Cron Builder & Next-Run Preview

Build a standard 5-field cron expression (minute hour day-of-month month day-of-week) with presets or the field-by-field builder below, or just type/paste one directly — either way, this computes and validates the real thing: the actual next 10 run times, not just a description of what each field means. For that instead, see the Cron Expression Explainer. Runs entirely in your browser; nothing is sent anywhere.

How day-of-month and day-of-week interact

Standard cron has a real, commonly-confusing quirk this tool applies correctly: if both day-of-month and day-of-week are restricted (anything other than *), a day matches when either one matches, not when both do — so 0 0 1,15 * 1 runs on the 1st, the 15th, and every Monday, not only on a Monday that happens to also be the 1st or 15th. If only one of the two fields is restricted, only that one is checked, as you'd expect. This tool's next-run preview always reflects this real behavior rather than a simplified AND-only approximation.

Field syntax supported

Each field accepts * (every value), a single number, a comma-separated list (1,15,30), a range (1-5), a step (*/15), or a stepped range (1-30/5) — and combinations of these separated by commas (1-5,10,*/15). Day-of-week accepts both 0 and 7 for Sunday. Ranges/values outside a field's valid bounds, malformed steps, and expressions with other than exactly 5 fields are all caught and explained rather than silently misread.