How much is forgotten after 24 hours?

Ebbinghaus found that without review, approximately 50–70% of newly learned material is forgotten within 24 hours. After one week, typically only 10–30% is retained. Meaningful material (connected to prior knowledge) decays more slowly than arbitrary information.

Does reviewing before sleep improve retention?

Research supports pre-sleep review: memory consolidation occurs during sleep, particularly during slow-wave sleep for declarative memory. Reviewing material immediately before sleep, then reviewing again 24 hours later, is approximately twice as effective as two equally spaced daytime reviews.

Ebbinghaus Forgetting Curve Retention Calculator

Formula Definitions

The Ebbinghaus Forgetting Curve Retention Calculator works by applying a well-defined formula to the values you enter. Understanding the formula behind the calculation helps you interpret the result and check that your inputs are correct. Below we break down the key components that drive the Forgetting Curve.

The core formula used by this calculator is:

Result = f(inputs, settings)

Each variable in the formula has a specific meaning:

inputs — Values entered into the Forgetting Curve.
settings — Options, units, or parameters that adjust how the calculation is performed.
Result — Computed output for the chosen inputs and settings.

How to Use This Calculator

Enter the required values. Enter the required values into the Ebbinghaus Forgetting Curve Retention Calculator input fields.
Adjust settings. Adjust any settings, select applicable options, or choose units as needed.
Calculate the result. Press Calculate to compute the result using the underlying formula.
Interpret the output. Review and interpret your result using the provided context, reference ranges, or explanatory notes.

Glossary and Definitions

Input: A value entered into the calculator to be processed.
Output: The computed result returned by the calculator for the given inputs.
Setting: An option that adjusts how the calculation is performed, such as unit selection or mode.
Ebbinghaus forgetting curve: A key concept referenced by the Forgetting Curve: Calculate memory retention R(t) = e^(−t/S) at time t using Ebbinghaus's forgetting curve, where S is memory stability. Predicts what percentage of learned material is retained after a given number of days without review.
Memory retention: A key concept referenced by the Forgetting Curve: Calculate memory retention R(t) = e^(−t/S) at time t using Ebbinghaus's forgetting curve, where S is memory stability. Predicts what percentage of learned material is retained after a given number of days without review.
Learning decay: A key concept referenced by the Forgetting Curve: Calculate memory retention R(t) = e^(−t/S) at time t using Ebbinghaus's forgetting curve, where S is memory stability. Predicts what percentage of learned material is retained after a given number of days without review.
Spaced repetition: A key concept referenced by the Forgetting Curve: Calculate memory retention R(t) = e^(−t/S) at time t using Ebbinghaus's forgetting curve, where S is memory stability. Predicts what percentage of learned material is retained after a given number of days without review.
Recall rate: A key concept referenced by the Forgetting Curve: Calculate memory retention R(t) = e^(−t/S) at time t using Ebbinghaus's forgetting curve, where S is memory stability. Predicts what percentage of learned material is retained after a given number of days without review.
Memory science: A key concept referenced by the Forgetting Curve: Calculate memory retention R(t) = e^(−t/S) at time t using Ebbinghaus's forgetting curve, where S is memory stability. Predicts what percentage of learned material is retained after a given number of days without review.