Hours to Seconds (h to s)

How to convert hours to seconds

Multiply the hours by 3,600:

s = h × 3,600

2.5 h × 3,600 = 9,000 s. The factor comes from 60 minutes in an hour and 60 seconds in a minute: 60 × 60 = 3,600. If you have hours and minutes, convert both and add: 1 h 15 min is 3,600 + 15 × 60 = 4,500 s, the same as entering 1.25 hours. To go the other way, divide by 3,600; for minutes, see hours to minutes and minutes to seconds.

Hours to seconds chart

Days, weeks and years in seconds

Seconds are the unit computers and timers count in, so these numbers turn up in settings: a cache that expires in 86,400 s lasts a day, and a session timeout of 28,800 s is eight hours. For longer spans, days to seconds goes straight from days.

When an hour is not 3,600 seconds

The conversion itself is exact, but clock days are not always 24 hours long. On the Sunday in March when daylight saving time starts, a U.S. clock day has 23 hours (82,800 s); on the Sunday in November when it ends, 25 hours (90,000 s). Rarely, a leap second has been added to official time, making a minute of 61 seconds; the last one was at the end of 2016, and in 2022 the international General Conference on Weights and Measures decided to stop adding them by 2035. For timing an event between two clock readings, the time duration calculator handles the dates for you.

Hours and minutes in one figure

Timesheets, video lengths and race results often mix units. Convert each part and add: 2 h 40 min is 2 × 3,600 + 40 × 60 = 9,600 s, and 1 h 05 min 30 s is 3,600 + 300 + 30 = 3,930 s. Going back, divide by 3,600 for the whole hours, then the remainder by 60 for minutes: 9,600 s is 2 h with 2,400 s left, and 2,400 ÷ 60 = 40 min. Physics problems usually want seconds, because speeds are given per second: a car at 60 mph covers 88 feet each second, so in 2.5 hours, or 9,000 seconds, it travels 792,000 feet — 150 miles.