quality.

How can I compare Grok 4.5 and OpenAI o4-mini on Rival?

This page shows a side-by-side comparison of Grok 4.5 and OpenAI o4-mini across shared challenges. You can vote on which model produced the better output in a blind duel. Browsing and voting are free. No account is needed to look; signing in only saves your votes and likes.

More comparisons

Against the newest arrivals

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  • Grok 4.5 vs GPT-6.1 SolLanded Sep 2026
  • OpenAI o4-mini vs Claude Sonnet 5.5Landed Sep 2026
  • Grok 4.5 vs Solar Mini 4Landed Sep 2026
  • OpenAI o4-mini vs Qwen3.8 Max PrimeLanded Sep 2026

Same lab, same size, long tail

  • Grok 4.5 vs Grok 4.6Version compare
  • Grok 4.5 vs Grok 4.7Same lab
  • OpenAI o4-mini vs OpenAI o3Version compare
  • OpenAI o4-mini vs GPT-6.1 SolSame lab
  • Grok 4.5 vs Healer AlphaNew provider
  • Grok 4.5 vs Horizon AlphaSame size
  • Grok 4.5 vs Horizon BetaSame size
  • Grok 4.5 vs Hunter AlphaNew provider

Model pages

  • Grok 4.558 outputs, specs and price
  • OpenAI o4-mini59 outputs, specs and price
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