CronJob Schedule Calculator
Parse a Kubernetes CronJob's 5-field cron schedule, list upcoming run times, and estimate overlap risk under the configured concurrency policy.
Inputs
Simplified: minutes between runs (e.g. */15 * * * * = 15).
Overlap Risk
false
Concurrency Policy Impact
No overlap expected — job duration fits within the interval.
Runs per Day
96
Upcoming Runs
0
Step by step
Runs per day
1440 ÷ 15
= 96
Overlap check
5min job vs 15min interval
= No overlap
How it works
A CronJob's schedule field uses standard 5-field cron syntax (minute hour day-of-month month day-of-week). This calculator uses a simplified fixed-interval model to project upcoming run times and, critically, checks whether the typical job duration exceeds the interval between runs — if it does, the concurrencyPolicy (Allow/Forbid/Replace) determines whether runs overlap, get skipped, or get replaced.
Formula
runsPerDay = floor(1440 / intervalMinutes)
- I
- Schedule interval in minutes
- R_d
- Number of runs per day
Frequently Asked Questions
What does concurrencyPolicy: Forbid actually skip?
If a previous Job is still running when the next scheduled time arrives, Forbid causes the controller to skip creating a new Job entirely for that scheduled slot — it does not queue it for later.
How many missed schedules does Kubernetes tolerate?
The startingDeadlineSeconds field bounds how late a missed run can start; if too many schedules are missed (more than 100 by default) the CronJob controller stops trying to catch up and logs an error instead of running a backlog.
Why use a simplified minute interval instead of full cron parsing?
Full 5-field cron (with irregular day-of-week/day-of-month combinations) doesn't reduce to a single fixed interval — this calculator models the common fixed-interval case (e.g. */N * * * *) directly used by most CronJobs.