Accuracy is a measurement of a player's consistency. There are three types of accuracy that a player can have. One of them being the beatmap's accuracy which is dependent on hit scores gained. Another being the player's overall accuracy that is weighed to allow better scores to stand out more. And lastly, the player's Performance Points (pp) accuracy which is dependent on the submitted score's accuracy.
Accuracy formula for osu!standard
In osu!standard, accuracy is calculated by weighting the judgement gained from each hit object by its value and divided by the maximum possible amount.
Reference for one hit circle:
300 -> 300 / 300 = 1 = 100.00% 100 -> 100 / 300 = 1/3 = 33.00% 50 -> 50 / 300 = 1/6 = 16.67% 0 -> 0 / 300 = 0 = 0.00%
Accuracy formula for osu!taiko
In osu!taiko, accuracy is calculated by taking the sum of the note accuracy divided by the number of notes. The note accuracy are as follows: a GREAT (良) counts as 100%, GOOD (可) as 50% (half), and MISS/BAD (不可) as 0% (which also breaks the combo). Drum rolls and spinners do not influence the accuracy.
Accuracy formula for osu!catch
In osu!catch, accuracy is calculated by taking the total of non-spinner hit objects collected divided by the total number of non-spinner objects. All hit objects have the same value, except for bananas, as they are part of the spinner object.
Note for API users: To calculate the accuracy in osu!catch, number of droplets are under
count50 and number of missed droplets are under
Accuracy formula for osu!mania
In osu!mania, accuracy is calculated similarly to osu!standard.
The performance graph is a chart that displays the player's performance (based on their life bar) over the course of a play (time). Additional information can be shown when hovering the in-game cursor over it.
Note: The additional information can only be viewed after playing a beatmap or watching an exported replay. After exiting the results screen, this information will not be saved.
When hovering over the performance graph, a tooltip is displayed with an Error and Unstable Rate.
Due to the way the DT (Double Time) and HT (Half Time) mods are implemented, the error and unstable rate values will be multiplied by the same factor as the song. To get the true values when playing DT, divide the results by 1.5. Similarly, multiply the results by 1.33 when playing HT.
Error will always display two values which represents how far off the early hits were on average and how far off the late hits were on average. The higher the Overall Difficulty value of the beatmap is, the lower the Error values will have to be to do well when playing the beatmap.
Unstable rate represents the consistency of the timing of the hits, where lower numbers are better (top players often score below 100). Note that the value measures consistency, not accuracy, so consistently in hitting 15ms early is the same as consistently in hitting "on time." The formula is essentially the standard deviation of the hit errors (in milliseconds) multiplied by 10. Sample code is available as reference, showing how osu-stable calculates unstable rate.
Note: Spin is only used for osu!standard.
In addition to the accuracy, some information regarding spinners is also seen in the same tooltip.
Speed represents the average RPM (revolutions per minute) on all the spinners in the beatmap. Max is the highest RPM achieved in any of the beatmap's spinners.