STCW: built around watchkeeping and fatigue
The STCW Convention (Standards of Training, Certification and Watchkeeping for Seafarers) is an IMO instrument. Its rest-hour provisions live in Regulation VIII/1 and Section A-VIII/1 of the STCW Code, added by the 2010 Manila Amendments. STCW's rest requirements are aimed specifically at seafarers assigned watchkeeping duties, plus those with designated safety, security, or pollution-prevention duties — the roles where fatigue has an immediate, direct safety consequence.
STCW only ever works one way: it sets minimum hours of rest. There's no alternative "maximum hours of work" option under STCW — the convention's whole premise is that watchkeepers need a guaranteed floor of recovery time.
MLC 2006: every seafarer, with a choice built in
The Maritime Labour Convention, 2006 (MLC) is an ILO instrument, sometimes called the "seafarers' bill of rights." Its Regulation 2.3 and Standard A2.3 cover hours of work and rest for all seafarers on a ship covered by the convention — not just watchkeepers. That's the headline difference: MLC's scope is the whole crew, including catering, hotel, and other non-watchkeeping departments on cruise ships.
MLC also does something STCW doesn't: it lets each flag state (Member) decide whether to regulate through a minimum hours of rest limit or a maximum hours of work limit. Most flag states use the minimum-rest option, with numbers identical to STCW's. A smaller number apply the maximum-work alternative instead.
The numbers, side by side
| Rule | STCW (watchkeepers) | MLC — minimum rest option | MLC — maximum work option |
|---|---|---|---|
| Daily limit | ≥ 10h rest / 24h | ≥ 10h rest / 24h | ≤ 14h work / 24h |
| Weekly limit | ≥ 77h rest / 7 days | ≥ 77h rest / 7 days | ≤ 72h work / 7 days |
| Split rest | Max 2 periods, one ≥ 6h | Max 2 periods, one ≥ 6h | Not applicable |
| Max gap between rest | 14h | 14h | Not applicable |
| Who it covers | Watchkeepers & designated safety/security/pollution-prevention duties | Every seafarer on board | Every seafarer on board |
Use the calculator to check a schedule against whichever of these three the framework applies to you — the same tool, three sets of rules.
Why both usually apply at once
A cruise-ship deck officer, for instance, is a watchkeeper (STCW applies) and also a seafarer covered by the ship's Maritime Labour Certificate (MLC applies). When the numbers are identical — which they are for the minimum-rest option — this is academic: one set of records satisfies both. It matters more for crew who are not watchkeepers: a bar steward or laundry worker isn't covered by STCW's rest provisions at all, but is fully covered by MLC's, watchkeeper or not.
It also matters at the enforcement level. STCW compliance is verified against the ship's Safe Manning Document and watchkeeping arrangements; MLC compliance is verified against the ship's Maritime Labour Certificate and Declaration of Maritime Labour Compliance (DMLC) Parts I and II, which set out how the company actually meets Regulation 2.3 on that particular ship. Port State Control inspectors check both — see what happens when they don't like what they find.
A quick way to think about it
STCW asks "is this specific watchkeeper rested enough to stand a safe watch?" MLC asks "is every seafarer on this ship being treated within the working-time limits this flag state has committed to?" On paper the STCW numbers are a subset of the MLC minimum-rest numbers. In practice, most seafarers just need to meet one set of thresholds — the numbers in the two left-hand columns above are the same.