Context Window

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Kimi K2p5 vs Openai Gpt 5 Nano

This page is context-first: how much text each model can take in one request. Full specs adds capabilities and limits; the pricing matrix below is only about $/million tokens from hosts that list both models.

Moonshot

Model

Kimi K2p5

Tool calling

Context window

262K

262,144 tokens · ~197K words

Model page
Openai

Model

Openai Gpt 5 Nano

Tool calling

Context window

5M

5,000,000 tokens · ~3.8M words

Model page

Context window · side by side

Bar length is relative to the larger of the two windows (100% = max of this pair). This is not pricing.

Kimi K2p5262K
Openai Gpt 5 Nano5M

Openai Gpt 5 Nano has about 19.1× the context window of the other in this pair.

Token calculator →Memory savings →

Openai Gpt 5 Nano has 1807% more context capacity (5000K vs 262K tokens). Openai Gpt 5 Nano is 75% cheaper on input.

Quick verdicts

Short takeaways — validate with your own workloads.

  • Long document processing

    Use Openai Gpt 5 Nano. Its 5000K context fits entire documents without chunking (vs 262K).

  • RAG / high-volume retrieval

    Use Openai Gpt 5 Nano. Input tokens are 75% cheaper — critical when sending large retrieved contexts.

  • Long output (reports, code files)

    Use Kimi K2p5. Its 262K max output lets you generate complete artifacts in one request.

Full specs

Context, output, capabilities, and dates. Green highlights the favorable value where we compute a winner.

SpecKimi K2p5Openai Gpt 5 Nano
Context window262,144 tokens (262K)5,000,000 tokens (5000K)
Max output tokens262,144 tokens (262K)16,384 tokens (16K)
Speed tierBalancedFast
VisionNoNo
Function callingYesYes
Extended thinkingNoNo
Prompt cachingYesNo
Batch APINoNo
Release dateN/AN/A

Pricing matrix

Dollar rates only: hosts that list both models, per 1M tokens. For how much text fits, use the context section above — not this table.

ProviderKimi K2p5 inKimi K2p5 outOpenai Gpt 5 Nano inOpenai Gpt 5 Nano out
Fireworks$0.600/M$3.00/M——
Snowflake——$0.150/M$0.600/M

Frequently asked questions

Openai Gpt 5 Nano has a larger context window: 5000K tokens vs 262K. For long documents, large codebases, or extended agent sessions, the larger context window reduces the need to chunk inputs or summarize history.

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