Using LCM for repeating schedules
Find the next shared cycle when events start together.
By the ClearLCM team · Updated November 3, 2026
A simple timing example
Suppose one reminder repeats every 6 minutes and another every 8 minutes. Both run now. The first reminder repeats at 6, 12, 18 and 24 minutes; the second at 8, 16 and 24 minutes. They next coincide after 24 minutes because LCM(6, 8) = 24. To add a third reminder repeating every 10 minutes, compute LCM(6, 8, 10) = 120.
Keep the units consistent
Convert all intervals to the same unit before entering them. A 2-hour cycle and a 90-minute cycle can be represented as 120 and 90 minutes. Their LCM is 360 minutes, or 6 hours. Entering 2 and 90 without conversion instead solves a different problem. For fractional intervals, such as 1.5 minutes, scale every interval into whole seconds before calculating.
Check the assumptions
The basic LCM method assumes all cycles start together and continue at fixed intervals. Different starting offsets require an additional alignment calculation; the LCM alone does not tell you when they first meet. Real calendar months also have different lengths, and daylight-saving changes complicate wall-clock schedules. Use the calculator for consistent intervals and verify any real scheduling constraints separately. It is a mathematical planning aid, not a calendar or reminder service.
Put the example into practice with the free least common multiple calculator.