Skip to main content
BenchLM
Advertise

Model comparison

Claude Sonnet 4.5 vs Kimi K2

Data verified

Head-to-head evidence from 3 shared benchmark results across 2 categories. Overall scores shown here use the public BenchAlign v5 ranking lane.

53.61/100
Margin
26.4pts
← winning
Kimi K2
Moonshot AI
27.19/100
0 category wins1 category wins

Public leaderboard positions: Claude Sonnet 4.5 #96 (Estimated); Kimi K2 #189 (Supported). Intervals and evidence labels describe ranking uncertainty, not a guarantee for a specific workload.

Evidence parity. Claude Sonnet 4.5 and Kimi K2 share 3 comparable benchmark results. 1 of 8 categories are comparable. 9 results are unique to Claude Sonnet 4.5; 11 to Kimi K2.

Updated July 22, 2026
Shared results
3
Claude Sonnet 4.5 only
9
Kimi K2 only
11
Comparable categories
1 / 8

Pick Claude Sonnet 4.5 if you want the stronger benchmark profile. Kimi K2 only becomes the better choice if mathematics is the priority or you want the cheaper token bill.

Confidence note. This is a partial-evidence comparison with 3 shared benchmark results across 2 evidence categories; 1 of 8 categories currently have scoreable aggregates for both models. Treat the verdict as directional until coverage is more balanced.

Why this result

Claude Sonnet 4.5 is clearly ahead on the BenchAlign aggregate, 53.61 to 27.19. The gap is large enough that you do not need to squint at the spreadsheet to see the difference.

Claude Sonnet 4.5 is also the more expensive model on tokens at $3.00 input / $15.00 output per 1M tokens, versus $0.60 input / $2.50 output per 1M tokens for Kimi K2. That is roughly 6.0x on output cost alone. Claude Sonnet 4.5 gives you the larger context window at 200K, compared with 128K for Kimi K2.

Category breakdown

Exact category averages are shown below. Not measured means BenchLM does not have enough sourced public coverage for that model and category.

Category scores and score margins for Claude Sonnet 4.5 and Kimi K2
CategoryClaude Sonnet 4.5ΔKimi K2
MathClaude Sonnet 4.511.2Margin→ 4.9Kimi K216.1
AgenticClaude Sonnet 4.555.4MarginNo overlapKimi K2Not measured
CodingClaude Sonnet 4.577.2MarginNo overlapKimi K2Not measured
ReasoningClaude Sonnet 4.513.6MarginNo overlapKimi K2Not measured
KnowledgeClaude Sonnet 4.583.4MarginNo overlapKimi K2Not measured

Decisive benchmark drivers

The largest measured benchmark gaps in this matchup, with exact reported values.

More
A · Claude Sonnet 4.5B · Kimi K2

  1. FrontierMath v2 (Tiers 1-3)

    Math
    Source ↗
    A 13.495%B 21.404%
    Winner: Kimi K2Δ 7.9
    FrontierMath v2 (Tiers 1-3): Claude Sonnet 4.5 scored 13.495%; Kimi K2 scored 21.404%. Kimi K2 wins this benchmark.

  2. FrontierMath v2 (Tier 4)

    Math
    Source ↗
    A 4.167%B 0.000%
    Winner: Claude Sonnet 4.5Δ 4.2
    FrontierMath v2 (Tier 4): Claude Sonnet 4.5 scored 4.167%; Kimi K2 scored 0.000%. Claude Sonnet 4.5 wins this benchmark.

Operational comparison

Runtime and commercial metrics are compared only when both models have a complete sourced value.

MetricClaude Sonnet 4.5Kimi K2Comparison
Input / output priceUSD per 1M tokensClaude Sonnet 4.5$3 input / $15 outputKimi K2$0.6 input / $2.5 outputKimi K2 has the lower combined listed price.
Generation speedtokens per secondClaude Sonnet 4.5Not availableKimi K243 tok/sA complete speed comparison is not available.
First-answer latencyseconds to first tokenClaude Sonnet 4.5Not availableKimi K21.51 sA complete latency comparison is not available.
Context windowmaximum listed tokensClaude Sonnet 4.5200KKimi K2128KClaude Sonnet 4.5 lists the larger context window.

Benchmark Deep Dive

Agentic
BenchmarkClaude Sonnet 4.5Kimi K2Result
Terminal-Bench 2.0Source 50%—Not comparable
OSWorld-VerifiedSource 61.4%—Not comparable
VITA-BenchSource 17.0%—Not comparable
Gert LabsSource 48.51%—Not comparable
JobBenchSource 27.7%—Not comparable
τ²-bench resultsSource —61.1%Not comparable
Coding
BenchmarkClaude Sonnet 4.5Kimi K2Result
SWE-bench VerifiedSource 77.2%—Not comparable
AA-SciCodeSource —34.5%Not comparable
Reasoning
BenchmarkClaude Sonnet 4.5Kimi K2Result
ARC-AGI-2Source 13.6%—Not comparable
AA-LCRSource —51.0%Not comparable
CritPtSource —0.0%Not comparable
Knowledge
BenchmarkClaude Sonnet 4.5Kimi K2Result
GPQASource 83.4%—Not comparable
Artificial Analysis Intelligence IndexSource —19.4%Not comparable
AA-GPQA DiamondSource —76.6%Not comparable
AA-HLESource —7.0%Not comparable
AA-Omniscience IndexSource —-27.5%Not comparable
AA-Omniscience AccuracySource —26.8%Not comparable
AA-Omniscience Hallucination RateSource —74.2%Not comparable
MathKimi K2 wins
BenchmarkClaude Sonnet 4.5Kimi K2Result
AIME 2025Source 87%—Not comparable
FrontierMath v2 (Tiers 1-3)Source 13.495%21.404%Kimi K2 leads
FrontierMath v2 (Tier 4)Source 4.167%0.000%Claude Sonnet 4.5 leads
Multimodal
BenchmarkClaude Sonnet 4.5Kimi K2Result
Design Arena WebsiteSource 12191080Claude Sonnet 4.5 leads
Inst. Following
BenchmarkClaude Sonnet 4.5Kimi K2Result
AA-IFBenchSource —41.5%Not comparable
Frequently Asked Questions (2)

Which is better, Claude Sonnet 4.5 or Kimi K2?

Claude Sonnet 4.5 is ahead on BenchLM's BenchAlign leaderboard, 53.61 to 27.19. The biggest single separator in this matchup is FrontierMath v2 (Tiers 1-3), where the scores are 13.495% and 21.404%.

Which is better for math, Claude Sonnet 4.5 or Kimi K2?

Kimi K2 has the edge for math in this comparison, averaging 16.1 versus 11.2. Inside this category, FrontierMath v2 (Tiers 1-3) is the benchmark that creates the most daylight between them.

Related Comparisons

Explore More

Anthropic Compare Pricing Methodology Find Your Best LLM Overall Rankings
Last updated: July 22, 2026

Choose a model with this week’s evidence

Join 2,000+ readers for ranking moves, pricing changes, and the claims that still need proof.

One email each week. Unsubscribe anytime.