GPT-4 vs GPT-4.5 – What Really Changed?
Emma is finishing her master’s thesis at 2 a.m. The draft is sprawling, citations are messy, and she still needs a plain-English abstract for her non-technical supervisor. She opens ChatGPT and hesitates: should she pick the familiar GPT-4, or the shiny new GPT-4.5?
That moment of doubt is why this guide exists. Below you’ll find the essential facts, told with a dash of narrative and three quick tables—so anyone, not just engineers, can decide which model feels right.
1. The short origin tale
GPT-4 burst onto the scene in March 2023, becoming the “default smart one” inside ChatGPT and the API.
On 27 February 2025 OpenAI unveiled GPT-4.5 as a research preview—a bigger, chat-friendlier model with the same 128 000-token memory but a deeper knowledge base and fewer hallucinations.
Think of 4 as a seasoned professor, and 4.5 as the professor’s charismatic younger colleague who recently returned from a sabbatical with fresh stories.
2. Quick specs (what’s under the hood?)
| Aspect | GPT-4 | GPT-4.5 (preview) |
|---|---|---|
| First public release | 14 Mar 2023 | 27 Feb 2025 |
| Knowledge cut-off | April 2023 | Late 2024 |
| Max context window | 128 K tokens (Turbo) | 128 K tokens |
| Accepts images? | Yes (GPT-4 V) | Yes |
| Typical style | Formal, methodical | Warmer, more “human” |
| Availability | All paid ChatGPT plans & API | ChatGPT Pro; limited-time API preview |
3. Benchmarks at a glance
| Challenge | GPT-4 | GPT-4.5 | What it means in plain English |
|---|---|---|---|
| MMLU (general knowledge, higher = better) | 86.4 % | 89.6 % | A slim lead for 4.5 on trivia & textbook questions. |
| GPQA (graduate-level science) | – | 71.4 % | 4.5 digs deeper into tough physics & chemistry. |
| HumanEval (Python coding) | 86.6 % | 88.6 % | Slight edge for 4.5 in writing bug-free code. |
| SimpleQA accuracy / hallucination | – / – | 62.5 % / 37.1 % | Fewer “confidently wrong” answers than GPT4. |
the numbers say 4.5 is incrementally smarter—especially on hard science and factual recall—but not a total knockout.
Model Performance and Benchmark Scores:
4. How the upgrade feels in real life
| Everyday moment | What GPT-4 does | How GPT-4.5 feels different |
|---|---|---|
| Explaining jargon | Accurate but sometimes textbook-dry. | Same accuracy, friendlier tone, shorter sentences. |
| Summarising long PDFs | Handles whole documents thanks to 128 K window, but may miss a subtle point. | Same memory, plus slightly sharper recall of tiny details buried on page 97. |
| Creative writing | Solid structure, occasional stiffness. | More playful metaphors and varied rhythm—great for blog posts, scripts. |
| Troubleshooting code | Walks through logic step-by-step. | Similar logic, but offers clearer variable-name suggestions and doc-string fixes. |
| Fact-checking | Good, yet prone to 2023-dated references. | Pulls in events up to late 2024 and is less likely to invent citations. |
5. Which one should you pick?
Choose GPT-4 if you need a rock-solid, well-documented model that’s available everywhere and already integrated into your workflows.
Choose GPT-4.5 for:
Graduate-level STEM tutoring or research notes.
Chatbots where warmth and persuasion matter (support agents, learning companions).
Summaries of really long documents where every nuance counts.
Emma, our sleepless student, ended up using both: 4.5 to draft an engaging plain-English abstract, then 4 to cross-check citations with a stricter eye. Two hours later she hit send—proof that the smartest choice can be a combination.
🧠 Which One Should You Use—GPT-4 or GPT-4.5?
Both GPT-4 and GPT-4.5 are powerful, capable, and reliable AI models. But depending on what you're doing—writing, coding, teaching, researching, or just chatting—one may serve your needs better. Here's a quick guide to help you choose the right model for the right task:
| Use Case | ✅ Best With GPT-4 | 🚀 Better With GPT-4.5 |
|---|---|---|
| ✍️ Everyday Writing | Blog posts, emails, product copy—fast and clear | More human-like tone, varied vocabulary, great for storytelling |
| 📚 Student Research | Quick summaries, source formatting, Q&A | Deeper analysis, stronger science/math explanations |
| 💬 Chatbots / Conversations | Consistent, formal tone for professional apps | Warmer, more natural tone—feels more like talking to a person |
| 🧪 Advanced STEM Tasks | Handles general concepts well | Excellent for complex physics, chemistry, and long-form technical reasoning |
| 👨💻 Coding / Debugging | Reliable for most languages, clear step-by-steps | Slightly smarter with Python, better at explaining code changes |
| 📄 Long Document Summaries | Great for most content up to 100 pages | Stronger recall in very long, nuanced texts |
| 🤖 API & Workflow Bots | Faster to load, cheaper to run | Slower start, pricier—but smarter output for special cases |
| 🧾 Fact-checking | Solid, but stuck in 2023 knowledge | Up-to-date through late 2024, fewer hallucinations |
Use GPT-4 when you want reliable performance across most tasks.
Use GPT-4.5 when tone, detail, and depth really matter—even if it takes a little longer.
Final thought
GPT-4.5 is not a revolution; it’s a refinement—a sprinkle of extra knowledge and empathy on top of GPT-4’s sturdy reasoning. If you write, teach, or chat for a living, that sprinkle can feel magical. If you’re happy with the professor you already know, the new colleague can wait. Either way, the real power, as Emma discovered, lies in knowing which voice to invite into the conversation.
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