SRS stages

The HanziHero spaced repetition system has ten total stages. You can think of them more like buckets which approximate how well you know a card. These stages can be broken down into six different groups. The groups, in order, are:

Novice -> Apprentice -> Journeyman -> Expert -> Master

Each of those groups have stages of their own, besides the last one:

  • Novice I
  • Novice II
  • Apprentice I
  • Apprentice II
  • Journeyman I
  • Journeyman II
  • Expert I
  • Expert II
  • Expert III
  • Master

How it works

Depending on whether you answer an item correctly or incorrectly in your reviews, we calculate the amount of time until you see the card again, or in other words, the next interval.

The pseudocode for computing the “next interval” is as follows:

if total_incorrect > 0:
  next_interval = interval * 0.5
else if interval == 1:
  next_interval = 4 + days_overdue * 0.5
  next_interval = (interval + days_overdue * 0.5) * 1.8

final_next_interval = max(1, ceil(next_interval + fuzz))

In plain English:

  • IF the present interval is exactly 1 day (i.e., the item was just learned), then the next interval will be four plus half of the number of days overdue.
  • IF the number of incorrect answers is greater than zero, then the next interval is half of the present interval.
  • OTHERWISE the next interval is the present interval combined with half of the number of days overdue, with that entire result then being multiplied by 1.8.

Additionally, we add in some random “fuzz” number to help spread out the days that future reviews are scheduled on. Otherwise one may end up having 400+ reviews on one day, and zero on the next!

The fuzz factor scales with the interval, from ±1 to ±4.

How well do I know a subject at each stage?

Novice: You need to review this item nearly every day.

Apprentice: You need to review this item at least once a week.

Journeyman: You need to review this item around once a month.

Expert: You need to review this item bimonthly or less frequently.

Master: You have memorized this item.

What are the timings for each stage?

Here are the timing thresholds for each stage. So, for example, any item that has an interval greater than 1 day but less than 4 days would be considered Novice II.

  • Novice I - 1 day
  • Novice II - 4 days
  • Apprentice I - 1 week
  • Apprentice II - 2 weeks
  • Journeyman I - 1 month
  • Journeyman II - 2 months
  • Expert I - 4 months
  • Expert II - 8 months
  • Expert III - 1 year