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The forgetting curve, and what spaced review does to it

Move the review toggles below and watch a modeled retention curve respond. The diamond markers are Ebbinghaus's own reported data — real measurements, not a smooth invented curve. No signup, no email, free to embed on your own site.

The forgetting curve: measured data vs. modeled decayWithout review, the modeled curve predicts about 0 percent retention at 31 days. Toggle a review day below to see the modeled curve with spaced retrieval.0%50%100%30 min1 day1 week1 monthMeasured — Ebbinghaus (1885)Modeled — no reviewModeled — with reviews (illustrative schedule)

No reviews selected. Toggle a day above to add a spaced review.

Measured vs. modeled

The diamond markers are Ebbinghaus's own reported savings percentages — real, measured data, not an invented curve. Everything else on the chart, including both lines, is a modeled illustration: a simple decay curve, and that same curve recomputed with retrieval boosts at the days you toggle. The review schedule here is illustrative — MasterTheBook's actual spaced-review schedule adapts to your performance rather than following fixed days.

The measured points are from . The modeled spacing effect is illustrated per .

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<iframe src="https://masterthebook.com/tools/forgetting-curve/embed" title="The forgetting curve and the spacing effect — interactive chart" loading="lazy" style="width:100%;max-width:720px;aspect-ratio:4/3;border:0"></iframe>

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For educators, newsletters, and communities teaching retrieval practice or adaptive spaced review: use the snippet above as a two-minute demo. Companion reading — how to study a book, why you forget what you read, how to remember a nonfiction book, and why this works — each with named citations.

Want the fuller 1885 explanation behind the measured points? The forgetting curve, explained is the companion guide — original data, common distortions, and what later spacing research added.