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About this tool
Turn a source word count and a compression ratio into a target length, sentence count, token budget and reading time saved.
The Summary Length Planner converts a source word count and a compression choice into a concrete target: how many words the summary should be, roughly how many sentences and paragraphs that is at 17 words per sentence, the token budget at the 100-tokens-to-75-words rule, and the reading time saved at 238 words per minute. Pick a preset — one-line takeaway, TL;DR, APA abstract of 150–250 words, executive summary at about 10% — or set your own ratio, and it also writes a prompt that pins an AI assistant to that exact length. It is for writers and editors who need to commission or brief a summary before anyone starts drafting.
Open Summary Length Planner on AltFTool — it loads instantly in your browser.
Paste or type the text you're working with.
Choose how it should be transformed or analyzed.
Copy the finished text into your document or post.
You get sentence and paragraph estimates alongside the word count, so the target is something a writer can actually structure.
Density bands mark 30% as a light edit, 15% as arguments without examples and 5% as claims only, so the brief matches what is achievable.
It builds a length-locked instruction with the target words, the compression factor and a ±10% tolerance ready to paste into any assistant.
The common conventions are about 10% of the source for an executive summary, 15% for a bullet digest and around 5% for a chapter or section summary. Fixed-length formats are different: an APA-style abstract is 150–250 words regardless of how long the paper is.
About 0.75 words per token for English, the published rule of thumb that 100 tokens is roughly 75 words. The planner shows both the source and target token counts so you can size an API call or check a context limit.
238 words per minute, the mean silent reading rate for adult non-fiction from Brysbaert's 2019 meta-analysis of 190 studies. You can change it anywhere between 80 and 1000 wpm if your audience reads faster or slower.
Divide by about 17 words per sentence, the midpoint of the 15–20 range plain-English style guides recommend, and group roughly three sentences per paragraph. A 200-word summary is therefore about 12 sentences across four short paragraphs.