Why the Same Prompt Gives Different Answers in ChatGPT and Claude
Same prompt, different results across ChatGPT, Claude and Gemini, or even twice in the same chat. Here's why, and how to get consistent answers.
PromptItIn team
5 min read · Updated
Short answer
Different AI models are trained differently and have different default styles, so the same prompt lands differently. Even one model varies run to run because answers are sampled. To get consistent results, spell out the format, length and tone, give an example, and tune the prompt a little for each model.
You pasted the same prompt into ChatGPT and Claude and got two different answers. Then you asked ChatGPT again and got a third. This is normal, and you can narrow the spread a lot.
Each model has its own defaults
Models are trained on different data with different goals, so their defaults differ: how long they write, how formal they sound, whether they use headings or lists.
Whatever your prompt doesn't specify, each model fills in its own way.
Answers are sampled, not looked up
A model picks each next word from likely options, with some randomness. Ask twice and you can get two valid but different answers. That's useful for ideas and frustrating for consistency.
Hidden context differs
Chat apps add their own instructions, and your memory or custom instructions can change answers too. Two people with the same prompt may not be sending the same thing.
How to get consistent answers
Decide what the model would otherwise decide: length, format, tone and structure. Add one example of a good answer. The more you specify, the more alike the results across models and runs.
Prompt
Summarize the article below for a busy manager.
Format:
- One sentence: the main point
- Three bullets: key facts, each under 15 words
- One line: what to do next
Tone: plain and neutral. No headings.
Article:
[PASTE ARTICLE]
Tune lightly for each model
Claude tends to follow explicit structure closely. ChatGPT responds well to a clear role and examples. Gemini benefits from stating the format and sources you want. Small adjustments beat one prompt for everything.
Practical tips
Specify length, format and tone every time it matters.
Add one example of the answer you want.
Ask for several versions when you want variety; pin the format when you want consistency.
Check memory and custom instructions if results surprise you.
Frequently asked questions
Why does ChatGPT give a different answer every time?
Answers are sampled with some randomness, so each run can differ. Pinning down the format, length and tone, and adding an example, makes results much more consistent.
Is Claude or ChatGPT better for the same prompt?
It depends on the task. Compare them on your own prompt, but first specify the format and length so you're comparing the thinking, not the default style.
Get a prompt tuned for the AI you're using
PromptItIn asks what's missing, then writes a clear prompt for ChatGPT, Claude or Gemini. Free to start.
