Cron Expression Explainer

How to use

1. Type or paste a five-field cron expression — minute, hour, day, month, weekday.
2. Read the plain-language explanation and check the next five scheduled runs calculated from right now.
3. Edit the expression and the explanation updates live — useful for writing a new crontab entry and verifying it does what you mean.

About this tool

A cron expression is five fields that tell a Unix scheduler when to run a job. The fields are minute, hour, day of the month, month and day of the week, in that order. An asterisk means every, a slash means every N, a comma lists values and a dash sets a range. The syntax is compact and unintuitive, which is why getting it wrong is a recurring source of incidents — a job that was supposed to run every hour runs every minute, or a backup that should fire on weekdays fires on Sunday.

This tool translates the five fields into a sentence you can read, and then shows the next five scheduled runs calculated from the current time. The runs are the real test: if the sentence sounds right but the next run is three months away, the expression is wrong. Editing the expression updates both in real time, so you can iterate until the schedule matches what you need.

The calculation runs in your browser using plain date arithmetic — no server, no cron daemon, no time zone conversion beyond what your browser already knows. It handles the standard five-field format used by crontab, Kubernetes CronJobs and most CI systems. It does not handle the sixth field (seconds) used by some Java schedulers, or the @yearly/@monthly shortcuts — write those in five-field form.

Frequently asked questions