Guide to Anki Intervals and Learning Steps

Learn how Anki calculates intervals and how you can modify settings to optimize your learning!

NOTE: There is a mistake towards the end of the video when I was talking about ideal retention rates of 80-90% and said what I would do if I had a retention rate of 96%, I should have INCREASED the interval modifier (to see cards less frequently) not decreased it.

00:00 Introduction
00:15 Why learn about Anki's algorithm
00:52 Type of cards
01:23 How intervals are calculated
03:18 Ease vs Interval modifier
05:50 How answers modify ease factor
06:49 How answers modify interval
11:05 Don't get stuck in "Ease Hell"
12:34 Learning phase
18:41 Longer learning steps are better
22:23 Aim for 80-90% success rate
25:26 How to achieve ideal retention rate
28:14 Summary

For medical students:
If you're aiming for very long term retention I would continue to recommend a 1d 6d 15d learning interval.
For a somewhat shorter term goal such as Step 1, you may want to aim for higher than 80-90% retention. I personally would recommend experimenting between shorter intervals (1d 3d 7d, 1d 4d 10d, 1d 3d 6d 15d) approach to allow yourself to see the cards a few extra times before your exam.

Please let me know in the comments if you have any questions :)

Recommended sources:

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[vanessatrinh]

1. Types of Cards

- New = Blue
- Learning/Re-learning = Red
- Graduated = Green


2. How intervals are calculated (for graduated cards)

- New interval = current interval *ease*interval modifier
- Default starting ease = 250%
- Default interval modifier = 100%
E.g.
Suppose you have a card with current interval of 10 days. Then if you have marked the card as Good, the next time Anki will show the card is: 10*2.5*1 = 25 days. At this point if you mark it as Good, the next time Anki will show the card is 25*2.5*1 = 62 days.


3. Ease factor vs. Interval modifier

- Ease applies to individual cards. Each card has its own ease factor associated with it no matter which deck you move it to.
- Interval modifier applies to decks. The whole deck has interval modifier associated with it.
E.g.

Deck 1 (interval modifier = 100%):

Card 1 (10d interval): Ease = 265% —> New interval = 10*2.65*1= 26 d

Card 2 (10d interval): Ease = 210% —> New interval = 10*2.10*1 = 21 d

Deck 2 (interval modifier = 80%).

Suppose Card 1 is moved to Deck 2. Now Card 1’s new interval is = 10*2.65*0.8 = 17 d

Lower interval modifier makes cards appear at higher frequency.


4. How answers modify ease factor (for graduated cards)

- Good = ease remains unchanged
- Again = subtract 20% from ease
- Hard = subtract 15% from ease
- Easy = add 15% to ease

5. How answers modify interval (for graduated cards)

- Good = current interval *ease*interval modifier

- Again = relearning step.
Each again is a “lapse”.

If relearning step is answered incorrectly, card is shown again in the Step (minutes).

If relearning step is answered correctly, the new interval is determined as a % of the old interval.

E.g. Suppose old interval is 10 days. Then if new interval say 0% —> card shows again the next day. If new interval is 70% —> show card again in 70% or 7 days.

Compare default settings vs the guy’s settings at 7:34. He uses Steps (in mins) of 20, New interval of 70%, Min interval of 2 days, and Leech action of Tag Only.

- Hard = current interval *1.2*interval modifier

- Easy = current interval *ease*interval modifier *easy bonus


6. Don’t get stuck in “Ease hell”

“Ease hell” affects graduated cards.

Suppose new card has interval of 5d —> If mark Good, you see it again in 5*2.5*1 = 12 days —> If mark Good, see it again in 12*2.5*1 = 30 days —> If mark Good, see it again in 30*2.5*1 = 75 days.

Suppose a different card also has interval of 5d —> If mark Again or Hard frequently, its interval drop to lowest possible, which is 1.3. Then see it again, and mark Good, see again in 5*1.3*1 = 6d —> Mark Good, see again in 6*1.3*1 = 8d —> Mark Good, see again in 8*1.3*1 = 10d.

—> Thus, you see low-ease factor cards too often sometimes, or “ease hell”.


7. Learning Phase

Answering a card incorrectly in the learning phase does not change its ease factor and does not count towards the lapses. These things only happen in review phase with graduated cards.

At any time in the learning process you get the card wrong, Anki goes back to the first step in the Steps (in mins) until you get the card right.

—> Thus, should increase learning steps so you can learn the cards well enough before cards are graduated.

Compare Default vs. his settings at 14:04. His settings: Steps (in mins) are 15 1440 8640. Graduating interval is 15 days. Easy interval is 60 days.


8. Longer learning steps are better

- Longer intervals build stronger memory
- Longer intervals are more efficient
SuperMemo 2 (1987):

Interval 1 = 1 day

Interval 2 = 6 days

Then Interval = previous interval *ease factor

Barhrick Study (1993): longer study intervals are better

Rohrer and Pashler (2007): having too little spacing is worse than having too much.


9. Aim for 80-90% retention rate

Aim for True retention rate of 80 - 90%. If >90%, cards may be too easy and/or review too frequently. If <80%, cards may be too difficult and/or review too sporadically.


10. How to achieve ideal retention rate

- Periodically check your retention statistics. Check the Statistics tab to get True retention of mature cards within 80-90%.

- Modify interval modifier accordingly. If needs to change, change Interval modifier by going to deck overview —> Settings icon —> Options —> Reviews —> Interval modifier. Check Anki manual for an equation to calculate the appropriate modifier (at Anki manual site —> Deck Options —> Reviews).

- Improve quality of cards. Read SuperMemo site “20 rules of knowledge formulation”.

[gsmendoza]

I need to create an Anki deck to remember all these terms...

[AlcantaraCaio]

I changed my settings after seeing this video a couple of months ago, now everytime I'm going to talk about anki to someone, the first thing that I do is sending this video. Great job!

[TuringMachine]

*Summary of the technical details* (please watch the video for the intuition)

# *Phases*
## _Learning Phase_
By default, there's a test after one minute and another after 10 additional minutes. If you fail any of these tests, you go back to the first one. Once you complete them all, the card is shown, by default, the next day and goes to the Reviewing Phase. If you click the Easy Button at any point, the card will be shown four days later and it will skip immediately to the Reviewing Phase.

## _Reviewing Phase (aka, when the card is Graduated)_
You are tested indefinitely after progressively longer intervals. If you fail, you enter the Relearning Phase. The intervals are computed with the formulas explained below.

## _Relearning Phase_
You are tested every 10 minutes, by default, until you succeed. The new interval will be, by default, 0% of the interval immediately before entering the relearning step; so it will be the minimum interval, which, by default, is one day.


# *Interval formulas for Reviewing Phase*
A different formula for computing the interval (to the next time the card is shown) is used depending on your recall performance:

* Again: go to relearning phase
* Hard: Current Interval * 1.2 * Interval Modifier
* Good: Current Interval * Ease * Interval Modifier
* Easy: Current Interval * Ease * Interval Modifier * Easy Bonus

The factors used above are defined as follows.

## _Ease_
The Ease is a property of the card.
By default, it starts at 250%.
Its minimum value is 130%.
During the Reviewing Phase, it changes depending on your recall performance:

* Again: -20%
* Hard: -15%
* Good: +0%
* Easy: +15%

## _Interval Modifier_
The Interval Modifier is a property of the deck.
By default, it is 100%.

## _Easy Bonus_
The Easy Bonus is a property of the deck.
By default, it is 130%.

[rodrigodasilvalandim]

Yours are the best video regarding anki configuration on YouTube. I'm completely tired of 20-minutes long videos from a random guy talking nonsenses and only teaching 3 steps that wouldn't take 2 minutos to be explained. Thank you, lad!

[micheledonatelli]

This video should be adopted in the official Anki guide... so far the most useful guide ever!
I was also stuck in the ease loop and that was frustrating, and now I'm out of it, productive and happy.
THANK YOU SO MUCH!

[jeevanmarg]

One of the best explanations of Anki Intervals, hands down. Thank you so much.

[jemand]

this is honestly one of the most helpful and well-done videos on youtube. Thanks for that! Looking forward to your next videos, it's always good to see other medicine students having the same mindset :)

[karanrandhawa]

Finally, an excellent in-depth video on Anki's settings that is clear and easy to follow. Thank you!

[diegogutierrez]

Absolutely, the best explanation about Anki configuration. Actually many channels recommend a certain configuration, but they don't know the basis and also it is not the best configuration. 2021.

[TheZerept]

Thank you very much! 😭
This a wonderfull presentation. Especially "Ease vs Interval modifier" became very clear for me.
It is well structured and were 30min well spend! I learned so much! Now I don´t have to rely on recommendation from others anymore.

[nataliatrusova]

So far this is the best explanation I've ever seen

[alessbritish]

I spent nearly two hours replaying this video, I think I got it now. Thank you! Anki is surely more handy now.

[miumiumiaomi]

this is gold. I have tried anki for now like the fifth time now. somehow could not get into it. the reason I retried it again and again is that I heard from my friends, on line, teacher...various source of how good it is compared to others. and I was thinking to integrate the forget curve to it. This answers all my questions! thank you so much!!

[myvideospersonal]

My god, this was so helpful! I wanted to geek out about how the intervals really work and this video is perfect.

[dakotapdx]

Super useful! I've used Anki consistently for awhile and am totally in "ease hell." Just modified all my settings and am looking forward to the change! Thanks for putting this together.

[developerninja]

16:10 you've got a misconception. If you hit the 'Again' button after a card is graduated, it will not go back to the learning phase, instead it's going to be considered a "lapse" and then you will have to go through the "relearning" steps

[Subhamkumar-rpmt]

Please make an updated video about anki with new settings and v3 scheduler. If possible please explain us about the FSRS4Anki Helper addon too.

[faiziiiiii]

One of my top 10 videos of the year, Thank you for taking the time to explain these ideas.

[prins]

After days of watching videos on Youtube, this is the only one that explains well the anki algorithms. Nice job!! I understand now better how frequently my cards appear. 😁😁