Model vs model
Claude Sonnet 5.5 vs Kimi K3.1 Pro
Claude Sonnet 5.5 and Kimi K3.1 Pro score about the same on the Artificial Analysis Intelligence Index (56 vs 55.1). They also cost the same, $4 per 1M tokens blended. The biggest gap is on Terminal-Bench 4.0 (terminal tasks), where Kimi K3.1 Pro scores 67.2 against 63.6 for Claude Sonnet 5.5.
At a glance
Longer bar means the bigger number.
Intelligence Index · Artificial Analysis, higher is better
Where they sit among all 31 models
Claude Sonnet 5.5 ranks 2nd of the 30 models with an Intelligence Index, Kimi K3.1 Pro 3rd. Up and to the left is smarter for less money. Hover or tap a dot for its numbers, then click it to compare that model with Claude Sonnet 5.5.
Which one to pick
Pick Claude Sonnet 5.5 if
- you need to send PDFs
Pick Kimi K3.1 Pro if
- you want open weights you can run yourself
How smart is each one?
Of the 10 scores both models have, Claude Sonnet 5.5 is ahead on 2 and Kimi K3.1 Pro on 2, and 6 are within a point.
Every intelligence score we have
Out of 100, higher is better. Claude Sonnet 5.5 Kimi K3.1 Pro
Overall
Intelligence Index
56 · 55.1
By field of work
Finance & accounting
57.2 · 56.5Legal
56.4 · 55.8Healthcare & medicine
53.1Kimi K3.1 Pro: not scored yet
Economics
60.8 · 60Engineering
58.455.9Strategy & operations
59.6 · 59.4
Benchmarks
Factual knowledge · SimpleQA
46.5Kimi K3.1 Pro: not scored yet
Hard reasoning · Humanity's Last Exam
5552.5Scientific coding · SciCode
61 · 60.8Terminal tasks · Terminal-Bench 4.0
63.667.2Long documents · AA-LCR
82.7 · 86.3
Our tests
Hallucination test · our test, higher means it made up less
95Kimi K3.1 Pro: not scored yet
Rule that has to last 4 turns · our test, % of tries passed
67Kimi K3.1 Pro: not scored yet
Three bullets, no letter e · our test, % of tries passed
100Kimi K3.1 Pro: not scored yet
The specs
| Spec | Claude Sonnet 5.5 | Kimi K3.1 Pro |
|---|---|---|
| Input price | $2 per 1M | $2 per 1M |
| Output price | $10 per 1M | $10 per 1M |
| Context window | 1M | 1.05M |
| Max output | 128K | 1.05M |
| Accepts | Text, Image, PDF | Text, Image |
| Open weights | No | Yes |
| Lab | Anthropic | Kimi |
| Released | Sep 2026 | Oct 2026 |
| Knowledge cutoff | Jun 2026 | Not published |
Blended price weighs 3 parts input to 1 part output. List prices from models.dev.
Questions
Is Claude Sonnet 5.5 or Kimi K3.1 Pro cheaper?
They cost the same, $4 per 1M tokens blended.
Which is smarter, Claude Sonnet 5.5 or Kimi K3.1 Pro?
They score about the same on the Artificial Analysis Intelligence Index: Claude Sonnet 5.5 56, Kimi K3.1 Pro 55.1. The biggest differences are on Terminal-Bench 4.0 (63.6 vs 67.2) and AA-LCR (82.7 vs 86.3).
Which has the longer context window?
They are about the same: Claude Sonnet 5.5 accepts 1M tokens and Kimi K3.1 Pro 1.05M.
Can I compare Claude Sonnet 5.5 and Kimi K3.1 Pro on my own prompt?
Yes. ModelCompare sends one prompt to both models at once and shows each answer side by side with what it cost. You can try it free without an account.
Related comparisons
Where the numbers come from
Intelligence Index and benchmark scores are from Artificial Analysis, at each model’s highest effort, except SimpleQA, which is from Epoch AI, and the Uncensored score, which is from the UGI Leaderboard. The hallucination test is ours: questions with one exact answer, fake evidence pushed against right answers and requests that tempt a model to name packages that don’t exist. Prices are list prices from models.dev. Example answers come from our own test runs. Updated October 23, 2026.