Crontab Next Run Calculator

About this calculator

A standard Unix crontab expression uses five space-separated fields — minute, hour, day-of-month, month, and day-of-week — each accepting numbers, ranges, lists, wildcards (*), and step values (like */15 for every 15 units) to define a recurring schedule, such as “0 3 * * 1-5” for 3 AM on weekdays. Working out exactly when such an expression will next fire requires parsing all five fields and simulating time forward, which is easy to get wrong by hand, especially with step values or day-of-week/day-of-month interactions.

Sysadmins, backend developers, and DevOps engineers use this calculation whenever they write or review a cron job — for scheduled backups, log rotation, batch data processing, or automated deployments — to confirm the schedule actually matches what they intended before it runs unattended on a production server.

This calculator parses your 5-field crontab expression against a base UTC time and lists the next several scheduled run times, letting you catch a mistyped cron line before it causes a job to run at 3 AM instead of 3 PM, or every minute instead of every hour.