Convert Second to Day (s → d)

Converting seconds to days is straightforward: multiply by the conversion factor. Follow these three steps to do it by hand or in your head.

1. 1
   Take your value in seconds

   Start with the number of seconds (s) you want to convert.
2. 2
   Multiply by 0.00001157

   The conversion factor from s to d is 0.00001157. Multiply your value by this number.
3. 3
   Read the result in days

   The result is your value in days (d).

Multiply the value in seconds by 0.00001157. For the reverse direction, multiply by 86,400.

• ✓60 s = 1 minute; 3600 s = 1 hour; 86,400 s = 1 day.
• ✓For sub-second intervals use ms (milliseconds), µs (microseconds) and ns (nanoseconds).
• ✓The symbol is s (lowercase). "sec" is informal.

• ✗Writing S instead of s for the second.
• ✗Confusing second of time with second of arc in astronomy.
• ✗Assuming microsecond and millisecond are similar — 1 ms = 1000 µs.

What is the Second?

The second is the base SI unit of time. Since 1967, it has been defined by atomic physics: the duration of 9,192,631,770 periods of the radiation corresponding to the transition between two hyperfine levels of the ground state of the cesium-133 atom. This makes the second extraordinarily reproducible — modern atomic clocks based on optical transitions can keep time to a few parts in 10¹⁸. The second is the foundation of all time measurements: the minute (60 s), the hour (3,600 s), the day (86,400 s). It is also fundamental in physics — speeds (m/s), accelerations (m/s²), frequencies (Hz = 1/s), and Planck's constant all reference the second. International civil time, GPS, and the internet's time synchronization all depend on cesium-based atomic seconds. The second relates to the millisecond (1,000 ms = 1 s), the microsecond, and the nanosecond.

• Everyday timekeeping
• Scientific and engineering measurements
• Sports timing (100 m sprint in ~10 s)

What is the Day?

The day equals exactly 86,400 seconds (24 hours) — the mean time for Earth to complete one rotation relative to the Sun (the 'solar day'). The 'sidereal day' (relative to distant stars) is about 4 minutes shorter at 23 hours, 56 minutes, 4 seconds, but everyday usage refers to the solar day. Days are the fundamental unit of human routine: sleep cycles, work schedules, calendar appointments, and project timelines all measure in days. The day relates to the second (86,400 s = 1 day), the hour (24 h = 1 day), and the week (7 days = 1 week). Earth's rotation gradually slows due to tidal friction, lengthening the day by about 1.7 milliseconds per century — leap seconds are occasionally added to civil time to compensate, though this practice will end by 2035 by international agreement.

• Calendar dates and scheduling
• Shipping and delivery times
• Medical dosing intervals (e.g. "once daily")