GPT-5.1 Chat vs GPT-5.5
Compare GPT-5.1 Chat and GPT-5.5, both from OpenAI, context windows of 128K vs 1.1M, tested across 52 shared challenges.
Our Verdict
GPT-5.5
GPT-5.1 ChatRunner-up
No community votes yet. On paper, GPT-5.5 has the edge — bigger model tier, newer, bigger context window.
GPT-5.1 Chat is 3.0x cheaper per token — worth considering if cost matters.
Slight edge
API pricing
Cost per 1M tokens
GPT-5.1 Chat
Input
$1.25
4.0× cheaper
Output
$10.00
3.0× cheaper
GPT-5.5
Input
$5.00
Output
$30.00
GPT-5.1 Chat is cheaper on both — 4.0× input, 3.0× output
Writing DNA
Style Comparison
Similarity
51%
GPT-5.5 uses 167.8x more headings
GPT-5.1 Chat
GPT-5.5
73%Vocabulary58%
18wSentence Length18w
0.45Hedging0.74
1.1Bold2.9
2.4Lists5.1
0.00Emoji0.00
0.00Headings1.68
0.06Transitions0.03
Based on 15 + 26 text responses
Research
What we learned reading every model
FAQ
