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Cron Expression Next Run Calculator

Work out cron expression next run instantly with clear inputs, formula shown and shareable results.

About Cron Expression Next Run Calculator

A cron expression like */15 fires at minutes that are multiples of the interval within each hour, so the next run is the next such boundary rather than the interval counted from now. The failure mode worth checking is overlap: cron starts a new instance on schedule regardless of whether the previous one finished, so any job whose duration approaches the interval needs a lock.

Formula

Next cron slot

next slot = ceil((current minute + 1) / interval) x interval; runs per day = floor(1440 / interval)

Worked example

With the default values below, Cron Expression Next Run Calculator returns Minutes until the next run of 8. Change any input above and every figure here is recalculated in your browser.

Inputs used

Run every N minutesaccepts 1–1,440
15
Current minute of the houraccepts 0–59
37
Job durationminimum 0.01 min
4 min
Current houraccepts 0–23
14

Results

Minutes until the next run
8 min
Next run time
14:45
Runs per day
96
Overlap risk
No overlap at this duration

Step by step

  1. 1Values used
  2. 2Next cron slot
  3. 3Minutes until the next run= 8 min
  4. 4Next run time= 14:45
  5. 5Runs per day= 96
  6. 6Overlap risk= No overlap at this duration

Assumptions and limits

  • The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to whole numbers, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

Why does */7 behave oddly?

Step values restart each hour, so */7 fires at minutes 0, 7, 14, 21, 28, 35, 42, 49 and 56 — the gap between 56 and the next hour's 0 is only 4 minutes.

How do I prevent overlapping runs?

Wrap the command in flock with a lock file, or use a systemd timer, which will not start a service that is still running.

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