About this tool
The Cron Expression Builder helps you create and decode Unix cron schedules. Edit fields visually or paste a full expression. See a plain-English description and the next 5 run times. Includes common presets for quick setup.
Cron expression cheat sheet
A cron expression is a 5-field schedule. Each field accepts a number, a list (comma-separated), a range (a-b), a step (* /n), or special wildcards.
| Field | Position | Allowed values | Special chars |
|---|---|---|---|
| Minute | 1st | 0-59 | * , - / |
| Hour | 2nd | 0-23 | * , - / |
| Day of month | 3rd | 1-31 | * , - / ? |
| Month | 4th | 1-12 or JAN-DEC | * , - / |
| Day of week | 5th | 0-6 or SUN-SAT (0=Sun) | * , - / ? |
What the special characters mean
Every field accepts the same four operators. Combine them freely: 0,30, 9-17, and */15 can all sit in one field.
| Char | Name | Meaning | Example in minute field |
|---|---|---|---|
| * | asterisk | every value in the field | * = every minute |
| , | comma | a list of specific values | 0,15,30,45 = 4 times an hour |
| - | hyphen | an inclusive range | 0-9 = minutes 0 through 9 |
| / | slash | a step, paired with * or a range | */5 = every 5th minute |
Worked example: reading 0 9 * * 1-5
The default expression in the tool is 0 9 * * 1-5. Read it field by field, left to right:
9 → hour 9 (09:00, 24-hour clock)
* → every day of the month
* → every month
1-5 → Monday through Friday (1=Mon, 5=Fri)
Joined together that reads "at 09:00, Monday through Friday", which is why it is the classic weekday-morning job. Swap the hour for 17 to fire at 5pm instead, or change 1-5 to 1,3,5 to run only Monday, Wednesday, and Friday. The Schedule panel above restates any expression in plain English and lists the next 5 run times so you can sanity-check before deploying.
Common cron patterns
| Schedule | Cron expression |
|---|---|
| Every minute | * * * * * |
| Every 5 minutes | */5 * * * * |
| Every hour on the hour | 0 * * * * |
| Every day at midnight UTC | 0 0 * * * |
| Every weekday at 9am | 0 9 * * 1-5 |
| Twice a day (8am, 8pm) | 0 8,20 * * * |
| First of the month at midnight | 0 0 1 * * |
| Every Sunday at 2:30am | 30 2 * * 0 |
| Last Friday of the month | 0 0 * * 5L (Quartz only - not in standard cron) |
| Every 15 min during business hours, Mon-Fri | */15 9-17 * * 1-5 |
Pitfalls
- Timezone - most cron daemons run in the server's local time. If the server is UTC, "every day at 9am" runs at 9am UTC. Specify the timezone in your scheduler (Kubernetes CronJob supports timeZone, GitHub Actions runs in UTC).
- Day of month AND day of week - if both are set (not *), standard cron runs when EITHER matches. Quartz runs when BOTH match. Test before depending.
- Step from non-zero start -
5/10 * * * *means start at minute 5, then every 10 minutes (5, 15, 25...). Many people expect it to mean "every 5 minutes after minute 10", which is wrong. - DST transitions - schedules at 2:00-3:00am in DST-observing timezones either skip (spring forward) or run twice (fall back). Avoid this window for critical jobs.
Cron vs alternatives
- systemd timers - more powerful (calendar events, persistence after sleep, dependencies). Standard on modern Linux.
- at - one-shot scheduling.
echo "task" | at 5pm tomorrow. - Kubernetes CronJob - cron syntax with cluster-level scheduling, retry policies, history.
- GitHub Actions / GitLab CI - same cron syntax for repository-level scheduled workflows. Runs in UTC.
- AWS EventBridge - cron + rate() expressions. Cron has 6 fields (adds year).
Scheduling work usually pairs with other developer utilities. Convert a run timestamp from your logs to a readable date with the Unix timestamp converter, validate the JSON or config a scheduled job writes using the JSON formatter and validator, and prototype the field patterns a parser will accept with the live regex tester.
Frequently asked questions
Does 0 0 * * 0 mean every Sunday or Saturday?
Sunday. Standard cron uses 0=Sunday, 6=Saturday. Some dialects accept 7 for Sunday for backward compatibility.
What timezone is my cron running in?
By default, the server's system timezone. Check with `date` or `timedatectl`. Cloud schedulers (GitHub Actions, Kubernetes CronJob, AWS) usually default to UTC.
How do I run a job every 90 minutes?
Standard cron can't express it directly. Use 0 0,3,6,9,12,15,18,21 * * * (every 3 hours) and gate inside the job, or use a systemd timer with OnCalendar=*-*-* 00,01:30:00 stepping.
Does cron catch missed jobs after a reboot?
Standard cron does not. anacron does for daily/weekly/monthly. systemd timers with Persistent=true run missed instances after boot.
Are cron expressions case-sensitive?
Numbers no. Names yes - use MON or mon consistently. Most parsers accept either.
How accurate is the Cron Expression Builder?
It applies the standard formula. Accuracy is limited only by your input precision. For decisions with material consequences (taxes, medical, legal, structural), use the result as a starting point and verify with a qualified professional in the relevant field.
Is the Cron Expression Builder free to use?
Yes. 100% free, no signup, no payment, no API key. The site is funded by display ads around the tool but not inside the calculation flow.
Are my inputs saved anywhere?
No. All inputs stay in your browser tab. Closing the tab discards them. The site uses Google Analytics for traffic measurement (anonymized) but the analytics never see what you type into the form.
Can I use the Cron Expression Builder on my phone?
Yes. The tool is responsive and tested on iOS Safari, Android Chrome, and major desktop browsers. Touch targets meet Apple's 44pt and Google's 48dp minimum.
Does the Cron Expression Builder work offline?
Yes. Once the page has loaded, it works without internet. The calculation runs in JavaScript on your device.
How do I report a bug or suggest improvement to the Cron Expression Builder?
Email hi@3tej.com with the URL of this page and a description of what you saw vs expected. We typically respond within 72 hours.
Can I share results from the Cron Expression Builder?
Take a screenshot or copy the output. The page doesn't generate shareable URLs for specific calculations - inputs stay in your browser only.
Why are the results different from another cron expression builder tool?
Most likely: different formula assumptions, different default values, different rounding rules, or different applicable rates. Check the methodology if both tools document it. Both can be valid for different scenarios.