GPT-5.1 vs Kimi K2 Instruct
Wins 5 of 6 areas
Coding · Reasoning · Facts · Long documents · Following instructions
Wins 0 of 6 areas
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GPT-5.1 is the stronger all-rounder.Kimi K2 Instruct is cheaper.
Scores updated · 34 tests both models report · How we compare
Where each one wins
Tests won in each of the six areas where both have results. Each piece is one test, so a longer bar means more evidence; grey means the two scored within a point of each other.
- CodingWriting and fixing software40GPT-5.14 of 4 tests
- ReasoningHard problems that need careful thinking30GPT-5.13 of 3 tests
- FactsGetting facts right instead of making them up30GPT-5.13 of 3 tests
- Following instructionsDoing exactly what it is asked20GPT-5.12 of 2 tests
- Long documentsFinding answers in very long texts10GPT-5.11 of 1 test
- AgentsCarrying out multi-step tasks on its own11Even1 each
Long documents rests on a single test.
What it costs
Prices per million tokens, roughly 750,000 words. The bars show the cost of a million tokens read plus a million written.
Kimi K2 Instruct costs 72% less for the same work.
The biggest differences
The tests each model wins by the widest margin, up to three each. Scores are out of 100.
Where GPT-5.1 pulls ahead
- Finds hard-to-locate facts by browsing the webBrowseComp+36.7points ahead
- Recent programming contest problemsLiveCodeBench v6+33.3points ahead
- Follows unfamiliar, precisely checkable instructionsIFBench+31.2points ahead
Where Kimi K2 Instruct pulls ahead
- Real work tasks from 44 professionsGDPVal+1.9points ahead
Every test, side by side
All 34 tests both models report. The winning score is in its model's colour; marks a score checked independently.
CodingGPT-5.1
- LiveCodeBench v6GPT-5.1 by 33.38753.7+33.3
- Terminal-Bench HardGPT-5.1 by 2245.523.5+22
- SciCodeGPT-5.1 by 12.643.330.7+12.6
- SWE-bench VerifiedGPT-5.1 by 10.576.365.8+10.5
AgentsEven
- BrowseCompGPT-5.1 by 36.750.814.1+36.7
- GDPValKimi K2 Instruct by 1.916.318.2+1.9
ReasoningGPT-5.1
- Humanity's Last ExamGPT-5.1 by 22.128.56.4+22.1
- GPQA DiamondGPT-5.1 by 10.687.376.7+10.6
- CritPtGPT-5.1 by 4.94.90+4.9
FactsGPT-5.1
- AA-Omniscience · Non-hallucinationGPT-5.1 by 17.848.130.3+17.8
- AA-Omniscience · AccuracyGPT-5.1 by 12.337.725.4+12.3
- Vectara HHEM hallucination ratelower is betterGPT-5.1 by 5.812.117.9+5.8
Following instructionsGPT-5.1
- IFBenchGPT-5.1 by 31.272.941.7+31.2
- Multi-ChallengeGPT-5.1 by 9.363.454.1+9.3
Other results19 tests, not counted
Tests outside the eight areas. They are not counted above: several are summary scores built from other tests, or the same test under another name.
- AIME 2025GPT-5.1 by 44.59449.5+44.5
- AA-OmniscienceGPT-5.1 by 325.4-26.6+32
- Artificial Analysis Coding IndexGPT-5.1 by 23.549.425.9+23.5
- vectara_avg_summary_lengthGPT-5.1 by 195.2 rating points254.459.2+195.2 rating
- τ²-BenchGPT-5.1 by 16.982.765.8+16.9
- AA Agentic IndexKimi K2 Instruct by 16.121.637.7+16.1
- HLE (with tools)GPT-5.1 by 15.842.726.9+15.8
- AIR-Bench 2024GPT-5.1 by 12.186.274.1+12.1
- Tau2 airlineGPT-5.1 by 10.56756.5+10.5
- AA IntelligenceGPT-5.1 by 9.424.715.3+9.4
- τ²-Bench Telecom (AA run)GPT-5.1 by 8.581.973.4+8.5
- τ²-Bench (Retail)GPT-5.1 by 7.377.970.6+7.3
- MMLU-ProGPT-5.1 by 5.98781.1+5.9
- vectara_factual_consistencyGPT-5.1 by 5.887.982.1+5.8
- vectara_answer_rateGPT-5.1 by 1.410098.6+1.4
- anthropic_red_teamtie99.599.3tie
- HarmBenchtie97.697.4tie
- simple_safety_teststie99.8100tie
- XSTesttie98.298.2tie
Questions people ask
Which is better, GPT-5.1 or Kimi K2 Instruct?
GPT-5.1 wins five of the six areas where both have results: coding, reasoning, facts, long documents and following instructions. Kimi K2 Instruct wins none, but costs 72% less. They are level on agents.
Which is better for coding?
GPT-5.1. It wins 4 of the 4 coding tests both models report; Kimi K2 Instruct wins none.
Which is cheaper?
GPT-5.1 costs $1.25 per million input tokens and $10.00 per million output tokens; Kimi K2 Instruct costs $0.60 and $2.50. That makes Kimi K2 Instruct about 72% cheaper for the same work.
How do you compare the two?
We use the 34 benchmark tests both models have published scores on. The verdict counts the 15 tests in the eight capability areas, and a gap under one point (ten on rating-style scales) counts as a tie. The other 19 are listed but not counted, because several are summary scores or repeat a test. Each score is the one shown on the model's own page.