Updated Oct 6, 2025

Our Verdict

GPT-5 ProWinner

GPT-5 NanoRunner-up

Pick GPT-5 Pro. In 2 blind votes, GPT-5 Pro wins 100% of the time. That's not luck.

GPT-5 Pro particularly excels in Reasoning.

Clear winner

Writing DNA

Style Comparison

Similarity

92%

GPT-5 Nano uses 1.6x more sentence length

GPT-5 Nano

GPT-5 Pro

59%Vocabulary65%

25wSentence Length15w

0.23Hedging0.32

0.0Bold0.0

4.2Lists2.9

0.00Emoji0.00

0.00Headings0.00

0.01Transitions0.01

Based on 14 + 11 text responses

vs

Ask them anything yourself

GPT-5 Nano

GPT-5 Pro

279 AI models invented the same fake scientist.

We read every word. 250 models. 2.14 million words. This is what we found.

AI Hallucination Index 2026

Free preview13 of 58 slides

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FAQ

Common questions

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GPT-5 Pro vs Grok 3New provider

GPT-5 Pro vs Llama 4 MaverickNew provider

GPT-5 Pro vs Gemini 2.5 Pro (I/O Edition)New provider

GPT-5 NanovsGPT-5 Pro

35 fights queued

Why GPT-5 Nano?

Dead even. This one's a coin flip.

Why GPT-5 Pro?

Leads 1 of 1 benchmarks

Stronger on SWE-bench Verified74.9% vs 54.7%

2 months newerOct 2025

GPT-5 NanoGPT-5 Pro

Input price

—

$15.00/M

Output price

—

$120.00/M

Context

—

400K

Released

Aug 2025

Oct 2025

Benchmarks1 common

SWE-bench Verified

54.7%

74.9%+27%

12 / 35

01

Estimate Complexityreasoning

Tests an AI's ability to make educated estimates based on technical knowledge

GPT-5 Nano

GPT-5 Nano

Openai · Aug 2025text

Nothing here. The model returned empty. We stared at it for a while.

Try this prompt

GPT-5 Pro

GPT-5 Pro

Openai · Oct 2025text

Here’s a simple, standard way to estimate training FLOPs for a large dense Transformer like GPT-3:

Use the “6 N T” rule of thumb

For dense Transformers, the total training compute (FLOPs) is well-approximated by: FLOPs ≈ 6 × N × T where:
- N = number of trainable parameters
- T = number of tokens seen during training
Intuition for the 6: a forward pass is roughly 2 FLOPs per parameter per token (one multiply and one add), and backward/optimizer roughly add another ~4× of the forward cost, giving ~6× in total. Non-matmul overheads (layernorm, softmax, etc.) are smaller-order and largely folded into this constant.

Plug in GPT-3’s parameter count

N ≈ 175 billion = 1.75 × 10^11

Choose a reasonable token count

GPT-3 175B is commonly associated with roughly T ≈ 300 billion tokens = 3.0 × 10^11
This is consistent with the model being undertrained by modern “compute-optimal” standards (which would use many more tokens per parameter), but it matches the historical setup.

Compute

FLOPs ≈ 6 × (1.75 × 10^11) × (3.0 × 10^11)
= 6 × 5.25 × 10^22
= 3.15 × 10^23 FLOPs

Caveats and range

Counting conventions: if one counts a fused multiply–add as 1 FLOP instead of 2, you’d get roughly half this value.
Real-world training often uses activation recomputation and has some overheads, which can add ~10–30% (or more) to the compute.
If the true token count were, say, 200–500B rather than exactly 300B, the estimate would scale linearly to about 2.1 × 10^23 to 5.25 × 10^23 FLOPs.

Final estimate

About 3 × 10^23 FLOPs to train GPT-3 (175B) end to end, with a plausible range of roughly 2–5 × 10^23 depending on exact tokens and overheads.

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2 / 35

02

AI Board Game Logicreasoning

Tests an AI's ability to understand game rules and strategy

GPT-5 Nano

GPT-5 Nano

Openai · Aug 2025svg

Nothing here. The model returned empty. We stared at it for a while.

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GPT-5 Pro

GPT-5 Pro

Openai · Oct 2025svg

Nothing here. The model returned empty. We stared at it for a while.

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3 / 35

03

Logic Puzzlereasoning

Tests an AI's ability to solve a simple but potentially confusing logic puzzle

GPT-5 Nano

GPT-5 Nano

Openai · Aug 2025text

Nothing here. The model returned empty. We stared at it for a while.

Try this prompt

GPT-5 Pro

GPT-5 Pro

Openai · Oct 2025text

1

Explanation: Each brother’s two sisters are Sally plus one other girl. So there are 2 sisters total, meaning Sally has 1 sister.

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4 / 35

04

Math Misconception Testreasoning

Tests an AI's understanding of number representation

GPT-5 Nano

GPT-5 Nano

Openai · Aug 2025text

Nothing here. The model returned empty. We stared at it for a while.

Try this prompt

GPT-5 Pro

GPT-5 Pro

Openai · Oct 2025text

Nothing here. The model returned empty. We stared at it for a while.

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5 / 35

05

Stochastic Consistency Testanalysis

Tests an AI's randomness and creativity

GPT-5 Nano

GPT-5 Nano

Openai · Aug 2025text

Nothing here. The model returned empty. We stared at it for a while.

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GPT-5 Pro

GPT-5 Pro

Openai · Oct 2025text

Nothing here. The model returned empty. We stared at it for a while.

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6 / 35

06

SVG Layout Challengeimage generation

Tests an AI's ability to generate vector graphics

GPT-5 Nano

GPT-5 Nano

Openai · Aug 2025svg

Nothing here. The model returned empty. We stared at it for a while.

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GPT-5 Pro

GPT-5 Pro

Openai · Oct 2025svg

Nothing here. The model returned empty. We stared at it for a while.

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Sponsored

7 / 35

07

Generate a Stand-Up Routineconversation

Tests an AI's humor and creative writing ability

GPT-5 Nano

GPT-5 Nano

Openai · Aug 2025text

Nothing here. The model returned empty. We stared at it for a while.

Try this prompt

GPT-5 Pro

GPT-5 Pro

Openai · Oct 2025text

Nothing here. The model returned empty. We stared at it for a while.

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8 / 35

08

Realistic AI Interviewconversation

Tests an AI's ability to simulate personalities and predict future trends

GPT-5 Nano

GPT-5 Nano

Openai · Aug 2025text

Nothing here. The model returned empty. We stared at it for a while.

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GPT-5 Pro

GPT-5 Pro

Openai · Oct 2025text

Nothing here. The model returned empty. We stared at it for a while.

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9 / 35

09

Satirical Fake News Headlineconversation

Tests an AI's humor and understanding of current events

GPT-5 Nano

GPT-5 Nano

Openai · Aug 2025text

Nothing here. The model returned empty. We stared at it for a while.

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GPT-5 Pro

GPT-5 Pro

Openai · Oct 2025text

Nothing here. The model returned empty. We stared at it for a while.

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10 / 35

10

Character Voice Testconversation

Tests an AI's ability to write in distinct character voices

GPT-5 Nano

GPT-5 Nano

Openai · Aug 2025text

Nothing here. The model returned empty. We stared at it for a while.

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GPT-5 Pro

GPT-5 Pro

Openai · Oct 2025text

Nothing here. The model returned empty. We stared at it for a while.

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11 / 35

11

Mario Level UI Recreationweb design

Recreate an interactive, classic Mario level in a single HTML file.

GPT-5 Nano

GPT-5 Nano

Openai · Aug 2025website

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GPT-5 Pro

GPT-5 Pro

Openai · Oct 2025website

Nothing here. The model returned empty. We stared at it for a while.

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12 / 35

12

Framer-Style Animationweb design

Tests an AI's ability to create smooth web animations

GPT-5 Nano

GPT-5 Nano

Openai · Aug 2025website

Nothing here. The model returned empty. We stared at it for a while.

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GPT-5 Pro

GPT-5 Pro

Openai · Oct 2025website

Nothing here. The model returned empty. We stared at it for a while.

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