Forgetting Curve Planner Calculator

Planner inputs

Formula used

The planner uses a classic exponential forgetting curve: R(t) = e^{−t / S}, where R(t) is predicted retention after t days and S is a stability constant (in days).

• Difficulty lowers S, causing faster decay.
• Initial mastery increases S, slowing decay.
• Each review multiplies stability by a gain factor (e.g., ×1.70).
• Reviews are scheduled when retention falls to chosen thresholds (e.g., 85% → 75% → 65%).

To find the day a threshold is reached, the planner solves: t = −S · ln(threshold), rounded up to whole days.

How to use this calculator

1. Enter your start date and exam date.
2. Set total topics and your daily available minutes.
3. Choose minutes per new topic and per review.
4. Select a review style, then adjust difficulty and mastery.
5. Press Create plan to generate your daily schedule.
6. Download CSV or PDF, then track your real progress daily.

Retention targets and thresholds

Choose thresholds that match your exam stakes and syllabus size. Balanced mode uses 85%, 75%, 65%, and 55% retention points to trigger reviews. Conservative adds earlier checks like 90% and 85% to reduce forgetting spikes. Aggressive schedules fewer reviews, which suits short timelines or highly familiar topics. Custom thresholds let you mirror your own score drop pattern from practice tests.

Stability and difficulty calibration

The planner starts each topic with a stability value (S) that controls how quickly recall fades. Higher initial mastery increases S, while higher difficulty decreases it. In typical settings, base stability lands between about 0.6 and 6.0 days, so early reviews can be close together. If your mock scores stay high after two days, raise initial mastery or lower difficulty. If you forget quickly, do the opposite.

Daily capacity and overload control

Workload is built from minutes per new topic and minutes per review. The schedule displays total minutes and a load percentage against your daily limit, so you can spot crunch days immediately. For example, with 90 minutes/day, 12 minutes per new topic, and 5 minutes per review, three new topics plus six reviews takes 66 minutes, or 73% load. Use buffers for weak areas and timed drills.

Spacing pattern toward the exam

Reviews are timed by solving t = −S·ln(threshold), then rounding to whole days. With S = 3.0 days, reaching 75% retention happens near day 1, while 55% happens near day 2. As you review, stability multiplies by the gain factor, so later reviews spread out naturally. If predicted exam retention falls below your target, the planner adds a late review window to protect final recall.

Using exports for tracking

CSV export is ideal for tracking completion, adding “done” flags, and filtering missed sessions. Sort by load to plan catch-up days, and color overload rows for quick attention. PDF export is best for printing and pinning near your desk. After each practice test, adjust difficulty, mastery, and review gain so the next plan matches your real forgetting speed. Keep predicted retention above target while maintaining a sustainable routine across all study days consistently.

FAQs

How is the review date calculated?

The planner estimates retention with an exponential curve and schedules a review when retention hits your selected threshold. It solves t = −S·ln(threshold), converts the result to whole days, then shifts sessions to study days if weekends are excluded.

What does predicted exam retention mean?

It is the average predicted recall level on the exam date across all topics, based on each topic’s last planned touch and current stability. Use it as a planning signal, not a guarantee.

Which review style should I choose?

Conservative fits high-stakes exams and weaker recall. Balanced suits most learners with steady daily time. Aggressive reduces reviews when time is tight or topics are already familiar. Custom is best when you have practice-test retention data.

How should I set minutes per new topic and review?

Use a realistic average from your recent sessions. New-topic time should include understanding and quick notes. Review time should reflect active recall, not rereading. If you use timed questions, include their minutes in the review estimate.

What if the plan shows many overload days?

Start earlier, raise daily minutes, reduce new-topic minutes by simplifying notes, or switch to a more aggressive mode. You can also split heavy review days by moving some reviews one day earlier, keeping thresholds similar.

Can I plan with named topics?

Yes. Paste one topic per line in the Topic names field. The planner will use your labels in exports and scheduling, making it easier to track completion and identify weak areas.

Example data table

Sample week showing how new topics and reviews may look.

Your real plan will adapt to your dates, workload, and review style.