Enter your app's observed retention - from any cohort you like - to generate a model.
Day 1 (D1) retention is the percentage of your users that return to the app the day after they install. In general, day n (Dn) retention is the percentage of users who return exactly n days after they install.
The retention curve is typically a function of the form r(n)=anb, where each app has its own values for the coefficient a and the exponent b that best fit their data. Dn retention is modelled (predicted) by r(n) for any value of n.
For example, if a game's retention curve is defined by the function
r(n) = 0.396 * n -0.472
then D120 retention is predicted to be
0.396 * 120 -0.472 = 0.041 = 4.1%
In other words, if 1,000 people install today, 41 are expected to use the app exactly 120 days later.