Work out memory retention estimate instantly with clear inputs, formula shown and shareable results.
This uses the exponential forgetting curve R = e^(-t / S), where S is the stability of the memory in days; half-life follows as S x ln 2. The curve is steepest immediately after learning, so a review on day one buys far more retention than the same review a fortnight later.
Forgetting curve
R = e^(-t / S), with t the elapsed days and S the memory stability
Half-life
time to 50% recall = S x ln(2) = 0.693 x S
R = e^(-t / S), with t the elapsed days and S the memory stability. This uses the exponential forgetting curve R = e^(-t / S), where S is the stability of the memory in days; half-life follows as S x ln 2.
The curve is steepest immediately after learning, so a review on day one buys far more retention than the same review a fortnight later.
Enter time since studying, memory stability. The defaults shown are a realistic worked example — swap in your own figures to get a result you can use.