RAG chunk calculator

Client

Given a total length, chunk size, and overlap, estimate how many sliding windows you need—useful when planning retrieval-augmented generation (RAG) pipelines. Pair with the token estimate when your limits are in tokens.

Sliding-window count

The first chunk covers the first chunk size units. Each next chunk starts chunk size − overlap units after the previous start, until the rest of the document fits in one final window. Empty length yields zero chunks.

Parameters

?

Lengths are in one unit you choose (characters or tokens)—stay consistent. This counts overlapping sliding windows: each chunk starts after the previous by chunkSize − overlap. Real pipelines may add sentence boundaries or tokenizer steps.

Stride (chunk − overlap)
448
Approx. chunk count
112

URL query: ?len=50000&chunk=512&overlap=64

Common use cases

  • Ballpark how many vectors or embedding API calls you need before splitting real documents.
  • Compare overlap settings when tuning stride versus redundant content between chunks.
  • Teach RAG concepts using fixed numbers before adding sentence-aware splitters.

Common mistakes to avoid

  • Forgetting tokenizer vs character chunks

    If your pipeline chunks by tokens, measure length in tokens everywhere. Mixing characters here with token chunk sizes elsewhere skews counts.

  • Assuming chunks align with sentence boundaries

    This calculator uses a pure sliding window. Production RAG often snaps to sentences or paragraphs.

FAQ

What unit should I use for length and chunk size?

Any consistent unit—characters, tokens, or abstract units—as long as document length, chunk size, and overlap use the same one.

Is document text sent to a server?

No. Only the three numbers you type are used in your browser. There is no upload field on this page.

More tools

Related utilities you can open in another tab—mostly client-side.