# Limits of SuperMemo

Have you ever wondered if there is a hard limit in SuperMemo? Here I will be recollecting my own findings.

#### How long will a trial version of SuperMemo work?

The credit is on the number of operations rather than natural time. There is no time limit. You can use it sparsely for a very long time. How many actions is a different question.

#### What is the limit of elements in a collection?

The official answer is that there is no limit on the number of items in SuperMemo (technical FAQs list the exact number that is somewhere in billions). I may add that there is a practical limit due total text size (2GB) or the file count in systems (8 milion). There fore, you may need to go plain text only to overcome the limit of 8 milion (assuming no sound or images are used). Then the limit is undefined, with an overall text size of 2GB.

#### What is the limit of nested hierarchy?

There is no fixed limit to the degree of nesting in the knowledge tree (or in the Ancestor window). Problems show up at unusually high numbers due to unknown bugs. The actual limit is 63 and comes from the fact that the indents are done with three whitepaces for the ancestors window, and are formatted with a procedure that accepts a maximum of 256 characters. This will be changed to 65,536 characters in the future (SM19+).

#### What is the limit of files in systems folder?

8 milion. You cna have up to 4 levels of hierachy. Therefore, you have 30 files at top level, 30*30 at second, 30*30*30 at third, and 30*30*30*30 at the forth level. That doe snot mean tha tthe limit is 8 milion html files, as images, sounds, style sheets, and binary file also count.

#### What is the maximum interval an element can have?

below 100 years. So, some items will be shcedule way after our life expectancy.

#### What is the maximum interval the user can set manually?

10,000 days. Ctrl+J is an artificial interval and setting it to 10,000 almost certainly implies forgetting. It should remain limited to prevent accidental scheduling of a repetition in the year 2222 (instead of 2022).

#### What is the maximum first interval an item can have in SM-18?

40 days.

The value of four weeks is just a rough estimate of the upper limit that might change from version to version (the limit is artificial as perfect recall, in theory, should result in infinite intervals)

in SuperMemo 16, maximum O-Factor is 20, which means that the maximum optimum interval is 20, but random dispersion may result in much longer intervals. The dispersion factor varies a lot across versions. Also the parameters of the normal distribution behind the dispersion vary. 38 days should be rare, but possible

#### What is the maximum optimal interval a collection can have?

33 days. It is capped by design.

#### What is the total text size limit?

Total text size in all SuperMemos from SuperMemo 9 (1998) through SuperMemo 18 is 2 GB.

#### What is the extension limit for topics?

There is Imports might be limited by hardware or Internet Explorer. SuperMemo gets specially slow for large topics, but there is no theoretical limit on the length of articles to paste. The absolute limit will be the same as the total size limit at 2GB. That is an article two billion characters long.

#### What is the limit on the number of clozes in Decompose?

The limit is 255 in older SuperMemos, 65535 in newer SuperMemos.

#### What is the maximum repetitions you can input manually in the Stats window?

10 milion. If you input anything greated that that, SuperMemo will replace it for exactly 100,000. Note that this metric is not limited at 10 milion, if you do more rpeetitions the count will keep increasing.

### What is the maximum element count that can be shceduled on a given day (newly outstanding)?

The limit is 65535 elements.

### Unkown limits

Maximum number of collections

Maximum repetitons for an item

Maximum links for an item.

Concept count limit?