You can display information about a card by using the Cards>Info menu item, or by right-clicking on the card and then selecting Info. Most of the displayed information should be self-explanatory. A few notes:
Only shown when the card is new, it shows the order the card will appear in relative to other new cards. The position can be changed in the browser.
The delay from one review to the next. Times are abbreviated; "0s, 1m, 3h, 4d, 5mo, 6y" refers to seconds, minutes, hours, days, months and years respectively.
The approximate amount the interval will grow when you answer a review card with the "Good" button.
The statistics window is accessed by clicking on Stats button at the top of the main window, or by pressing T. The statistics window will show statistics from the currently selected deck and any subdecks. If you click on "collection" on the bottom left, statistics will be shown for your entire collection instead. On 2.1.28+, additionally, you can display graphs for arbitrary searches by adding filters in the search box.
Anki 2.1.28+ introduces redesigned graphs. The old graphs are currently still accessible with a Shift-click on the Stats button.
For Anki 2.1.28+, by default Anki will show you statistics for the previous year. You can change this to all history scope or deck life scope at the top. (The "today" section at the top is of course unaffected by this selection.)
For older versions of Anki, by default Anki will show you statistics for the previous month. You can change this to a year scope or deck life scope at the bottom. (The “today” section at the top is of course unaffected by this selection.)
Clicking on "Save PDF" will save an PDF document of the statistics to a file on your desktop to make it easy to share your statistics with others.
When you delete notes, their review history is maintained in Anki. It will not be included when looking at statistics for a specific deck (as Anki has no way of knowing which deck the deleted cards belonged to), but will be included when you look at statistics for the whole collection.
The stats window uses some terms that you may not be familiar with:
A mature card is one that has an interval of 21 days or greater.
A young card is one that has an interval of less than 21 days, but is not in learning.
A learning card is one that is still in learning mode (using whatever steps may be defined in the deck’s options).
A relearning card is a card that you have failed in review mode, thus returning it to learning mode to be relearned.
An unseen card is one that has been added to your collection but has not yet entered learning mode. Unseen cards are sometimes referred to as "new" cards, especially when they are in the "new" queue to be shown for the first time.
At the top of the statistics window is a brief list of textual statistics about the reviews that you have completed today. A “review” in this context is 'one answering of a card', so a card might count as multiple reviews if it needed to be seen multiple times, and a learning card answered also counts as a “review.” A couple of the stats whose meaning may not be immediately obvious:
This is the number of reviews that you have failed (i.e., pressed Again on). The correct percentage listed afterwards is the number of cards you did 'not' fail divided by the total number of cards you studied.
Learn, Review, Relearn, Filtered
The number of reviews that were learning cards, review cards, relearning cards, or studied in a filtered deck when not due.
The stats for the current day are not a good overall indicator of your learning progress; everyone has bad days and good days, and seeing that you got a lower percentage correct on a particular day should not be cause for concern. The remainder of the stats, which take longer periods of time into account, will give more useful information if you wish to try to change your study habits or scheduling settings based on your performance.
The “today” statistics are unaffected by the time period selected at the bottom of the window.
This graph shows an estimated number of reviews that will be due on a given day in the future if you learn no new cards and fail no cards. The bars and the left axis show the number of cards due on each day if you study all cards each day, while the line and the right axis show the number of cards due on that day if you don’t study at all until then. Note that the forecast graph does not count reviews that are currently overdue, so if you have a large backlog, the overdue cards will not be displayed.
This graph counts the number of card reviews you have done. The bars may correspond to days, weeks, or months, depending on the time period you’ve selected at the bottom of the screen. The differently colored blocks show how many of the cards you answered on each day were mature, young, relearning, or learning cards. There is also a separate group for cards answered in a filtered/cram deck while they were not due. The line and the right axis shows the cumulative total for each type of review as time progresses across the graph (so at 0 days, it would display the number for the entire time period displayed on the graph).
This graph works exactly like Review Count, except that it deals with the amount of time you spent on each card rather than the number of cards answered.
This graph displays the number of cards that have a given interval (the delay between two reviews). The line and the right axis tell you what percentage of your cards have an interval of less than or equal to the time below that point. The time scope has a different effect on this graph than other graphs: rather than changing which cards or period of studying is included, it limits how far out the intervals are displayed to (so 14-month intervals are not displayed at all on a 1-year graph).
This graph shows what percentage of total reviews you have passed (i.e., not pressed Again on) during given hours. The larger, darker bars and left axis show the success rate; the thinner, lighter bars and right axis show the number of reviews you’ve made at that hour (so you know how significant the results are).
This graph shows how many times you’ve chosen the Again, Hard, Good, or Easy button while studying learning/new, young, and mature cards. Anki also displays the percentage of correct reviews for each type of card.
This pie chart shows what percentage of your deck or collection consists of mature, unseen, young/learn, and suspended cards. If you wish to calculate a more precise percentage, the key shows the exact number of cards in each section, and the total number of cards is displayed to the side.
If you’re interested in getting information from your statistics other than what Anki provides, it is possible to access the data directly. Because of the complexity involved, this is not something we can provide any support for.
One option is to write an add-on that adds another graph or more details to the statistics window. There are several add-ons of this sort on AnkiWeb already, which you can look at to get an idea of how it works.
A more powerful and more complex option is to extract the review log information directly from Anki’s database and analyze it in an external program. Anki uses a database format called SQLite. There are many tools available for working with SQLite databases; one of the easiest to start with is called SQLite Browser, which will allow you to look around the database as well as export a CSV version of tables for import into another program.
The most important table for statistics is the 'revlog' table, which stores an entry for each review that you conduct. The columns are as follows:
The time at which the review was conducted, as the number of milliseconds that had passed since midnight UTC on January 1, 1970. (This is sometimes known as 'Unix epoch time', especially when in straight seconds instead of milliseconds.)
The ID of the card that was reviewed. You can look up this value in the id field of the 'cards' table to get more information about the card, although note that the card could have changed between when the revlog entry was recorded and when you are looking it up. It is also the millisecond timestamp of the card’s creation time.
This column is used to keep track of the sync state of reviews and provides no useful information for analysis.
Which button you pressed at the end of the review (1 for Again, 4 for Easy).
The new interval that the card was pushed to after the review. Positive values are in days; negative values are in seconds (for learning cards).
The interval the card had before the review. Cards introduced for the first time have a last interval equal to the Again delay.
The new ease factor of the card in permille (parts per thousand). If the ease factor is 2500, the card’s interval will be multiplied by 2.5 the next time you press Good.
The amount of time (in milliseconds) you spent on the question and answer sides of the card before selecting an ease button.
This is 0 for learning cards, 1 for review cards, 2 for relearn cards, and 3 for early "cram" cards (cards being studied in a filtered deck when they are not due).