Some delays or other time-based effects don’t offer the possibility to use beats per minute (BPM). The delay needs to be set in milliseconds. The BPM usually state how many quarter notes are played per minute. In order to find the duration of a quarter note, you need to convert the BPM to minutes.
The following formula applies:
¼ note (min) = 60 / BPM
The result is in minutes. In order to get milliseconds, you can use the following formula:
¼ note (ms) = 60000 / BPM
With the result you can calculate other note values as well.
The calculator makes this a lot easier: