Reading time is estimated from a single personal number: your reading speed in words per minute (wpm). The average adult reads silently at roughly 200 to 250 wpm for ordinary prose, college students often land near 300 wpm on familiar material, and dense technical or legal text can drag anyone down to 100 to 150 wpm. The formula is disarmingly simple: minutes = total words / words per minute. A 90,000-word novel at 250 wpm takes 360 minutes — 6 hours. Because few sources list word counts, the page-count shortcut helps: a typical paperback page holds 250 to 300 words, so a 300-page book is roughly 75,000 to 90,000 words.
Your effective speed depends on purpose as much as ability. Skimming for gist can exceed 400 wpm; studying — reading to remember, with notes and re-reads — often runs at half your casual speed. Comprehension is the constraint that matters: decades of research find that pushing speed much past your comfort zone trades understanding for velocity, which is why 'speed reading' courses that promise 1,000 wpm with full comprehension do not survive scientific scrutiny. For planning, use your honest study speed, not your aspirational one.
Use the estimate to plan realistically: a 6-hour book is not one evening but a week of 50-minute sessions, and a 40-page academic chapter at 150 wpm study speed is over two hours, not 'a quick read.' This calculator converts word or page counts to time at your speed, so reading lists become schedules instead of wishes.