Ship's Watches to Hours (watch to h)

1 ship's watch equals 4 hours exactly.

1 ship's watch = 4 hours

How to convert ship's watches to hours

To convert ship's watches to hours, multiply the number of ship's watches by 4. This factor is exact. To go the other way, multiply hours by 0.25.

hours = ship's watches × 4

Example: 10 ship's watches = 40 hours.

Months and years are not constant. This site uses the average Gregorian year of 365.2425 days, so one 'year' converts to 365.2425 days, not 365; use 'common year' for exactly 365 days.

About these units

Ship's Watch (watch)

NauticalTraditional unit (still used in some regions)

Four hours, the standard duty period at sea. The 'dog watches' of the evening are split into two hours each.

Naval and merchant crews divide the day into watches so that the ship is never left unattended. A normal watch lasts four hours, and its length is the basis for the figure used here, 14,400 seconds. The traditional scheme described by Wikipedia had five four-hour watches and two two-hour dog watches, named the first, middle, morning, forenoon and afternoon watches, with the afternoon watch ending at 1600.

Splitting the 1600 to 2000 period into a first and second dog watch gives an odd number of watches per day, so each crew member's schedule shifts from day to day, and it also lets everyone eat an evening meal. Time on board is marked with the ship's bell, struck every half hour so that eight bells ends a four-hour watch. Merchant ships typically keep six four-hour watches instead, which makes the pattern consistent.

1 ship's watch = 14,400 seconds (exactly).

Sources: Wikipedia: Watchkeeping; Wikipedia: Ship's bell

Hour (h)

Metric (SI)Current unit

60 minutes or 3,600 seconds, one twenty-fourth of a mean solar day.

Egyptian astronomers gave us the twelve. Coffin lids from about 2150 BC show the night divided into exactly 12 intervals, tied to the rising of star groups called decans, and the day was later split into 12 hours with sundials. These were seasonal hours, a twelfth of the daylight, so a summer hour was longer than a winter one. The word itself comes from Greek hora, originally any span of time, through Latin and Old French into English in the 13th century.

Equal hours of 1/24 of a day were probably first proposed by Hipparchus, and mechanical clocks made them the practical choice, since a clock showing seasonal hours had to be readjusted every morning and evening. Today the hour is exactly 3,600 seconds and is a non-SI unit accepted for use with the SI. Civil time still bends it a little: UTC hours have lasted 3,601 seconds 27 times since 1972 to keep clocks within 0.9 seconds of the Earth's rotation. In practice we use it for working shifts, travel times and electricity bills measured in kilowatt-hours.

1 hour = 3,600 seconds (exactly).

Sources: Wikipedia: Hour; BIPM: SI Brochure, 9th edition

Related conversions

See all time units.