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Spaced Repetition Schedule Calculator

Work out spaced repetition schedule instantly with clear inputs, formula shown and shareable results.

About Spaced Repetition Schedule Calculator

Each interval is the previous one multiplied by the growth factor, and the review days are the running total of those intervals from the first study session. A geometric schedule keeps total review effort almost flat while retention keeps climbing, which is why six reviews can cover months rather than weeks.

Formulas

Interval sequence

interval(k) = first interval x multiplier^(k - 1)

Review day

review day(k) = sum of intervals 1 through k

Worked example

With the default values below, Spaced Repetition Schedule Calculator returns Schedule covers of 162.1. Change any input above and every figure here is recalculated in your browser.

Inputs used

First intervalminimum 0.5 days
1 days
Interval multiplierminimum 1.1
2.5
Number of reviewsaccepts 1–20
6

Results

Schedule covers
162.1 days
Review days
Day 1, day 3.5, day 9.8, day 25.4, day 64.4, day 162.1
Final gap between reviews
97.7 days
Average gap
27.0 days

Step by step

  1. 1Values used
  2. 2Interval sequence
  3. 3Review day
  4. 4Schedule covers= 162.1 days
  5. 5Review days= Day 1, day 3.5, day 9.8, day 25.4, day 64.4, day 162.1
  6. 6Final gap between reviews= 97.7 days
  7. 7Average gap= 27.0 days

Assumptions and limits

  • The result is derived only from the 3 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 1 decimal place, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

How is the Spaced Repetition Schedule figure worked out?

interval(k) = first interval x multiplier^(k - 1). Each interval is the previous one multiplied by the growth factor, and the review days are the running total of those intervals from the first study session.

Why does this matter?

A geometric schedule keeps total review effort almost flat while retention keeps climbing, which is why six reviews can cover months rather than weeks.

What do I need to enter?

Enter first interval, interval multiplier, number of reviews. The defaults shown are a realistic worked example — swap in your own figures to get a result you can use.

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