Flashcard Review Date Calculator
Given today's review, compute the next review date for a flashcard and forecast the following three stages using the SM-2 ease factor.
| Stage | Interval | Review date |
|---|---|---|
How the flashcard review scheduler works
This calculator combines a simple date shift with the SM-2 interval growth rule. Given your last review date and current interval, it computes the next scheduled review date by adding the interval in days. It then projects the following three stages by multiplying the previous interval by the ease factor, showing when each review would land if every future recall is successful.
The projection assumes you answer quality ≥ 3 (successful recall) every time. A single failed recall resets the card to a 1-day interval in the SM-2 algorithm, so these dates are best-case estimates. Think of the forecast as "how spaced my reviews will be if I stay consistent" rather than a guarantee.
The formula
Next review date = last review date + interval days.
Forecast stage N interval = stage (N−1) interval × ease factor.
Forecast stage N date = stage (N−1) date + stage N interval.
A worked example
Last review was March 1. Current interval is 6 days, ease factor 2.5. The calculator shows:
- Stage 1: 6 days → March 7.
- Stage 2: 6 × 2.5 = 15 days → March 22.
- Stage 3: 15 × 2.5 = 37.5 days → April 28.
- Stage 4: 37.5 × 2.5 = 93.75 days → August 1.
Notice how quickly intervals grow. By stage 4 you are reviewing the card roughly quarterly. Stage 5 would push the next review past a full year. This exponential growth is the spacing effect in action — well-learned material rarely needs frequent review.
Why the ease factor matters so much
Ease factor sets the multiplier for every future stage. A card at EF 2.5 grows 2.5× per successful review; a stubborn card at EF 1.3 grows only 1.3× and accumulates many more reviews per month. Over a year, the difference between EF 2.5 and EF 1.3 means the difference between 5 reviews and 20+ reviews for the same card. Choose your recall quality honestly — inflated scores push EF up and cause you to forget cards you had not actually mastered.
Choosing the right ease factor
Default is 2.5 for new cards. Anki users can check a specific card's current EF in the browser. If you do not know, start with 2.5. Cards that consistently feel easy will drift to 2.7–3.0; stubborn cards can bottom out at the 1.3 floor. You do not set EF directly in SM-2 — it updates automatically based on your recall quality.
Common mistakes
- Treating the forecast as a plan. These are projections assuming uninterrupted success. Real decks have failures that reset individual cards. Use the forecast for planning review volume, not for locking in specific dates.
- Changing EF manually after every review. In SM-2, EF is a function of your recall quality over time, not a slider you adjust. This calculator lets you set it for modelling, but in real use it self-adjusts.
- Comparing output exactly to Anki. Anki uses variants of SM-2 plus interval modifiers, so the dates here may differ by a day or two. Treat this as an SM-2 baseline, not an Anki replica.
- Forgetting time zones. Anki and most apps handle dates in your local time zone; this calculator does the same. Travel can shift a review by a day.
What this calculator is not
It does not replace a flashcard application — there is no card storage, no review button, no statistics. It is a math tool for understanding when your next reviews would fall given an SM-2 schedule. For real study, use Anki, SuperMemo, Mnemosyne, or another dedicated tool.