# Intervals for Lapses

Hey everyone,

I apology for posting/asking a lot at the moment… I want to know more how Anki calculates my intervals and I can’t find sufficient answers online. And since I am a little bit neurotic about this, I want to fully understand it
I have this card which is lapsing the first time. It has an interval of 1 day, an ease of 230% and the interval modifier is set on 80%. Therefore, the card should now get a interval of (12,30,8=1,84->) 2 days ( I assume Anki rounds due to normal rules). However, I get a 3 day interval.
I also checked on cards with an older interval: The interval shown in browser indeed is the current interval. There is not a hidden one somewhere.
I also checked switching the new interval option to 0% but it does not change the outcome.

Can someone explain me how the calculation with lapsing cards work?!

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Hey everyone,

how does Anki round?

I have several cards:
1.: (Interval: 8 days, Ease: 235%, Interval modifier: 80%, Lapses: 0). So the next Good interval thereby should be: 8 * 2,35 * 0,8 = 15,04, I get 15.
2.: (Interval: 2 days, Ease: 235%, Interval modifier: 80%, Lapses: 0). So the next Good interval thereby should be: 2 * 2,35 * 1 = 3,76, I get 4.
3.: (Interval: 9 days, Ease: 220%, Interval modifier: 80%, Lapses: 0). So the next Good interval thereby should be: 2 * 2,35 * 1 = 15,84, but here I get 15 and not 16. Can someone explain this?

Damien once wrote in an older post: “The old scheduler applies a 0-25% boost to learning steps to prevent them from appearing in a consistent order. The experimental scheduler reduces this boost to a few minutes, and doesn’t apply it at all if the card will be scheduled 1+ days in advance. This prevents cards from being scheduled an extra day due to that randomness.”.

But since I activated the 2.1 v, this should not cause any trouble.

Similar problem: I a lapsing card (Interval: 1 days, Ease: 210%, Interval modifier: 80%, Lapses: 2): 1 * 2,1 * 0,8 = 1.68. But for this card I get 3 day interval. Is it because of the laps. Do the laps interfere here?

I just want to know how Anki calculates the intervals in this

i don’t think the rounding is that important as anki uses fuzz factor in the end, making given interval different from calculated interval on the buttons. but i think that should be how it rounds the intervals up.

When you press a button that says 30 days, anki might give the card a different interval. it’s due to fuzz factor and doesn’t mean anki’s algorithm is broken or it’s not functioning properly.
anki automatically applies a fuzz factor to all cards so when you introduce some new cards, you won’t have to review all of them in the same day.

The fuzz factor is usually between 15 to 20 percent.

### Example

Here’s an example for you to understand fuzz factor better

Interval for card A: 10 days (on any button)
interval for card B: 20 days (on any button)
interval for card C: 30 days (on any button)
interval for card D: 40 days (on any button)

Now here’s the interval that we expect anki to give these cards:

for card A the interval should be something from 8 to 12 days
for card B the interval should be something from 16 to 24 days
for card C the interval should be something from 25 to 35 days
for card D the interval should be something from 34 to 46 days

Thank you for your answer!

But I ran some examples as well and I have to say that intervals shown under the buttons do not include the fuzz factor. Can it be that the fuzz factor gets added to the cards after I clicked on the button and therefore is kind of invisible?

So my questions (lapped algorithm and rounding) are still unclear

the fuzz gets added after you press the button, that’s why the interval that shows on the answer button might be different from the interval you see in card info window.

I guess we have a misunderstanding here. I want to know how Anki gets to the intervals given under the buttons. As you say correctly the Fuzz gets added after I click on the button, therefore cannot be the reason why

Similar problem: I a lapsing card (Interval: 1 days, Ease: 210%, Interval modifier: 80%, Lapses: 2): 1 * 2,1 * 0,8 = 1.68. But for this card I get 3 day interval.

this is “happening”

You understand that this works only for review cards?
Learn/re-learn card follow their steps and ease, interval modifier and previous interval don’t affect their steps.

Oh, I did not consider that! Thank you!