Do the rest-hour rules still apply when the ship is in port?
Yes. STCW and MLC's rest-hour limits apply to hours of rest generally, not only while at sea — being alongside doesn't suspend the 10-hour daily or 77-hour weekly minimums. What changes in port is the pattern of work (cargo operations, maintenance, surveys, shore leave logistics), which is exactly when schedules tend to drift away from the rest-hour plan without anyone intending it to. Some administrations allow limited flexibility for specific in-port circumstances under national implementing law — check your flag state's guidance if you think that applies to you.
What about emergencies or drills?
Both frameworks give the master overriding authority to require any hours of work necessary for the immediate safety of the ship, persons on board, or cargo, or to give assistance to other ships or persons in distress. That override doesn't erase the obligation, though — once normal operations resume, the master has to ensure that anyone who lost rest during a scheduled rest period is given adequate compensatory rest afterwards. Routine drills, by contrast, are expected to be scheduled in a way that minimizes disruption to rest periods and doesn't induce fatigue — they aren't a blanket exception.
Is there really an exception allowing less than 77 hours of rest a week?
Some flag states permit limited exceptions to the weekly minimum and to the split-rest rule, typically through national legislation or an authorized collective bargaining agreement — for example, allowing weekly rest to be reduced to no less than 70 hours, for no more than two consecutive weeks, with the interval between two exception periods being no less than twice the length of the exception period, and the daily minimum never dropping below 6 hours even during an exception. These exceptions exist for genuinely exceptional operational circumstances, not as a routine scheduling tool, and not every flag state permits them at all. Check your flag state's specific rules before relying on one.
Does this calculator store or send my schedule anywhere?
No. Every calculation runs in your own browser using JavaScript — nothing you type is uploaded, logged, or sent to a server. You can check this yourself: the page works the same way with your device offline once it's loaded.
Can I use a result from this calculator as proof of compliance?
No. This is a reference and self-check tool, not an official rest-hour record and not a compliance certificate. Your company's approved recording system (see how that normally works) is what a Port State Control inspector will ask for. See the full disclaimer.
The fragmentation rule flagged my schedule, but my two rest blocks look fine to me. Why?
The "no more than two rest periods, one of at least six hours" rule is evaluated over rolling 24-hour periods anchored to when your rest periods actually start. If your total daily rest is genuinely split into three or more distinct periods, or neither period reaches six hours, it will be flagged. If you believe the result doesn't match your real schedule, double-check the exact start/end times you entered — small gaps you didn't intend (a few minutes here or there) can register as an extra, very short "period."
My flag state or union agreement has different numbers — can I still use this?
The calculator implements the STCW and MLC baseline numbers described on the STCW vs MLC page. Some flag states, companies, or collective agreements set stricter limits. If yours does, treat a "compliant" result here as the regulatory floor, not necessarily your actual limit — check your specific requirements too.