Seconds (s)

The second is the SI base unit of time and the basis of all other time units.

Convert seconds to any time unit

1 second = 0.000011574074 days

Quick facts

Unit
Second (plural: seconds)
Symbol
s
Measures
Time / Duration
System
Everyday
Definition
9,192,631,770 periods of the radiation of the cesium-133 hyperfine transition.
Also written
sec, secs

1 second in other units

Days0.000011574074 d
Hours0.000277777778 h
Minutes0.01666666667 min
Years3.1688739 × 10-8 yr
Months3.8026486 × 10-7 mo
Weeks0.000001653439 wk
Milliseconds1,000 ms
Centuries3.1688739 × 10-10 c

What is a second?

The second is the SI base unit of time and the basis of all other time units. It was originally 1/86,400 of a mean solar day; since 1967 it has been defined by the frequency of a transition in cesium-133 atoms, measured by atomic clocks.

A second is roughly the time between two heartbeats at rest, or the time it takes to say "one thousand and one".

Where the second sits among time units

The second is number 21 of 101 on our scale of time units, ordered from smallest to largest.

Picosecond1 s = 1,000,000,000,000 ps Nanosecond1 s = 1,000,000,000 ns Microsecond1 s = 1,000,000 µs Millisecond1 s = 1,000 ms Secondthis unit Minute1 min = 60 s Hour1 h = 3,600 s Day1 d = 86,400 s Week1 wk = 604,800 s

What seconds are used for

  • Sports timing and records
  • Physics and engineering formulas
  • Computer timestamps (Unix time counts seconds since 1970)
  • Cooking and exercise timers

Seconds in real life

  • The 100 m world record is 9.58 seconds
  • Light travels about 300,000 km in one second
  • A resting heart beats about once per second
  • A day has 86,400 seconds

One second is about 3.3 blinks, or about 1.3 heartbeats, or about 50 hummingbird wingbeats, or about 10% of a 100 m sprint (world record).

Top second conversions

Common amounts of seconds

Convert seconds to all 100 other units

Everyday

Metric (SI)

Astronomical

Scientific

Historical & cultural

Everyday comparisons

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Frequently asked questions

What is a second?

The second is the SI base unit of time and the basis of all other time units.

How is the second defined?

9,192,631,770 periods of the radiation of the cesium-133 hyperfine transition.

How many days are in a second?

One second equals 0.000011574074 days.

How many hours are in a second?

One second equals 0.000277777778 hours.

How many minutes are in a second?

One second equals 0.01666666667 minutes.