Claude context window calculator
Plan how much room your Claude context bundle needs before you upload files or paste a large source package.
Claude Opus 4.8 budget planner
Claude Opus 4.8 supports a 1M-token context window and up to 128K output tokens via the standard Messages API.
Source: Anthropic documentation. Last reviewed 2026-06-05.
Frequently asked questions
What context windows does this calculator use for Claude?
It shows all three current Claude 4 variants: Opus 4.8 (1M tokens), Sonnet 4.6 (1M tokens), and Haiku 4.5 (200K tokens). Select any variant to plan your budget.
Should I fill the whole Claude context window?
Usually no. Reserve room for your instructions and the response. A focused 60K-token bundle can outperform a noisy 190K-token dump.
Can Riflet build the source context?
Yes. Riflet can combine folders, PDFs, websites, GitHub repos, Obsidian vaults, and Notion exports into a portable context file for Claude.
Does Riflet update Claude Projects automatically?
No. Riflet exports the file. You choose when to upload or replace it in Claude.