The SuperMemo 2 (SM-2) algorithm calculates intervals for spaced repetition learning. The steps are:

1. Split knowledge into distinct items.
2. Initialize E-Factor (easiness of memorizing) to 2.5 for all items.
3. Repeat items using the following intervals in days, where $I(n)$ is the interval after the $n$-th repetition:

• $I(1) := 1$
• $I(2) := 6$
• For $n > 2$: $I(n) := I(n-1) \times EF$

4. Assess the quality of the response ($q$) on a 0-5 scale: 5 (perfect), 4 (correct after hesitation), 3 (correct but difficult), 2 (incorrect, but correct answer seemed easy to recall), 1 (incorrect, but correct answer remembered), 0 (complete blackout).
5. Update the E-Factor using the formula: $EF_{new} := EF + (0.1 - (5-q) \times (0.08 + (5-q) \times 0.02))$. If $EF_{new} < 1.3$, set $EF_{new} = 1.3$.
6. If $q < 3$, repeat the item without changing the E-Factor.
7. Repeat the session until a grade of at least $q = 4$ is achieved for all items.